Articles de revues : « Atlantic Ocean Region »

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Walter, S., H. W. Bange, U. Breitenbach et D. W. R. Wallace. « Nitrous oxide in the North Atlantic Ocean ». Biogeosciences Discussions 3, n^o 4 (17 juillet 2006) : 993–1022. http://dx.doi.org/10.5194/bgd-3-993-2006.

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Abstract. In order to investigate the role of the North Atlantic Ocean as a source of atmospheric nitrous oxide and to decipher the major formation pathways of nitrous oxide, measurements of dissolved nitrous oxide were made during three cruises in the tropical, subtropical and subpolar North Atlantic in October/November 2002, March/April 2004, and May 2002, respectively. Nitrous oxide was close to equilibrium or slightly supersaturated in the surface layers suggesting that the North Atlantic acts as a weak source of nitrous oxide to the atmosphere. Depth profiles showed supersaturation throughout the water column with a distinct increasing trend from the subpolar to the tropical region. Lowest nitrous oxide concentrations, near equilibrium and with an average of 11.0±1.7 nmol L−1, were found in the subpolar North Atlantic where the profiles showed no clear maxima. Highest values up to 37.3 nmol L−1 occurred in the tropical North Atlantic with clear maxima at approximately 400 m. A positive correlation of nitrous oxide with nitrate, as well as excess nitrous oxide with AOU, was only observed in the subtropical and tropical regions. Therefore, we conclude that the formation of nitrous oxide occurs in the tropical region rather than in the subpolar region of the North Atlantic and suggest nitrification is the dominant formation pathway in the subtropical and tropical regions.

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Formetta, Giuseppe, Jonghun Kam, Sahar Sadeghi, Glenn Tootle et Thomas Piechota. « Atlantic Ocean Variability and European Alps Winter Precipitation ». Water 13, n^o 23 (30 novembre 2021) : 3377. http://dx.doi.org/10.3390/w13233377.

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Winter precipitation (snowpack) in the European Alps provides a critical source of freshwater to major river basins such as the Danube, Rhine, and Po. Previous research identified Atlantic Ocean variability and hydrologic responses in the European Alps. The research presented here evaluates Atlantic Sea Surface Temperatures (SSTs) and European Alps winter precipitation variability using Singular Value Decomposition. Regions in the north and mid-Atlantic from the SSTs were identified as being tele-connected with winter precipitation in the European Alps. Indices were generated for these Atlantic SST regions to use in prediction of precipitation. Regression and non-parametric models were developed using the indices as predictors and winter precipitation as the predictand for twenty-one alpine precipitation stations in Austria, Germany, and Italy. The proposed framework identified three regions in the European Alps in which model skill ranged from excellent (West Region–Po River Basin), to good (East Region) to poor (Central Region). A novel approach for forecasting future winter precipitation utilizing future projections of Atlantic SSTs predicts increased winter precipitation until ~2040, followed by decreased winter precipitation until ~2070, and then followed by increasing winter precipitation until ~2100.

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Dong, Shenfu, Silvia Garzoli et Molly Baringer. « The Role of Interocean Exchanges on Decadal Variations of the Meridional Heat Transport in the South Atlantic ». Journal of Physical Oceanography 41, n^o 8 (1 août 2011) : 1498–511. http://dx.doi.org/10.1175/2011jpo4549.1.

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Abstract The interocean exchange of water from the South Atlantic with the Pacific and Indian Oceans is examined using the output from the ocean general circulation model for the Earth Simulator (OFES) during the period 1980–2006. The main objective of this paper is to investigate the role of the interocean exchanges in the variability of the Atlantic meridional overturning circulation (AMOC) and its associated meridional heat transport (MHT) in the South Atlantic. The meridional heat transport from OFES shows a similar response to AMOC variations to that derived from observations: a 1 Sv (1 Sv ≡ 106 m3 s−1) increase in the AMOC strength would cause a 0.054 ± 0.003 PW increase in MHT at approximately 34°S. The main feature in the AMOC and MHT across 34°S is their increasing trends during the period 1980–93. Separating the transports into boundary currents and ocean interior regions indicates that the increase in transport comes from the ocean interior region, suggesting that it is important to monitor the ocean interior region to capture changes in the AMOC and MHT on decadal to longer time scales. The linear increase in the MHT from 1980 to 1993 is due to the increase in advective heat converged into the South Atlantic from the Pacific and Indian Oceans. Of the total increase in the heat convergence, about two-thirds is contributed by the Indian Ocean through the Agulhas Current system, suggesting that the warm-water route from the Indian Ocean plays a more important role in the northward-flowing water in the upper branch of the AMOC at 34°S during the study period.

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Walter, S., H. W. Bange, U. Breitenbach et D. W. R. Wallace. « Nitrous oxide in the North Atlantic Ocean ». Biogeosciences 3, n^o 4 (1 décembre 2006) : 607–19. http://dx.doi.org/10.5194/bg-3-607-2006.

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Abstract. In order to get a comprehensive picture of the distribution of nitrous oxide (N2O) in the North Atlantic Ocean, measurements of dissolved nitrous oxide were made during three cruises in the tropical, subtropical and cold-temperate North Atlantic Ocean in October/November 2002, March/April 2004, and May 2002, respectively. To account for the history of atmospheric N2O, we suggest a new depth-dependent calculation of excess N2O (ΔN2O). N2O depth profiles showed supersaturation throughout the water column with a distinct increasing trend from the cold-temperate to the tropical region. Lowest nitrous oxide concentrations, near equilibrium and with an average of 11.0±1.7 nmol L−1, were found in the cold-temperate North Atlantic where the profiles showed no clear maxima. Highest values up to 37.3 nmol L−1 occurred in the tropical North Atlantic with clear maxima at approximately 400 m. A positive correlation of nitrous oxide with nitrate, as well as excess nitrous oxide with the apparent oxygen utilization (AOU), was only observed in the subtropical and tropical regions. Therefore, we conclude that the formation of nitrous oxide via nitrification occurs in the tropical region rather than in the cold-temperate region of the North Atlantic Ocean

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Yu, Wei, Weiqing Han et David Gochis. « Influence of the Madden–Julian Oscillation and Intraseasonal Waves on Surface Wind and Convection of the Tropical Atlantic Ocean ». Journal of Climate 25, n^o 23 (1 décembre 2012) : 8057–74. http://dx.doi.org/10.1175/jcli-d-11-00528.1.

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Abstract Atmospheric intraseasonal variability in the tropical Atlantic is analyzed using satellite winds, outgoing longwave radiation (OLR), and reanalysis products during 2000–08. The analyses focus on assessing the effects of dominant intraseasonal atmospheric convective processes, the Madden–Julian oscillation (MJO), and Rossby waves on surface wind and convection of the tropical Atlantic Ocean and African monsoon area. The results show that contribution from each process varies in different regions. In general, the MJO events dominate the westward-propagating Rossby waves in affecting strong convection in the African monsoon region. The Rossby waves, however, have larger contributions to convection in the western Atlantic Ocean. Both the westward- and eastward-propagating signals contribute approximately equally in the central Atlantic basin. The effects of intraseasonal signals have evident seasonality. Both convection amplitude and the number of strong convective events associated with the MJO are larger during November–April than during May–October in all regions. Convection associated with Rossby wave events is stronger during November–April for all regions, and the numbers of Rossby wave events are higher during November–April than during May–October in the African monsoon region, and are comparable for the two seasons in the western and central Atlantic basins. Of particular interest is that the MJOs originating from the Indo-Pacific Ocean can be enhanced over the tropical Atlantic Ocean while they propagate eastward, amplifying their impacts on the African monsoon. On the other hand, Rossby waves can originate either in the eastern equatorial Atlantic or West African monsoon region, and some can strengthen while they propagate westward, affecting surface winds and convection in the western Atlantic and Central American regions.

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Bremer, Jaime R. Alvarado, Allan J. Baker et Jaime Mejuto. « Mitochondrial DNA control region sequences indicate extensive mixing of swordfish (Xiphias gladius) populations in the Atlantic Ocean ». Canadian Journal of Fisheries and Aquatic Sciences 52, n^o 8 (1 août 1995) : 1720–32. http://dx.doi.org/10.1139/f95-764.

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Pacific, Atlantic, and Mediterranean populations of the swordfish (Xiphias gladius) are currently considered as separate fisheries management units, and populations in different regions of the Atlantic are thought to constitute different stocks on the basis of recapture data. To test these hypotheses we sequenced hypervariable segments of the control region of mitochondrial DNA in 35 swordfish from three regions of the Atlantic, as well as in 8 and 7 individuals from the Pacific and Mediterranean regions, respectively. Sixty of the 81 variable sites were confined to a 280 base pair stretch in the left domain of the control region, indicating that this segment is a rich source of genetic markers. Thirty-three haplotypes were found that could be assigned to two clades differing by 3.8% on average, and that diverged approximately 550 000 years ago. Clade I haplotypes were ubiquitous, but haplotypes from clade II predominated in the Mediterranean, and thus likely originated there during Pleistocene marine regressions. Overall, we conclude that there is extensive mixing of swordfish within the Atlantic Ocean. Sister-group relationships of haplotypes from different oceans indicate historical gene flow between these populations, but the co-occurrence of the same haplotypes in different oceans must reflect recent or ongoing dispersal.

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Rus Hoelzel, A., Mahmood S. Shivji, Jennifer Magnussen et Malcolm P. Francis. « Low worldwide genetic diversity in the basking shark ( Cetorhinus maximus ) ». Biology Letters 2, n^o 4 (27 juin 2006) : 639–42. http://dx.doi.org/10.1098/rsbl.2006.0513.

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The basking shark ( Cetorhinus maximus ) is found in temperate waters throughout the world's oceans, and has been subjected to extensive exploitation in some regions. However, little is known about its current abundance and genetic status. Here, we investigate the diversity of the mitochondrial DNA control region among samples from the western North Atlantic, eastern North Atlantic, Mediterranean Sea, Indian Ocean and western Pacific. We find just six haplotypes defined by five variable sites, a comparatively low genetic diversity of π =0.0013 and no significant differentiation between ocean basins. We provide evidence for a bottleneck event within the Holocene, estimate an effective population size ( N e ) that is low for a globally distributed species, and discuss the implications.

