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1
Kowalewska-Kalkowska, Halina, and Marek Kowalewski. "Combining Satellite Imagery and Numerical Modelling to Study the Occurrence of Warm Upwellings in the Southern Baltic Sea in Winter." Remote Sensing 11, no. 24 (December 12, 2019): 2982. http://dx.doi.org/10.3390/rs11242982.
Повний текст джерелаАнотація:
Coastal upwelling involves an upward movement of deeper, usually colder, water to the surface. Satellite sea surface temperature (SST) observations and simulations with a hydrodynamic model show, however, that the coastal upwelling in the Baltic Sea in winter can bring warmer water to the surface. In this study, the satellite SST data collected by the advanced very high resolution radiometer (AVHRR) and the moderate-resolution imaging spectroradiometer (MODIS), as well as simulations with the Parallel Model 3D (PM3D) were used to identify upwelling events in the southern Baltic Sea during the 2010–2017 winter seasons. The PM3D is a three-dimensional hydrodynamic model of the Baltic Sea developed at the Institute of Oceanography, University of Gdańsk, Poland, in which parallel calculations enable high-resolution modelling. A validation of the model results with in situ observations and satellite-derived SST data showed the PM3D to adequately represent thermal conditions in upwelling areas in winter (91.5% agreement). Analysis of the frequency of warm upwellings in 12 areas of the southern Baltic Sea showed a high variability in January and February. In those months, the upwelling was most frequent, both in satellite imagery and in model results, off the Hel Peninsula (38% and 43% frequency, respectively). Upwelling was also frequent off the Vistula Spit, west of the Island of Rügen, and off the eastern coast of Skåne, where the upwelling frequency estimated from satellite images exceeded 26%. As determined by the PM3D, the upwelling frequency off VS and R was at least 25%, while off the eastern coast of Skåne, it reached 17%. The faithful simulation of SST variability in the winters of 2010–2017 by the high-resolution model used was shown to be a reliable tool with which to identify warm upwellings in the southern Baltic Sea.
2
Yao, Zhongzhi, Wei Fan, Canbo Xiao, Tiancheng Lin, Yao Zhang, Yongyu Zhang, Jihua Liu, Zhujun Zhang, Yiwen Pan, and Ying Chen. "Numerical Studies on the Suitable Position of Artificial Upwelling in a Semi-Enclosed Bay." Water 12, no. 1 (January 8, 2020): 177. http://dx.doi.org/10.3390/w12010177.
Повний текст джерелаАнотація:
Ecological engineering by artificial upwelling is considered a promising way to improve water quality. Artificial upwelling could lift nutrient-rich bottom water to the surface, enhance seaweed growth and consequently increase nutrient removal from seawater. However, one of the major obstacles of the engineering application is to determine the suitable position of ecological engineering, which is critical for artificial upwelling’s performance. In this paper, potential artificial upwelling positions in a semi-closed bay are simulated by using the unstructured-grid Finite-Volume Coastal Ocean Model (FVCOM). The results show that the upwelling position with relative small tidal current and close to corner will be helpful to increasing nutrient concentration of surface water, and be appropriate to build the ecological engineering. With proper design of the ecological engineering, it is possible to have a noticeable impact in semi-closed bay. Thus, artificial upwelling has the potential to succeed as a promising way to alleviate the eutrophication.
3
González-Dávila, Melchor, J. Magdalena Santana Casiano, and Francisco Machín. "Changes in the partial pressure of carbon dioxide in the Mauritanian–Cap Vert upwelling region between 2005 and 2012." Biogeosciences 14, no. 17 (August 31, 2017): 3859–71. http://dx.doi.org/10.5194/bg-14-3859-2017.
Повний текст джерелаАнотація:
Abstract. Coastal upwellings along the eastern margins of major ocean basins represent regions of large ecological and economic importance due to the high biological productivity. The role of these regions for the global carbon cycle makes them essential in addressing climate change. The physical forcing of upwelling processes that favor production in these areas are already being affected by global warming, which will modify the intensity of upwelling and, consequently, the carbon dioxide cycle. Here, we present monthly high-resolution surface experimental data for temperature and partial pressure of carbon dioxide in one of the four most important upwelling regions of the planet, the Mauritanian–Cap Vert upwelling region, from 2005 to 2012. This data set provides direct evidence of seasonal and interannual changes in the physical and biochemical processes. Specifically, we show an upwelling intensification and an increase of 0.6 Tg yr−1 in CO2 outgassing due to increased wind speed, despite increased primary productivity. This increase in CO2 outgassing together with the observed decrease in sea surface temperature at the location of the Mauritanian Cap Blanc, 21° N, produced a pH rate decrease of −0.003 ± 0.001 yr−1.