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Pandey, Hemant Kumar, et Akhilesh Dwivedi. « STRATEGIC ROLE OF INDIAN NAVY IN IOR AT PRESENT ». SCHOLARLY RESEARCH JOURNAL FOR HUMANITY SCIENCE AND ENGLISH LANGUAGE 9, n^o 46 (25 mars 2021) : 11318–25. http://dx.doi.org/10.21922/srjhsel.v9i46.1541.

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The Indian Ocean Region (IOR) turned out to be the most engaging region for global activities in recent years. The Indian Ocean consists of the most important trade routes of the world. The Indian Ocean provides a way to move through various regions of the world. World's huge economic players always keep an eye on the IOR for its strategic importance. The Indian Ocean is a gateway to the Atlantic Ocean through the Mediterranean Sea via the Red Sea and it also provides a way to the Pacific Ocean through the Strait of Malacca. It is the main shipping channel for the Pacific and Atlantic oceans. The Indian Ocean region is spread over 28 states, three continents and covers 17.5% of the global land area. The IOR is home to almost 36% of the population of the world. The region is proven to have a rich petroleum resources and other metals. Indian Ocean is also a rich source of fish and its export. Major Sea routes of the world pass through the Indian Ocean that connects the Middle East, Africa, and East Asia with Europe and the Americas. The Indian Ocean Region (IOR) has become a home for economic developments, disputes, conflicts, and competition for regional influence by regional and extra-regional powers. The Trade flow from IOR across the globe has its importance for the global economy as well as regional countries. The growing presence of regional power (China) is a major concern for India and other regional countries and that has compelled them to reshape their maritime strategies. This article aims to state the importance of IOR in Indian reference and Chinese presence in IOR and its strategies.

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Bellomo, Katinka, Amy C. Clement, Thorsten Mauritsen, Gaby Rädel et Bjorn Stevens. « The Influence of Cloud Feedbacks on Equatorial Atlantic Variability ». Journal of Climate 28, n^o 7 (27 mars 2015) : 2725–44. http://dx.doi.org/10.1175/jcli-d-14-00495.1.

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Abstract Observations show that cloud feedback over the Namibian stratocumulus region is positive because cloud cover is anticorrelated with local sea surface temperature (SST) anomalies. Moreover, regressions of observed atmospheric fields on equatorial Atlantic SST anomalies indicate that cloud feedbacks over the Namibian stratocumulus region covary with Atlantic Niño. However, from observations alone, it is not possible to quantify the influence of regional cloud feedbacks on equatorial climate variability. To address this question, a set of sensitivity experiments are conducted using an atmospheric general circulation model (ECHAM6) coupled to a slab ocean in which the strength of positive cloud feedback is enhanced over several regions in the South Atlantic basin. Enhanced positive cloud feedback over the Namibian stratocumulus region increases local as well as equatorial SST variability, whereas enhanced cloud feedback over other regions in the South Atlantic increases local SST variability but exhibits negligible responses at the equator. The authors’ results indicate that the Namibian region plays a central role in enhancing equatorial SST variability because it is located where the SST anomalies associated with the simulated Atlantic Niño in the slab-ocean model develop. These results highlight the important role of the regional coupling of cloud cover over the Namibian region with local SSTs and its effects on equatorial Atlantic climate variability.

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Joshi, Manish K., Muhammad Adnan Abid et Fred Kucharski. « The Role of an Indian Ocean Heating Dipole in the ENSO Teleconnection to the North Atlantic European Region in Early Winter during the Twentieth Century in Reanalysis and CMIP5 Simulations ». Journal of Climate 34, n^o 3 (février 2021) : 1047–60. http://dx.doi.org/10.1175/jcli-d-20-0269.1.

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AbstractIn this study the role of an Indian Ocean heating dipole anomaly in the transition of the North Atlantic–European (NAE) circulation response to El Niño–Southern Oscillation (ENSO) from early to late winter is analyzed using a twentieth-century reanalysis and simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). It is shown that in early winter a warm (cold) ENSO event is connected through an atmospheric bridge with positive (negative) rainfall anomalies in the western Indian Ocean and negative (positive) anomalies in the eastern Indian Ocean. The early winter heating dipole, forced by a warm (cold) ENSO event, can set up a wave train emanating from the subtropical South Asian jet region that reaches the North Atlantic and leads to a response that spatially projects onto the positive (negative) phase of the North Atlantic Oscillation. The Indian Ocean heating dipole is partly forced as an atmospheric teleconnection by ENSO, but can also exist independently and is not strongly related to local Indian Ocean sea surface temperature (SST) forcing. The Indian Ocean heating dipole response to ENSO is much weaker in late winter (i.e., February and March) and not able to force significant signals in the North Atlantic region. CMIP5 multimodel ensemble reproduces the early winter Indian Ocean heating dipole response to ENSO and its transition in the North Atlantic region to some extent, but with weaker amplitude. Generally, models that have a strong early winter ENSO response in the subtropical South Asian jet region along with tropical Indian Ocean heating dipole also reproduce the North Atlantic response.

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Stocker, Thomas F., et Daniel G. Wright. « The Effect of a Succession of Ocean Ventilation Changes on 14C ». Radiocarbon 40, n^o 1 (1997) : 359–66. http://dx.doi.org/10.1017/s0033822200018233.

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Using the model of Stacker and Wright (1996), we investigate the effect of a succession of ocean ventilation changes on the atmospheric concentration of radiocarbon, δ14Catm, the surface reservoir ages, the top-to-bottom age differences, and the calendar-14C age relationships in different regions of the ocean. The model includes a representation of the cycling of 14C through the atmosphere, the ocean and the land biosphere. Ocean ventilation changes are triggered by increasing rates of freshwater discharge into the North Atlantic, which are determined according to a simple feedback mechanism between the melting rates and the climatic state of the North Atlantic region. The results demonstrate that ventilation changes can cause δ14Catm fluctuations of 25%, surface reservoir age fluctuations of 100 yr in the Pacific (200 yr in the Atlantic) and top-to-bottom age variations of 500 yr in the Pacific (1000 yr in the Atlantic). We also show that 14C age estimates based on marine organisms that live in the near-surface region of the ocean and take up the signal of surface 14C can result in apparent age reversals if the assumption of a constant reservoir age is made.

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Steinfeldt, R., T. Tanhua, J. L. Bullister, R. M. Key, M. Rhein et J. Köhler. « Atlantic CFC data in CARINA ». Earth System Science Data Discussions 2, n^o 1 (9 juillet 2009) : 27–61. http://dx.doi.org/10.5194/essdd-2-27-2009.

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Abstract. Water column data of carbon and carbon-relevant parameters have been collected and merged into a new database called CARINA (CARbon IN the Atlantic). In order to provide a consistent data set, all data have been examined for systematic biases and adjusted if necessary (secondary quality control (QC)). The CARINA data set is divided into three regions: the Arctic/Nordic Seas, the Atlantic region and the Southern Ocean. Here we present the CFC data for the Atlantic region, including the chlorofluorocarbons CFC-11, CFC-12 and CFC-113 as well as carbon tetrachloride (CCl4). The methods applied for the secondary quality control, a crossover analyses, the investigation of CFC ratios in the ocean and the CFC surface saturation are presented. Bases on the results, the CFC data of some cruises are adjusted by a certain factor or given a "poor" quality flag.

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Steinfeldt, R., T. Tanhua, J. L. Bullister, R. M. Key, M. Rhein et J. Köhler. « Atlantic CFC data in CARINA ». Earth System Science Data 2, n^o 1 (11 janvier 2010) : 1–15. http://dx.doi.org/10.5194/essd-2-1-2010.

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Abstract. Water column data of carbon and carbon-relevant parameters have been collected and merged into a new database called CARINA (CARbon IN the Atlantic). In order to provide a consistent data set, all data have been examined for systematic biases and adjusted if necessary (secondary quality control (QC)). The CARINA data set is divided into three regions: the Arctic/Nordic Seas, the Atlantic region and the Southern Ocean. Here we present the CFC data for the Atlantic region, including the chlorofluorocarbons CFC-11, CFC-12 and CFC-113 as well as carbon tetrachloride (CCl4). The methods applied for the secondary quality control, a crossover analyses, the investigation of CFC ratios in the ocean and the CFC surface saturation are presented. Based on the results, the CFC data of some cruises are adjusted by a certain factor or given a "poor'' quality flag.

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Dey, Dipanjan, Aitor Aldama Campino et Kristofer Döös. « Atmospheric water transport connectivity within and between ocean basins and land ». Hydrology and Earth System Sciences 27, n^o 2 (24 janvier 2023) : 481–93. http://dx.doi.org/10.5194/hess-27-481-2023.

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Abstract. The global atmospheric water transport from the net evaporation to the net precipitation regions has been traced using Lagrangian trajectories. A matrix has been constructed by selecting various group of trajectories based on their surface starting (net evaporation) and ending (net precipitation) positions to show the connectivity of the 3-D atmospheric water transport within and between the three major ocean basins and the global landmass. The analysis reveals that a major portion of the net evaporated water precipitates back into the same region, namely 67 % for the Indian Ocean, 64 % for the Atlantic Ocean, 85 % for the Pacific Ocean and 72 % for the global landmass. It has also been calculated that 58 % of the net terrestrial precipitation was sourced from land evaporation. The net evaporation from the subtropical regions of the Indian, Atlantic and Pacific oceans is found to be the primary source of atmospheric water for precipitation over the Intertropical Convergence Zone (ITCZ) in the corresponding basins. The net evaporated waters from the subtropical and western Indian Ocean were traced as the source for precipitation over the South Asian and eastern African landmass, while Atlantic Ocean waters are responsible for rainfall over North Asia and western Africa. Atlantic storm tracks were identified as the carrier of atmospheric water that precipitates over Europe, while the Pacific storm tracks were responsible for North American, eastern Asian and Australian precipitation. The bulk of South and Central American precipitation is found to have its source in the tropical Atlantic Ocean. The land-to-land atmospheric water transport is pronounced over the Amazon basin, western coast of South America, Congo basin, northeastern Asia, Canada and Greenland. The ocean-to-land and land-to-ocean water transport through the atmosphere was computed to be 2×109 and 1×109 kg s−1, respectively. The difference between them (net ocean-to-land transport), i.e. 1×109 kg s−1, is transported to land. This net transport is approximately the same as found in previous estimates which were calculated from the global surface water budget.

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Borchert, Leonard F., Wolfgang A. Müller et Johanna Baehr. « Atlantic Ocean Heat Transport Influences Interannual-to-Decadal Surface Temperature Predictability in the North Atlantic Region ». Journal of Climate 31, n^o 17 (septembre 2018) : 6763–82. http://dx.doi.org/10.1175/jcli-d-17-0734.1.

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An analysis of a three-member ensemble of initialized coupled simulations with the MPI-ESM-LR covering the period 1901–2010 shows that Atlantic northward ocean heat transport (OHT) at 50°N influences surface temperature variability in the North Atlantic region for several years. Three to ten years after strong OHT phases at 50°N, a characteristic pattern of sea surface temperature (SST) anomalies emerges: warm anomalies are found in the North Atlantic and cold anomalies emerge in the Gulf Stream region. This pattern originates from persistent upper-ocean heat content anomalies that originate from southward-propagating OHT anomalies in the North Atlantic. Interannual-to-decadal SST predictability of yearly initialized hindcasts is linked to this SST pattern: when ocean heat transport at 50°N is strong at the initialization of a hindcast, SST anomaly correlation coefficients in the northeast Atlantic at lead years 2–9 are significantly higher than when the ocean heat transport at 50°N is weak at initialization. Surface heat fluxes that mask the predictable low-frequency oceanic variability that influences SSTs in the northwest Atlantic after strong OHT phases, and in the northwest and northeast Atlantic after weak OHT phases at 50°N lead to zonally asymmetrically predictable SSTs 7–9 years ahead. This study shows that the interannual-to-decadal predictability of North Atlantic SSTs depends strongly on the strength of subpolar ocean heat transport at the start of a prediction, indicating that physical mechanisms need to be taken into account for actual temperature predictions.

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Muñoz, Ernesto, Wilbert Weijer, Semyon A. Grodsky, Susan C. Bates et Ilana Wainer. « Mean and Variability of the Tropical Atlantic Ocean in the CCSM4* ». Journal of Climate 25, n^o 14 (15 juillet 2012) : 4860–82. http://dx.doi.org/10.1175/jcli-d-11-00294.1.

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Abstract This study analyzes important aspects of the tropical Atlantic Ocean from simulations of the fourth version of the Community Climate System Model (CCSM4): the mean sea surface temperature (SST) and wind stress, the Atlantic warm pools, the principal modes of SST variability, and the heat budget in the Benguela region. The main goal was to assess the similarities and differences between the CCSM4 simulations and observations. The results indicate that the tropical Atlantic overall is realistic in CCSM4. However, there are still significant biases in the CCSM4 Atlantic SSTs, with a colder tropical North Atlantic and a hotter tropical South Atlantic, that are related to biases in the wind stress. These are also reflected in the Atlantic warm pools in April and September, with its volume greater than in observations in April and smaller than in observations in September. The variability of SSTs in the tropical Atlantic is well represented in CCSM4. However, in the equatorial and tropical South Atlantic regions, CCSM4 has two distinct modes of variability, in contrast to observed behavior. A model heat budget analysis of the Benguela region indicates that the variability of the upper-ocean temperature is dominated by vertical advection, followed by meridional advection.

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Zhao, Ping, Song Yang, Renguang Wu, Zhiping Wen, Junming Chen et Huijun Wang. « Asian Origin of Interannual Variations of Summer Climate over the Extratropical North Atlantic Ocean ». Journal of Climate 25, n^o 19 (11 avril 2012) : 6594–609. http://dx.doi.org/10.1175/jcli-d-11-00617.1.

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Abstract The authors have identified an interannual relationship between Asian tropospheric temperature and the North Atlantic Ocean sea surface temperature (SST) during summer (May–September) and discussed the associated features of atmospheric circulation over the Atlantic–Eurasian region. When tropospheric temperature is high (low) over Asia, positive (negative) SST anomalies appear in the extratropical North Atlantic. This relationship is well supported by the changes in background atmospheric circulation and ocean–atmosphere–land thermodynamic processes. When heat transfer from the land surface to the atmosphere over Asia strengthens, local tropospheric temperature increases and positive temperature anomalies propagate westward from Asia to the North Atlantic, leading to an increase in summer tropospheric temperature over the Atlantic–Eurasian region. Accordingly, a deep anomalous ridge occurs over the extratropical North Atlantic Ocean, with low-level southerly anomalies over the western portion of the ocean. Sensitivity experiments with climate models show that the interannual variations of the North Atlantic–Eurasian atmospheric circulation may not be forced by the extratropical Atlantic SST. Instead, experiments with changing Asian land surface heating capture the above observed features of atmospheric circulation anomalies, westward propagation of tropospheric anomalies, and Atlantic SST anomalies. The consistency between the observational and model results indicates a possible impact of Asian land heating on the development of atmospheric circulation and SST anomalies over the Atlantic–Eurasian region.

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Pérez-Alarcón, Albenis, Rogert Sorí, José Carlos Fernández-Alvarez, Raquel Nieto et Luis Gimeno. « Moisture Sources for Tropical Cyclones Genesis in the Coast of West Africa through a Lagrangian Approach ». Environmental Sciences Proceedings 4, n^o 1 (13 novembre 2020) : 3. http://dx.doi.org/10.3390/ecas2020-08126.

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Atmospheric moisture transport plays an important role in the genesis of tropical cyclones (TCs). In this study, the moisture sources associated with the genesis of TCs in the tropical Atlantic Ocean near West Africa, from June to November in the period 1980–2018, were identified. To detect the location of the TCs geneses, the HURDAT2 database from the National Hurricane Center was used. Additionally, global outputs of the Lagrangian FLEXPART model were used to determine the moisture sources that provided water vapor for the genesis of TCs. This model permitted us to track backward in time the air masses from the genesis region of the TCs and identify regions where air masses uptake moisture before reach the target regions. The results reveal that 18.1% (108 TC) of the total number of TCs that formed in the North Atlantic basin were originated in the region of study. The largest frequency for the TCs geneses was observed in August and September, with each one representing approximately 45% of the total. The transport of moisture associated with the genesis of TCs mainly comes from the east of the North and South Atlantic Ocean, as well as from West Africa and the Sahel region. The patterns of moisture uptake confirmed an interhemispheric moisture transport. Finally, during the El Niño, the moisture uptake is more intense over the Atlantic Ocean close to West Africa around 15 °N of latitude, while during La Niña, the pattern is slightly weaker but covers a wider area over the Atlantic Ocean and the north of Africa.

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Kadiri, Medina Omo, et Osasere Abike Omoruyi. « Dynamics of Odontella spp. in the Atlantic Ocean of Nigeria ». Nova Hedwigia 110, n^o 3 (1 mai 2020) : 227–46. http://dx.doi.org/10.1127/nova_hedwigia/2020/0578.

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Odontella is a planktonic centric diatom widely distributed in saline waters. Although some studies on marine phytoplankton in Nigeria mention the genus, there is a considerable dearth of information on its distribution in the Atlantic Ocean (Nigeria). This paper examined the density, diversity, spatial and temporal distribution of Odontella species in the Atlantic Ocean, in the Bight of Benin and Bight of Bonny (Nigeria). Phytoplankton samples were collected from 10 locations on the stretch of the Atlantic Ocean (Nigeria), in four seasons (dry-wet, wet, wet-dry and dry). Results revealed that eight species of Odontella, namely O. aurita, O. granulata, O. longicruris, O. mobilensis, O. obtusa, O. regia, O. rhombus and O. sinensis occurred in the Atlantic Ocean (Nigeria). The eight Odontella species showed differential distributional pattern, both spatially and temporally. Akwa Ibom location had the highest Odontella abundance in the South-South region while Ondo was highest in the South-West region. Higher Odontella abundance was recorded in the transition seasons (dry-wet and wet-dry seasons) than in the typically wet and dry seasons. The species O. regia was dominant and widely distributed in the South-West region, while O. aurita was dominant in the South-South region. Relatively, the density of O. longicruris was low throughout the Atlantic Ocean (Nigeria) and at all seasons. O. regia and O. sinensis were the most widely distributed species in the Atlantic Ocean (Nigeria) and occurred all through the seasons studied while O. obtusa occurred sparingly throughout all the seasons.

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Karstensen, J., B. Fiedler, F. Schütte, P. Brandt, A. Körtzinger, G. Fischer, R. Zantopp, J. Hahn, M. Visbeck et D. Wallace. « Open ocean dead-zone in the tropical North Atlantic Ocean ». Biogeosciences Discussions 11, n^o 12 (12 décembre 2014) : 17391–411. http://dx.doi.org/10.5194/bgd-11-17391-2014.

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Abstract. The intermittent appearances of low oxygen environments are a particular thread for marine ecosystems. Here we present first observations of unexpected low (<2 μmol kg-1) oxygen environments in the open waters of the eastern tropical North Atlantic, a region where typically oxygen concentration does not fall below 40 μmol kg-1. The low oxygen zones are created just below the mixed-layer, in the euphotic zone of high productive cyclonic and anticyclonic-modewater eddies. A dynamic boundary is created from the large swirl-velocity against the weak background flow. Hydrographic properties within the eddies are kept constant over periods of several months, while net respiration is elevated by a factor of 3 to 5 reducing the oxygen content. We repeatedly observed low oxygen eddies in the region. The direct impact on the ecosystem is evident from anomalous backscatter behaviour. Satellite derived global eddy statistics do not allow to estimate the large-scale impact of the eddies because their vertical structure (mixed-layer depth, euphotic depth) play a key role in creating the low oxygen environment.

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Wu, Qiaoyan, et Yilei Wang. « Comparison of Oceanic Multisatellite Precipitation Data from Tropical Rainfall Measurement Mission and Global Precipitation Measurement Mission Datasets with Rain Gauge Data from Ocean Buoys ». Journal of Atmospheric and Oceanic Technology 36, n^o 5 (mai 2019) : 903–20. http://dx.doi.org/10.1175/jtech-d-18-0152.1.

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AbstractThree satellite-derived precipitation datasets [the Tropical Rainfall Measuring Mission Multisatellite Precipitation Analysis (TMPA) dataset, the NOAA Climate Prediction Center morphing technique (CMORPH) dataset, and the newly available Integrated Multisatellite Retrievals for Global Precipitation Measurement (IMERG) dataset] are compared with data obtained from 55 rain gauges mounted on floating buoys in the tropics for the period 1 April 2014–30 April 2017. All three satellite datasets underestimate low rainfall and overestimate high rainfall in the tropical Pacific Ocean, but the TMPA dataset does this the most. In the high-rainfall (higher than 4 mm day−1) Atlantic region, all three satellite datasets overestimate low rainfall and underestimate high rainfall, but the IMERG dataset does this the most. For the Indian Ocean, all three rainfall satellite datasets overestimate rainfall at some gauges and underestimate it at others. Of these three satellite products, IMERG is the most accurate in estimating mean precipitation over the tropical Pacific and Indian Oceans, but it is less accurate over the tropical Atlantic Ocean for regions of high rainfall. The differences between the three satellite datasets vary by region and there is a need to consider uncertainties in the data before using them for research.

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Kuijpers, Antoon, Jørn Bo Jensen, Simon R. Troelstra et And shipboard scientific party of RV Professor Logachev and RV Dana. « Late Quaternary palaeo-oceanography of the Denmark Strait overflow pathway, South-East Greenland margin ». Geology of Greenland Survey Bulletin 180 (31 décembre 1998) : 163–67. http://dx.doi.org/10.34194/ggu-bulletin.v180.6514.

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Direct interaction between the atmosphere and the deep ocean basins takes place today only in the Southern Ocean near the Antarctic continent and in the northern extremity of the North Atlantic Ocean, notably in the Norwegian–Greenland Sea and Labrador Sea. Cooling and evaporation cause surface waters in the latter region to become dense and sink. At depth, further mixing occurs with Arctic water masses from adjacent polar shelves. Export of these water masses from the Norwegian–Greenland Sea (Norwegian Sea Overflow Water) to the North Atlantic basin occurs via two major gateways, the Denmark Strait system and the Faeroe– Shetland Channel and Faeroe Bank Channel system (e.g. Dickson et al. 1990; Fig.1). Deep convection in the Labrador Sea produces intermediate waters (Labrador Sea Water), which spreads across the North Atlantic. Deep waters thus formed in the North Atlantic (North Atlantic Deep Water) constitute an essential component of a global ‘conveyor’ belt extending from the North Atlantic via the Southern and Indian Oceans to the Pacific. Water masses return as a (warm) surface water flow. In the North Atlantic this is the Gulf Stream and the relatively warm and saline North Atlantic Current. Numerous palaeo-oceanographic studies have indicated that climatic changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic Deep Water. Abrupt shut-down of the ocean-overturning and subsequently of the conveyor belt is believed to represent a potential explanation for rapid climate deterioration at high latitudes, such as those that caused the Quaternary ice ages. Here it should be noted, that significant changes in deep convection in Greenland waters have also recently occurred. While in the Greenland Sea deep water formation over the last decade has drastically decreased, a strong increase of deep convection has simultaneously been observed in the Labrador Sea (Sy et al. 1997).

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Kuijpers, Antoon, Jørn Bo Jensen, Simon R. Troelstra et And shipboard scientific party of RV Professor Logachev and RV Dana. « Late Quaternary palaeo-oceanography of the Denmark Strait overflow pathway, South-East Greenland margin ». Geology of Greenland Survey Bulletin 180 (31 décembre 1998) : 163–67. http://dx.doi.org/10.34194/ggub.v180.6514.

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Direct interaction between the atmosphere and the deep ocean basins takes place today only in the Southern Ocean near the Antarctic continent and in the northern extremity of the North Atlantic Ocean, notably in the Norwegian–Greenland Sea and Labrador Sea. Cooling and evaporation cause surface waters in the latter region to become dense and sink. At depth, further mixing occurs with Arctic water masses from adjacent polar shelves. Export of these water masses from the Norwegian–Greenland Sea (Norwegian Sea Overflow Water) to the North Atlantic basin occurs via two major gateways, the Denmark Strait system and the Faeroe– Shetland Channel and Faeroe Bank Channel system (e.g. Dickson et al. 1990; Fig.1). Deep convection in the Labrador Sea produces intermediate waters (Labrador Sea Water), which spreads across the North Atlantic. Deep waters thus formed in the North Atlantic (North Atlantic Deep Water) constitute an essential component of a global ‘conveyor’ belt extending from the North Atlantic via the Southern and Indian Oceans to the Pacific. Water masses return as a (warm) surface water flow. In the North Atlantic this is the Gulf Stream and the relatively warm and saline North Atlantic Current. Numerous palaeo-oceanographic studies have indicated that climatic changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic Deep Water. Abrupt shut-down of the ocean-overturning and subsequently of the conveyor belt is believed to represent a potential explanation for rapid climate deterioration at high latitudes, such as those that caused the Quaternary ice ages. Here it should be noted, that significant changes in deep convection in Greenland waters have also recently occurred. While in the Greenland Sea deep water formation over the last decade has drastically decreased, a strong increase of deep convection has simultaneously been observed in the Labrador Sea (Sy et al. 1997).

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Tanhua, T., R. Steinfeldt, R. M. Key, P. Brown, N. Gruber, R. Wanninkhof, F. Perez et al. « Atlantic Ocean CARINA data : overview and salinity adjustments ». Earth System Science Data Discussions 2, n^o 1 (20 août 2009) : 241–80. http://dx.doi.org/10.5194/essdd-2-241-2009.

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Abstract. Water column data of carbon and carbon-relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruise data sets in the Arctic, Atlantic and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon IN the Atlantic). The data have gone through rigorous quality control procedures to assure the highest possible quality and consistency. The data for the pertinent parameters in the CARINA database were objectively examined in order to quantify systematic differences in the reported values, i.e. secondary quality control. Systematic biases found in the data have been corrected in the data products, i.e. three merged data files with measured, calculated and interpolated data for each of the three CARINA regions, i.e. Arctic, Atlantic and Southern Ocean. Ninety-eight of the cruises in the CARINA database were conducted in the Atlantic Ocean, defined here as the region south of the Greenland-Iceland-Scotland Ridge and north of about 30° S. Here we present an overview of the Atlantic Ocean synthesis of the CARINA data and the adjustments that were applied to the data product. We also report details of the secondary QC for salinity for this data set. Procedures of quality control – including crossover analysis between stations and inversion analysis of all crossover data – are briefly described. Adjustments to salinity measurements were applied to the data from 10 cruises in the Atlantic Ocean region. Based on our analysis we estimate the internal accuracy of the CARINA-ATL salinity data to be 4.1 ppm. With these adjustments the CARINA database is consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s (Key et al., 2004), and is now suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation.

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Kisesa, Makula, Marie Umutoni, Lovina Japheth, Elias Lipiki, Laban Kebacho et Shelleph Tilwebwa. « The covariability of sea surface temperature and MAM rainfall on East Africa using singular value decomposition analysis ». Geographica Pannonica 24, n^o 4 (2020) : 261–70. http://dx.doi.org/10.5937/gp24-27577.

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The study assesses the covariability of Sea Surface Temperature (SST) and March to May (MAM) rainfall variability on East Africa (EA) from 1981 to 2018. Singular Value Decomposition (SVD) analysis reveals the significant influence of SST anomalies on MAM rainfall, with covariability of 91%, 88.61%, and 82.9% for Indian, Atlantic, and the Pacific Ocean, respectively. The Indian Ocean explains the variability of rainfall to the large extent followed by the Atlantic Ocean and the Pacific Ocean. The rainfall patterns over the EA correspond to SST variability over the western, central, and Eastern Indian Ocean. Likewise, the variability of SST anomalies was observed over the central, south, and North of the Atlantic Ocean while the Pacific Ocean captured the El Nino Modoki (ENSO) like pattern in the SVD1 (SVD2). The heterogeneous correlation of Indian SST anomalies and rainfall over EA of the first (second) principal component (PC) shows a positive correlation over much of the domain (central region). The SST anomalies over the Pacific Ocean show higher correlation values with the rainfall over much of the study domain except over the southwestern highland and southern region of Tanzania. Over the Atlantic Ocean, the correlation result shows the patterns of positive (negative) values over the northern (southern) part for PC1, while PC2 depicts negative correlation values over much of the Ocean. SST anomalies over the Indian (Atlantic) Ocean are highly correlated with MAM rainfall when SST leads by 1(7) month(s). The Pacific Ocean shows a weak (strong) correlation across all (zero) lead seasons.

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Sokov, A. V. « TO THE 80th ANNIVERSARY OF BYSHEV – A MEMBER OF THE POLYGON–70 EXPEDITION ». Journal of Oceanological Research 48, n^o 3 (30 octobre 2020) : 236–43. http://dx.doi.org/10.29006/1564-2291.jor-2020.48(3).14.

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The article is dedicated to the 80th anniversary of Dr. Vladimir I. Byshev – mathematician, oceanologist, Head of the Laboratory of large-scale variability of hydrophysical fields of the Shirshov Institute of Oceanology of Russian Academy of Sciences. Vladimir Byshev is a major scientist in the study of the temporal and spatial variability of oceanological and meteorological characteristics in a wide range of scales, features of the interaction of the ocean and atmosphere, large-scale disturbances of the climate system, an active direct participant in two dozen scientific expeditions, including such large ocean projects as Polygon–70, POLYMODE, Megapolygon, Atlantex–90, as well as a number of expeditions to the regions of the western boundary currents of the Atlantic Ocean and the equatorial region of the Indian Ocean, in which new, previously unknown elements of the circulation of the World Ocean were discovered. He is an expert in the field of climate, a member of the Editorial boards of several scientific journals and the author of over 200 scientific publications. He is a co-author of the Atlas POLYMODE (1986), the largest international oceans research project, and the author of the well-known monograph “Synoptic and large-scale variability of the ocean and atmosphere”.

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Meccia, Virna L., Doroteaciro Iovino et Alessio Bellucci. « North Atlantic gyre circulation in PRIMAVERA models ». Climate Dynamics 56, n^o 11-12 (14 février 2021) : 4075–90. http://dx.doi.org/10.1007/s00382-021-05686-z.

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AbstractWe study the impact of horizontal resolution in setting the North Atlantic gyre circulation and representing the ocean–atmosphere interactions that modulate the low-frequency variability in the region. Simulations from five state-of-the-art climate models performed at standard and high-resolution as part of the High-Resolution Model Inter-comparison Project (HighResMIP) were analysed. In some models, the resolution is enhanced in the atmospheric and oceanic components whereas, in some other models, the resolution is increased only in the atmosphere. Enhancing the horizontal resolution from non-eddy to eddy-permitting ocean produces stronger barotropic mass transports inside the subpolar and subtropical gyres. The first mode of inter-annual variability is associated with the North Atlantic Oscillation (NAO) in all the cases. The rapid ocean response to it consists of a shift in the position of the inter-gyre zone and it is better captured by the non-eddy models. The delayed ocean response consists of an intensification of the subpolar gyre (SPG) after around 3 years of a positive phase of NAO and it is better represented by the eddy-permitting oceans. A lagged relationship between the intensity of the SPG and the Atlantic Meridional Overturning Circulation (AMOC) is stronger in the cases of the non-eddy ocean. Then, the SPG is more tightly coupled to the AMOC in low-resolution models.

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Cessi, Paola. « The Effect of Northern Hemisphere Winds on the Meridional Overturning Circulation and Stratification ». Journal of Physical Oceanography 48, n^o 10 (octobre 2018) : 2495–506. http://dx.doi.org/10.1175/jpo-d-18-0085.1.

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AbstractThe current paradigm for the meridional overturning cell and the associated middepth stratification is that the wind stress in the subpolar region of the Southern Ocean drives a northward Ekman flow, which, together with the global diapycnal mixing across the lower boundary of the middepth waters, feeds the upper branch of the interhemispheric overturning. The resulting mass transport proceeds to the Northern Hemisphere of the North Atlantic, where it sinks, to be eventually returned to the Southern Ocean at depth. Seemingly, the wind stress in the Atlantic basin plays no role. This asymmetry occurs because the Ekman transport in the Atlantic Ocean is assumed to return geostrophically at depths much shallower than those occupied by the interhemispheric overturning. However, this vertical separation fails in the North Atlantic subpolar gyre region. Using a conceptual model and an ocean general circulation model in an idealized geometry, we show that the westerly wind stress in the northern part of the Atlantic provides two opposing effects. Mechanically, the return of the Ekman transport in the North Atlantic opposes sinking in this region, reducing the total overturning and deepening the middepth stratification; thermodynamically, the subpolar gyre advects salt poleward, promoting Northern Hemisphere sinking. Depending on which mechanism prevails, increased westerly winds in the Northern Hemisphere can reduce or augment the overturning.

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Zhai, Xiaoming, et Luke Sheldon. « On the North Atlantic Ocean Heat Content Change between 1955–70 and 1980–95 ». Journal of Climate 25, n^o 10 (14 mai 2012) : 3619–28. http://dx.doi.org/10.1175/jcli-d-11-00187.1.

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Abstract The upper-ocean heat content of the North Atlantic has undergone significant changes over the last 50 years but the underlying physical mechanisms are not yet well understood. In the present study, the authors examine the North Atlantic ocean heat content change in the upper 700 m between the 1955–70 and 1980–95 periods. Consistent with previous studies, the large-scale pattern consists of warming of the tropics and subtropics and cooling of the subpolar ocean. However, this study finds that the most significant heat content change in the North Atlantic during these two time periods is the warming of the Gulf Stream region. Numerical experiments strongly suggest that this warming in the Gulf Stream region is largely driven by changes of the large-scale wind forcing. Furthermore, the increased ocean heat content in the Gulf Stream region appears to feedback on to the atmosphere, resulting in warmer surface air temperature and enhanced precipitation there.

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Tanhua, T., R. Steinfeldt, R. M. Key, P. Brown, N. Gruber, R. Wanninkhof, F. Perez et al. « Atlantic Ocean CARINA data : overview and salinity adjustments ». Earth System Science Data 2, n^o 1 (1 février 2010) : 17–34. http://dx.doi.org/10.5194/essd-2-17-2010.

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Abstract. Water column data of carbon and carbon-relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruise data sets in the Arctic Mediterranean Seas, Atlantic and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon dioxide IN the Atlantic Ocean). The data have gone through rigorous quality control procedures to assure the highest possible quality and consistency. The data for the pertinent parameters in the CARINA database were objectively examined in order to quantify systematic differences in the reported values, i.e. secondary quality control. Systematic biases found in the data have been corrected in the three data products: merged data files with measured, calculated and interpolated data for each of the three CARINA regions, i.e. the Arctic Mediterranean Seas, the Atlantic and the Southern Ocean. These products have been corrected to be internally consistent. Ninety-eight of the cruises in the CARINA database were conducted in the Atlantic Ocean, defined here as the region south of the Greenland-Iceland-Scotland Ridge and north of about 30° S. Here we present an overview of the Atlantic Ocean synthesis of the CARINA data and the adjustments that were applied to the data product. We also report the details of the secondary QC (Quality Control) for salinity for this data set. Procedures of quality control – including crossover analysis between stations and inversion analysis of all crossover data – are briefly described. Adjustments to salinity measurements were applied to the data from 10 cruises in the Atlantic Ocean region. Based on our analysis we estimate the internal consistency of the CARINA-ATL salinity data to be 4.1 ppm. With these adjustments the CARINA data products are consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s, and is now suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation.

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Karstensen, J., B. Fiedler, F. Schütte, P. Brandt, A. Körtzinger, G. Fischer, R. Zantopp, J. Hahn, M. Visbeck et D. Wallace. « Open ocean dead zones in the tropical North Atlantic Ocean ». Biogeosciences 12, n^o 8 (30 avril 2015) : 2597–605. http://dx.doi.org/10.5194/bg-12-2597-2015.

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Abstract. Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day−1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies.

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Siqueira, Beatriz, Jonas Teixeira Nery et Oliver Messeguer-Ruiz. « Análise dos Índices das Temperaturas Superficiais das Zonas Intertropicais dos Oceanos Pacífico e Atlântico associados às precipitações no Nordeste do Brasil ». Revista Brasileira de Geografia Física 14, n^o 2 (20 mai 2021) : 1081. http://dx.doi.org/10.26848/rbgf.v14.2.p1081-1093.

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O objetivo deste estudo foi analisar, através de índices climáticos, a variabilidade da precipitação na região Nordeste do Brasil. Para tanto foram utilizados dados em ponto de grade para gerar o índice de precipitação, bem como dados da National Oceanic Atmospheric Administration (NOAA) para gerar os índices de temperatura do oceano Pacífico (setor EN3.4) e do oceano Atlântico tropical norte e sul. O período de análise foi de 1970 a 2012. Com base nesses índices foram realizadas correlações lineares de Pearson, entre o oceano Pacífico e o Atlântico tropical norte e o oceano tropical sul, na costa do Brasil. Anomalias de precipitação também foram calculadas para alguns anos de ocorrência do evento El Niño, denotando expressiva variabilidade de um evento para outro. De maneira geral, as correlações entre os índices envolvendo os referidos oceanos foram positivas e expressivas, o que permite considerar a influência dos oceanos na dinâmica das chuvas na área de estudo. A importância do Atlântico sul é mais nítida quando os índices de temperatura da superfície do mar apresentaram o mesmo sinal, tanto no Pacífico quanto no Atlântico, o que implica em correlações mais marcadas.Palavras-chave: Forçante climática, El Niño 3.4, Nordeste do Brasil, Atlântico tropical, Anomalias da precipitação.Analysis of Surface Temperature Indices of the Intertropical Zones of the Pacific and Atlantic Oceans associated with rainfall in Northeastern Brazil ABSTRACTThe objective of this study was to analyze, through climatic indices, the variability of precipitation in the Northeast region of Brazil. For that purpose, grid point data were used characterize the precipitation behaviour, as well as data from the National Oceanic Atmospheric Administration (NOAA) to determine the temperature of the Pacific Ocean (sector EN3.4) and the tropical North and South Atlantic Ocean. Based on these data, correlations were made, which are characterized as marked, between the dynamics of the Pacific Ocean and the dynamics of the tropical North and South Atlantic, directly influencing the precipitation regime in Northeast Brazil. Precipitation anomalies were also calculated for some years of the El Niño event, showing significant variability from one event to another. In general, the correlations between the indexes involving the referred oceans were positive and expressive, which allows considering the influence of the oceans on the dynamics of rainfall in the study area. The importance of the South Atlantic is clearer when the sea surface temperature indices show the same sign, both in the Pacific and in the Atlantic, which implies more marked correlations.Keywords: Climate forcing, El Niño 3.4, Northeast Brazil, Tropical Atlantic, Precipitation anomalies.

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Watt, W. S., L. M. Larsen et M. Watt. « Volcanic history of the Lower Tertiary plateau basalts in the Scoresby Sund region, East Greenland ». Rapport Grønlands Geologiske Undersøgelse 128 (31 décembre 1986) : 147–56. http://dx.doi.org/10.34194/rapggu.v128.7931.

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The extensive plateau basalt lava pile in the Scoresby Sund region has a stratigraphic thickness of 3200 m and an overall average thickness of 1500 m. The pile thins inland from the Atlantic coast and laps onto basement gneisses and Jurassic sediments in the inner fjord region. The lavas are divisible into five formations which form two separate lava sequences. The lower sequence is best developed in the inner fjord region, while the upper sequence dominates the regions near the Atlantic coast. The sequences are interpreted as produced in two vo\canic episodes in connection with failed rifting episodes during the opening of the North Atlantic Ocean. At the Atlantic coast remains of a third separate lava sequence apparently forrned during active spreading.

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Sonnewald, M., J. J. M. Hirschi, R. Marsh, E. L. McDonagh et B. A. King. « Atlantic meridional ocean heat transport at 26° N : impact on subtropical ocean heat content variability ». Ocean Science 9, n^o 6 (5 décembre 2013) : 1057–69. http://dx.doi.org/10.5194/os-9-1057-2013.

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Abstract. Local climate is significantly affected by changes in the oceanic heat content on a range of timescales. This variability is driven by heat fluxes from both the atmosphere and the ocean. In the Atlantic the meridional overturning circulation is the main contributor to the oceanic meridional heat transport for latitudes south of about 50° N. The RAPID project has been successfully monitoring the Atlantic meridional overturning at 26° N since 2004. This study demonstrates how these data can be used to estimate the variability of the basin-wide ocean heat content in the upper 800 m between 26° and 36° N. Traditionally the atmosphere is seen to dominate the ocean heat content variability. However, previous studies have looked at smaller areas in the Gulf Stream region, finding that the ocean dominates deseasoned fluctuations of ocean heat content, while studies of the whole North Atlantic region suggest that the atmosphere may be dominant. In our study we use a box model to investigate fluctuations of the ocean heat content in the subtropical North Atlantic between 26° and 36° N. The box model approach is validated using 19 yr of high-resolution general circulation model (GCM) data. We find that in both the GCM- and RAPID-based data the ocean heat transport dominates the deseasoned heat content variability, while the atmosphere's impact on the ocean heat content evolution stabilizes after 6 months. We demonstrate that the utility of the RAPID data goes beyond monitoring the overturning circulation at 26° N, and that it can be used to better understand the causes of ocean heat content variability in the North Atlantic. We illustrate this for a recent decrease in ocean heat content which was observed in the North Atlantic in 2009 and 2010. Our results suggest that most of this ocean heat content reduction can be explained by a reduction of the meridional ocean heat transport during this period.

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Li, Laifang, M. Susan Lozier et Martha W. Buckley. « An Investigation of the Ocean’s Role in Atlantic Multidecadal Variability ». Journal of Climate 33, n^o 8 (15 avril 2020) : 3019–35. http://dx.doi.org/10.1175/jcli-d-19-0236.1.

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AbstractA mechanistic understanding of the Atlantic multidecadal variability (AMV) is highly desirable since it will considerably aid regional and global climate predictions. Although ocean dynamics have long been invoked to explain the AMV, recent studies have cast doubt on its influence. Here we evaluate the necessity of ocean dynamics for the AMV using an observationally based idealized model that isolates the contribution of atmospheric forcing to the AMV. By demonstrating that this model underestimates the magnitude of the observed sea surface temperature variability in the extratropical North Atlantic, we infer that ocean dynamics contribute significantly to the AMV in this region. This inference holds when we add anthropogenic aerosol forcing and the effects of mixed layer depth variability to the idealized model. Thus, our study suggests that ocean heat transport convergence is needed to explain sea surface temperature variability in the extratropical North Atlantic. Sustained ocean observing systems in the this region will help untangle the physical mechanisms involved.

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Yasuhara, Moriaki, Thomas M. Cronin, Gene Hunt et David A. Hodell. « Deep-sea ostracods from the South Atlantic sector of the Southern Ocean during the last 370,000 years ». Journal of Paleontology 83, n^o 6 (novembre 2009) : 914–30. http://dx.doi.org/10.1666/08-149.1.

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We report changes of deep-sea ostracod fauna during the last 370,000 yr from the Ocean Drilling Program (ODP) Hole 704A in the South Atlantic sector of the Southern Ocean. The results show that faunal changes are coincident with glacial/interglacial-scale deep-water circulation changes, even though our dataset is relatively small and the waters are barren of ostracods until mid-MIS (Marine Isotope Stage) 5.KritheandPoseidonamicuswere dominant during the Holocene interglacial period and the latter part of MIS 5, when this site was under the influence of North Atlantic Deep Water (NADW). Conversely,HenryhowellaandLegitimocytherewere dominant during glacial periods, when this site was in the path of Circumpolar Deep Water (CPDW). Three new species (Aversovalva brandaoae, Poseidonamicus hisayoae, andKrithe mazziniae) are described herein. This is the first report of Quaternary glacial/interglacial scale deep-sea ostracod faunal changes in the Southern and South Atlantic Oceans, a key region for understanding Quaternary climate and deep-water circulation, although the paucity of Quaternary ostracods in this region necessitates further research.

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Hu, Zeng-Zhen, et Bohua Huang. « The Predictive Skill and the Most Predictable Pattern in the Tropical Atlantic : The Effect of ENSO ». Monthly Weather Review 135, n^o 5 (1 mai 2007) : 1786–806. http://dx.doi.org/10.1175/mwr3393.1.

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Abstract This work investigates the predictive skill and most predictable pattern in the NCEP Climate Forecast System (CFS) in the tropical Atlantic Ocean. The skill is measured by the sea surface temperature (SST) anomaly correlation between the predictions and the corresponding analyses, and the most predictable patterns are isolated by an empirical orthogonal function analysis with a maximized signal-to-noise ratio. On average, for predictions with initial conditions (ICs) of all months, the predictability of SST is higher in the west than in the east. The highest skill is near the tropical Brazilian coast and in the Caribbean Sea, and the lowest skill occurs in the eastern coast. Seasonally, the skill is higher for predictions with ICs in summer or autumn and lower for those with ICs in spring. The CFS poorly predicts the meridional gradient in the tropical Atlantic Ocean. The superiority of the CFS predictions to the persistence forecasts depends on IC month, region, and lead time. The CFS prediction is generally better than the corresponding persistence forecast when the lead time is longer than 3 months. The most predictable pattern of SST in March has the same sign in almost the whole tropical Atlantic. The corresponding pattern in March is dominated by the same sign for geopotential height at 200 hPa in most of the domain and by significant opposite variation for precipitation between the northwestern tropical North Atlantic and the regions from tropical South America to the southwestern tropical North Atlantic. These predictable signals mainly result from the influence of the El Niño–Southern Oscillation (ENSO). The significant values in the most predictable pattern of precipitation in the regions from tropical South America to the southwestern tropical North Atlantic in March are associated with excessive divergence (convergence) at low (high) levels over these regions in the CFS. For the CFS, the predictive skill in the tropical Atlantic Ocean is largely determined by its ability to predict ENSO. This is due to the strong connection between ENSO and the most predictable patterns in the tropical Atlantic Ocean in the model. The higher predictive skill of tropical North Atlantic SST is consistent with the ability of the CFS to predict ENSO on interseasonal time scales, particularly for the ICs in warm months from March to October. In the southeastern ocean, the systematic warm bias is a crucial factor leading to the low skill in this region.

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Kolomijeca, Anna, Lukas Marx, Sarah Reynolds, Thierry Cariou, Edward Mawji et Cedric Boulart. « An update on dissolved methane distribution in the subtropical North Atlantic Ocean ». Ocean Science 18, n^o 5 (14 septembre 2022) : 1377–88. http://dx.doi.org/10.5194/os-18-1377-2022.

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Abstract. Methane (CH4) is a potent greenhouse gas and plays a significant role in recent increasing global temperatures. The oceans are a natural source of methane contributing to atmospheric methane concentrations, yet our understanding of the oceanic methane cycle is poorly constrained. Accumulating evidence indicates that a significant part of oceanic CH4 is produced in oxygenated surface waters as a by-product of phytoplanktonic activity. This study focused on the subtropical North Atlantic Ocean (26∘ N, 80′ W and 26∘ N, 18′ W) where the distribution of dissolved CH4 concentrations and associated air–sea fluxes during winter 2020 were investigated. Water samples from 64 stations were collected from the upper water column up to depths of 400 m. The upper oxic mixed layer was oversaturated in dissolved CH4 with concentrations ranging 3–7 nmol L−1, with the highest concentrations of 7–10 nmol L−1 found to the east of the transect, consistent with other subtropical regions of the world's oceans. The high anomalies of dissolved CH4 were found to be associated with phosphate-depleted waters and regions where the abundance of the ubiquitous picocyanobacteria Synechococcus and Prochlorococcus were elevated. Although other phytoplanktonic phyla cannot be excluded, this suggests that cyanobacteria contribute to the release of CH4 in this region. The calculation of air–sea fluxes further confirmed the subtropical North Atlantic Ocean as a source of CH4. This study provides evidence to corroborate the key role that picocyanobacteria play in helping to explain the oversaturation of CH4 found in surface mixed layer of the open ocean, otherwise known as the “ocean methane paradox”.

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Schuster, U., G. A. McKinley, N. Bates, F. Chevallier, S. C. Doney, A. R. Fay, M. González-Dávila et al. « Atlantic and Arctic sea-air CO<sub>2</sub> ; fluxes, 1990–2009 ». Biogeosciences Discussions 9, n^o 8 (9 août 2012) : 10669–724. http://dx.doi.org/10.5194/bgd-9-10669-2012.

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Abstract. The Atlantic and Arctic oceans are critical components of the global carbon cycle. Here we quantify the net sea-air CO2 flux, for the first time, across different methodologies for consistent time and space scales, for the Atlantic and Arctic basins. We present the long-term mean, seasonal cycle, interannual variability and trends in sea-air CO2 flux for the period 1990 to 2009, and assign an uncertainty to each. We use regional cuts from global observations and modelling products, specifically a pCO2-based CO2 flux climatology, flux estimates from the inversion of oceanic and atmospheric data, and results from six ocean biogeochemical models. Additionally, we use basin-wide flux estimates from surface ocean pCO2 observations based on two distinct methodologies. Our best estimate of the contemporary sea-to-air flux of CO2 (sum of anthropogenic and natural components) by the Atlantic between 40° S and 79° N is −0.49 ± 0.11 Pg C yr−1 and by the Arctic is −0.12 ± 0.06 Pg C yr−1, leading to a combined sea-to-air flux of −0.61 ± 0.12 Pg C yr−1 for the two decades (negative reflects ocean uptake). We do find broad agreement amongst methodologies with respect to the seasonal cycle in the subtropics of both hemispheres, but not elsewhere. Agreement with respect to detailed signals of interannual variability is poor; and correlations to the North Atlantic Oscillation are weaker in the North Atlantic and Arctic than in the equatorial region and South Subtropics. Linear trends for 1995 to 2009 indicate increased uptake and generally correspond between methodologies in the North Atlantic, but there is disagreement amongst methodologies in the equatorial region and South Subtropics.

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Schuster, U., G. A. McKinley, N. Bates, F. Chevallier, S. C. Doney, A. R. Fay, M. González-Dávila et al. « An assessment of the Atlantic and Arctic sea–air CO<sub>2</sub> ; fluxes, 1990–2009 ». Biogeosciences 10, n^o 1 (29 janvier 2013) : 607–27. http://dx.doi.org/10.5194/bg-10-607-2013.

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Abstract. The Atlantic and Arctic Oceans are critical components of the global carbon cycle. Here we quantify the net sea–air CO2 flux, for the first time, across different methodologies for consistent time and space scales for the Atlantic and Arctic basins. We present the long-term mean, seasonal cycle, interannual variability and trends in sea–air CO2 flux for the period 1990 to 2009, and assign an uncertainty to each. We use regional cuts from global observations and modeling products, specifically a pCO2-based CO2 flux climatology, flux estimates from the inversion of oceanic and atmospheric data, and results from six ocean biogeochemical models. Additionally, we use basin-wide flux estimates from surface ocean pCO2 observations based on two distinct methodologies. Our estimate of the contemporary sea–air flux of CO2 (sum of anthropogenic and natural components) by the Atlantic between 40° S and 79° N is −0.49 ± 0.05 Pg C yr−1, and by the Arctic it is −0.12 ± 0.06 Pg C yr−1, leading to a combined sea–air flux of −0.61 ± 0.06 Pg C yr−1 for the two decades (negative reflects ocean uptake). We do find broad agreement amongst methodologies with respect to the seasonal cycle in the subtropics of both hemispheres, but not elsewhere. Agreement with respect to detailed signals of interannual variability is poor, and correlations to the North Atlantic Oscillation are weaker in the North Atlantic and Arctic than in the equatorial region and southern subtropics. Linear trends for 1995 to 2009 indicate increased uptake and generally correspond between methodologies in the North Atlantic, but there is disagreement amongst methodologies in the equatorial region and southern subtropics.

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Lambert, Erwin, Tor Eldevik et Michael A. Spall. « On the Dynamics and Water Mass Transformation of a Boundary Current Connecting Alpha and Beta Oceans ». Journal of Physical Oceanography 48, n^o 10 (octobre 2018) : 2457–75. http://dx.doi.org/10.1175/jpo-d-17-0186.1.

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AbstractA subpolar marginal sea, like the Nordic seas, is a transition zone between the temperature-stratified subtropics (the alpha ocean) and the salinity-stratified polar regions (the beta ocean). An inflow of Atlantic Water circulates these seas as a boundary current that is cooled and freshened downstream, eventually to outflow as Deep and Polar Water. Stratification in the boundary region is dominated by a thermocline over the continental slope and a halocline over the continental shelves, separating Atlantic Water from Deep and Polar Water, respectively. A conceptual model is introduced for the circulation and water mass transformation in a subpolar marginal sea to explore the potential interaction between the alpha and beta oceans. Freshwater input into the shelf regions has a slight strengthening effect on the Atlantic inflow, but more prominently impacts the water mass composition of the outflow. This impact of freshwater, characterized by enhancing Polar Water outflow and suppressing Deep Water outflow, is strongly determined by the source location of freshwater. Concretely, perturbations in upstream freshwater sources, like the Baltic freshwater outflow into the Nordic seas, have an order of magnitude larger potential to impact water mass transports than perturbations in downstream sources like the Arctic freshwater outflow. These boundary current dynamics are directly related to the qualitative stratification in transition zones and illustrate the interaction between the alpha and beta oceans.

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Velo, A., F. F. Perez, P. Brown, T. Tanhua, U. Schuster et R. M. Key. « CARINA alkalinity data in the Atlantic Ocean ». Earth System Science Data Discussions 2, n^o 1 (3 août 2009) : 137–80. http://dx.doi.org/10.5194/essdd-2-137-2009.

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Abstract. Data on carbon and carbon-relevant hydrographic and hydrochemical parameters from previously non-publicly available cruise data sets in the Arctic, Atlantic and Southern Ocean have been retrieved and merged to a new database: CARINA (CARbon IN the Atlantic). These data have gone through rigorous quality control (QC) procedures to assure the highest possible quality and consistency. The data for most of the measured parameters in the CARINA data base were objectively examined in order to quantify systematic differences in the reported values, i.e. secondary quality control. Systematic biases found in the data have been corrected in the data products, i.e. three merged data files with measured, calculated and interpolated data for each of the three CARINA regions; Arctic, Atlantic and Southern Ocean. Out of a total of 188 cruise entries in the CARINA database, 98 were conducted in the Atlantic Ocean and of these, 75 cruises report alkalinity values. Here we present details of the secondary QC on alkalinity for the Atlantic Ocean part of CARINA. Procedures of quality control, including crossover analysis between cruises and inversion analysis of all crossover data are briefly described. Adjustments were applied to the alkalinity values for 16 of the cruises in the Atlantic Ocean region. With these adjustments the CARINA database is consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s. Based on our analysis we estimate the internal accuracy of the CARINA-ATL alkalinity data to be 3.3 μmol kg−1. The CARINA data are now suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation.

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Velo, A., F. F. Perez, P. Brown, T. Tanhua, U. Schuster et R. M. Key. « CARINA alkalinity data in the Atlantic Ocean ». Earth System Science Data 1, n^o 1 (27 novembre 2009) : 45–61. http://dx.doi.org/10.5194/essd-1-45-2009.

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Abstract. Data on carbon and carbon-relevant hydrographic and hydrochemical parameters from previously non-publicly available cruise data sets in the Arctic, Atlantic and Southern Ocean have been retrieved and merged to a new database: CARINA (CARbon IN the Atlantic). These data have gone through rigorous quality control (QC) procedures to assure the highest possible quality and consistency. The data for most of the measured parameters in the CARINA data base were objectively examined in order to quantify systematic differences in the reported values, i.e. secondary quality control. Systematic biases found in the data have been corrected in the data products, i.e. three merged data files with measured, calculated and interpolated data for each of the three CARINA regions; Arctic, Atlantic and Southern Ocean. Out of a total of 188 cruise entries in the CARINA database, 98 were conducted in the Atlantic Ocean and of these, 75 cruises report alkalinity values. Here we present details of the secondary QC on alkalinity for the Atlantic Ocean part of CARINA. Procedures of quality control, including crossover analysis between cruises and inversion analysis of all crossover data are briefly described. Adjustments were applied to the alkalinity values for 16 of the cruises in the Atlantic Ocean region. With these adjustments the CARINA database is consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s. Based on our analysis we estimate the internal accuracy of the CARINA-ATL alkalinity data to be 3.3 μmol kg−1. The CARINA data are now suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation.

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Zhao, Xia, et Jianping Li. « Winter-to-Winter Recurrence of Sea Surface Temperature Anomalies in the Northern Hemisphere ». Journal of Climate 23, n^o 14 (15 juillet 2010) : 3835–54. http://dx.doi.org/10.1175/2009jcli2583.1.

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Abstract The spatiotemporal characteristics of the winter-to-winter recurrence (WWR) of sea surface temperature anomalies (SSTA) in the Northern Hemisphere (NH) are comprehensively studied through lag correlation analysis. On this basis the relationships between the SSTA WWR and the WWR of the atmospheric circulation anomalies, El Niño–Southern Oscillation (ENSO), and SSTA interdecadal variability are also investigated. Results show that the SSTA WWR occurs over most parts of the North Pacific and Atlantic Oceans, but the spatiotemporal distributions of the SSTA WWR are distinctly different in these two oceans. Analyses indicate that the spatiotemporal distribution of the SSTA WWR in the North Atlantic Ocean is consistent with the spatial distribution of the seasonal cycle of its mixed layer depth (MLD), whereas that in the North Pacific Ocean, particularly the recurrence timing, cannot be fully explained by the change in the MLD between winter and summer in some regions. In addition, the atmospheric circulation anomalies also exhibit the WWR at the mid–high latitude of the NH, which is mainly located in eastern Asia, the central North Pacific, and the North Atlantic. The sea level pressure anomalies (SLPA) in the central North Pacific are essential for the occurrence of the SSTA WWR in this region. Moreover, the strongest positive correlation occurs when the SLPA lead SSTA in the central North Pacific by 1 month, which suggests that the atmospheric forcing on the ocean may play a dominant role in this region. Therefore, the “reemergence mechanism” is not the only process influencing the SSTA WWR, and the WWR of the atmospheric circulation anomalies may be one of the causes of the SSTA WWR in the central North Pacific. Finally, the occurrence of the SSTA WWR in the NH is closely related to SSTA interdecadal variability in the NH, but it is linearly independent of ENSO.

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Gleeson, Emily, Sarah Gallagher, Colm Clancy et Frédéric Dias. « NAO and extreme ocean states in the Northeast Atlantic Ocean ». Advances in Science and Research 14 (10 février 2017) : 23–33. http://dx.doi.org/10.5194/asr-14-23-2017.

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Abstract. Large scale atmospheric oscillations are known to have an influence on waves in the North Atlantic. In quantifying how the wave and wind climate of this region may change towards the end of the century due to climate change, it is useful to investigate the influence of large scale oscillations using indices such as the North Atlantic Oscillation (NAO: fluctuations in the difference between the Icelandic low pressure system and the Azore high pressure system). In this study a statistical analysis of the station-based NAO index was carried out using an ensemble of EC-Earth global climate simulations, where EC-Earth is a European-developed atmosphere ocean sea-ice coupled climate model. The NAO index was compared to observations and to projected changes in the index by the end of the century under the RCP4.5 and RCP8.5 forcing scenarios. In addition, an ensemble of EC-Earth driven WAVEWATCH III wave model projections over the North Atlantic was analysed to determine the correlations between the NAO and significant wave height (Hs) and the NAO and extreme ocean states. For the most part, no statistically significant differences were found between the distributions of observed and modelled station-based NAO or in projected distributions of the NAO. Means and extremes of Hs are projected to decrease on average by the end of this century. The 95th percentile of Hs is strongly positively correlated to the NAO. Projections of Hs extremes are location dependent and in fact, under the influence of positive NAO the 20-year return levels of Hs were found to be amplified in some regions. However, it is important to note that the projected decreases in the 95th percentile of Hs off the west coast of Ireland are not statistically significant in one of the RCP4.5 and one of the RCP8.5 simulations (me41, me83) which indicates that there is still uncertainty in the projections of higher percentiles.

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Gaetani, M., M. Baldi, G. A. Dalu et G. Maracchi. « Jetstream and rainfall distribution in the Mediterranean region ». Natural Hazards and Earth System Sciences 11, n^o 9 (19 septembre 2011) : 2469–81. http://dx.doi.org/10.5194/nhess-11-2469-2011.

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Abstract. This is a study on the impact of the jetstream in the Euro-Atlantic region on the rainfall distribution in the Mediterranean region; the study, based on data analysis, is restricted to the Mediterranean rainy season, which lasts from September to May. During this season, most of the weather systems originate over the Atlantic, and are carried towards the Mediterranean region by the westerly flow. In the upper troposphere of the Euro-Atlantic region this flow is characterized by two jets: the Atlantic jet, which crosses the ocean with a northeasterly tilt, and the African jet, which flows above the coast of North Africa. This study shows that the cross-jet circulation of the Atlantic jet favors storm activity in its exit region, while the cross-jet circulation of the African jet suppresses this kind of activity in its entrance region, with the 1st jet-stormtrack covariance mode explaining nearly 50% of the variability. It follows that the rainfall distribution downstream to these cross-jet circulations is strongly influenced by their relative positions. Specifically, in fall, rainfall is abundant in the western Mediterranean basin (WM), when the Atlantic jet is relatively strong but its northeasterly tilt is small, and the African jet is in its easternmost position. In winter, rainfall is abundant in the eastern Mediterranean basin (EM); this is when the Atlantic jet reaches the Scandinavian peninsula and the African jet is in its westernmost position. In spring, when the two jets weaken, the Atlantic jet retreats over the ocean, but the African jet stays in its winter position, rainfall is abundant in the Alpine region and in the Balkans. In addition, the covariance between precipitation and the jetstream has been evaluated. In fall, the latitudinal displacement of the Atlantic jet and the longitudinal displacement of the African jet modulate rainfall anomalies in the WM, with 38% explained covariance. In winter, the latitudinal displacement of the Atlantic jet produces rainfall anomalies in the western and central Mediterranean, with 45% explained covariance. In spring, the latitudinal displacement of the African jet produces rainfall anomalies, with 38% explained covariance.

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Yeager, Stephen, Alicia Karspeck, Gokhan Danabasoglu, Joe Tribbia et Haiyan Teng. « A Decadal Prediction Case Study : Late Twentieth-Century North Atlantic Ocean Heat Content ». Journal of Climate 25, n^o 15 (1 août 2012) : 5173–89. http://dx.doi.org/10.1175/jcli-d-11-00595.1.

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Abstract An ensemble of initialized decadal prediction (DP) experiments using the Community Climate System Model, version 4 (CCSM4) shows considerable skill at forecasting changes in North Atlantic upper-ocean heat content and surface temperature up to a decade in advance. Coupled model ensembles were integrated forward from each of 10 different start dates spanning from 1961 to 2006 with ocean and sea ice initial conditions obtained from a forced historical experiment, a Coordinated Ocean-Ice Reference Experiment with Interannual forcing (CORE-IA), which exhibits good correspondence with late twentieth-century ocean observations from the North Atlantic subpolar gyre (SPG) region. North Atlantic heat content anomalies from the DP ensemble correlate highly with those from the CORE-IA simulation after correcting for a drift bias. In particular, the observed large, rapid rise in SPG heat content in the mid-1990s is successfully predicted in the ensemble initialized in January of 1991. A budget of SPG heat content from the CORE-IA experiment sheds light on the origins of the 1990s regime shift, and it demonstrates the extent to which low-frequency changes in ocean heat advection related to the Atlantic meridional overturning circulation dominate temperature tendencies in this region. Similar budgets from the DP ensembles reveal varying degrees of predictive skill in the individual heat budget terms, with large advective heat flux anomalies from the south exhibiting the highest correlation with CORE-IA. The skill of the DP in this region is thus tied to correct initialization of ocean circulation anomalies, while external forcing is found to contribute negligibly (and for incorrect reasons) to predictive skill in this region over this time period.

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Han, Weiqing, Jérôme Vialard, Michael J. McPhaden, Tong Lee, Yukio Masumoto, Ming Feng et Will P. M. de Ruijter. « Indian Ocean Decadal Variability : A Review ». Bulletin of the American Meteorological Society 95, n^o 11 (1 novembre 2014) : 1679–703. http://dx.doi.org/10.1175/bams-d-13-00028.1.

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The international scientific community has highlighted decadal and multidecadal climate variability as a priority area for climate research. The Indian Ocean rim region is home to one-third of the world's population, mostly living in developing countries that are vulnerable to climate variability and to the increasing pressure of anthropogenic climate change. Yet, while prominent decadal and multidecadal variations occur in the Indian Ocean, they have been less studied than those in the Pacific and Atlantic Oceans. This paper reviews existing literature on these Indian Ocean variations, including observational evidence, physical mechanisms, and climatic impacts. This paper also identifies major issues and challenges for future Indian Ocean research on decadal and multidecadal variability.

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Marullo, Salvatore, Vincenzo Artale et Rosalia Santoleri. « The SST Multidecadal Variability in the Atlantic–Mediterranean Region and Its Relation to AMO ». Journal of Climate 24, n^o 16 (15 août 2011) : 4385–401. http://dx.doi.org/10.1175/2011jcli3884.1.

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Abstract Two sea surface temperature (SST) time series, the Extended Reconstructed SST version 3 (ERSST.v3) and the Hadley Centre Sea Ice and Sea Surface Temperature dataset (HadISST), are used to investigate SST multidecadal variability in the Mediterranean Sea and to explore possible connections with other regions of the global ocean. The consistency between these two time series and the original International Comprehensive Ocean–Atmosphere Dataset version 2.5 (ICOADS 2.5) over the Mediterranean Sea is investigated, evaluating differences from monthly to multidecadal scales. From annual to longer time scales, the two time series consistently describe the same trends and multidecadal oscillations and agree with Mediterranean ICOADS SSTs. At monthly time scales the two time series are less consistent with each other because of the evident annual cycle that characterizes their difference. The subsequent analysis of the Mediterranean annual SST time series, based on lagged-correlation analysis, multitaper method (MTM), and singular spectral analysis (SSA), revealed the presence of a significant oscillation with a period of about 70 yr, very close to that of the Atlantic multidecadal oscillation (AMO). An extension of the analysis to other World Ocean regions confirmed that the predominance of this multidecadal signal with respect to longer period trends is a unique feature of the Mediterranean and North Atlantic Ocean, where it reaches its maximum at subpolar latitudes. Signatures of multidecadal oscillations are also found in the global SST time series after removing centennial and longer-term components. The analysis also reveals that Mediterranean SST and North Atlantic indices are significantly correlated and coherent for periods longer than about 40 yr. For time scales in the range 40–55 yr the coherence between the Mediterranean and subpolar gyre temperatures is higher than the coherence between the Mediterranean SST and North Atlantic Oscillation (NAO) or AMO. Finally, the results of the analysis are discussed in the light of possible climate mechanisms that can couple the Mediterranean Sea with the North Atlantic and the Global Ocean.

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Tanhua, T., P. J. Brown et R. M. Key. « CARINA : nutrient data in the Atlantic Ocean ». Earth System Science Data Discussions 2, n^o 1 (17 juillet 2009) : 63–101. http://dx.doi.org/10.5194/essdd-2-63-2009.

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Abstract. Data on carbon and carbon-relevant hydrographic and hydrochemical parameters from previously non-publicly available cruise data sets in the Arctic, Atlantic and Southern Ocean have been retrieved and merged to a new database: CARINA (CARbon IN the Atlantic). These data have gone through rigorous quality control (QC) procedures to assure the highest possible quality and consistency. The data for most of the measured parameters in the CARINA data base were objectively examined in order to quantify systematic differences in the reported values, i.e. secondary quality control. Systematic biases found in the data have been corrected in the data products, i.e. three merged data files with measured, calculated and interpolated data for each of the three CARINA regions; Arctic, Atlantic and Southern Ocean. Out of a total of 188 cruise entries in the CARINA database, 98 were conducted in the Atlantic Ocean and of these 84 cruises report nitrate values, 79 silicate, and 78 phosphate. Here we present details of the secondary QC for nutrients for the Atlantic Ocean part of CARINA. Procedures of quality control, including crossover analysis between cruises and inversion analysis of all crossover data are briefly described. Adjustments were applied to the nutrient values for 43 of the cruises in the Atlantic Ocean region. With these adjustments the CARINA database is consistent both internally as well as with GLODAP data, an oceanographic data set based on the World Hydrographic Program in the 1990s (Key et al., 2004). Based on our analysis we estimate the internal accuracy of the CARINA-ATL nutrient data to be: nitrate 1.5%; phosphate 2.6%; silicate 3.1%. The CARINA data are now suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation.

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