4
Bakun, A. "Coastal Ocean Upwelling." Science 247, no. 4939 (January 12, 1990): 198–201. http://dx.doi.org/10.1126/science.247.4939.198.
Повний текст джерела
5
Hendry, Katharine, Oscar Romero, and Vanessa Pashley. "Nutrient utilization and diatom productivity changes in the low-latitude south-eastern Atlantic over the past 70 ka: response to Southern Ocean leakage." Climate of the Past 17, no. 2 (March 9, 2021): 603–14. http://dx.doi.org/10.5194/cp-17-603-2021.
Повний текст джерелаАнотація:
Abstract. Eastern boundary upwellings (EBUs) are some of the key loci of biogenic silica (opal) burial in the modern ocean, representing important productive coastal systems that extraordinarily contribute to marine organic carbon fixation. The Benguela upwelling system (BUS), in the low-latitude south-eastern Atlantic, is one of the major EBUs and is under the direct influence of nutrient-rich Southern Ocean waters. Quantification of past changes in diatom productivity through time, in response to late Quaternary climatic change, feeds into our understanding of the sensitivity of EBUs to future climatic perturbations. Existing sediment archives of silica cycling include opal burial fluxes, diatom assemblages, and opaline silicon isotopic variations (denoted by δ30Si). Burial fluxes and siliceous assemblages are limited to recording the remains reaching the sediment (i.e. export), and δ30Si variations are complicated by species-specific influences and seasonality. Here, we present the first combined δ30Si record of two large centric diatoms from the BUS, encompassing full glacial conditions to the Holocene. In addition to export, our new data allow us to reconstruct the utilization of dissolved Si in surface waters in an area with strong input from Southern Ocean waters. Our new archives show that there was enhanced upwelling of Southern Ocean Si-rich water accompanied by strong silicic acid utilization by coastal dwelling diatoms during Marine Isotope Stage 3 (MIS3; 60–40 ka). This pulse of strong silicic acid utilization was followed by a weakening of upwelling and coastal diatom Si utilization into MIS2, before an increase in pelagic diatom Si utilization across the deglaciation. We combine our findings with mass balance model experiments to show that changes in surface water silica cycling through time are a function of both upwelling intensity and utilization changes, illustrating the sensitivity of EBUs to climatic change on glacial–interglacial scales.
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Weldeab, S., J. B. W. Stuut, R. R. Schneider, and W. Siebel. "Holocene climate variability in the Winter Rainfall Zone of South Africa." Climate of the Past Discussions 9, no. 3 (May 7, 2013): 2309–56. http://dx.doi.org/10.5194/cpd-9-2309-2013.
Повний текст джерелаАнотація:
Abstract. We established a multi-proxy time series comprising analyses of major elements in bulk sediments, Sr and Nd isotopes and grain size of terrigenous fraction, and δ18O and δ13C in tests of Neogloboquadrina pachyderma (sinistral) from a marine sediment sequence recovered off the Orange River. The records reveal coherent patterns of variability that reflect changes in wind strength, precipitation over the river catchments, and upwelling of cold and nutrient-rich coastal waters off western South Africa. The wettest episode of the Holocene in the Winter Rainfall Zone (WRZ) of South Africa occurred during the "Little Ice Age" (700–100 yr BP). Wet phases were accompanied by strengthened coastal water upwellings, a decrease of Agulhas water leakage into the southern Atlantic, and a reduced dust incursion over Antarctica. A continuous aridification trend in the WRZ and a weakening of the southern Benguela Upwelling System (BUS) between 9000 and 5500 yr BP parallel with increase of dust deposition over Antarctica and an enhanced leakage of warm Agulhas water into the southeastern Atlantic. The temporal relationship between precipitation changes in the WRZ, the thermal state of the coastal surface water, and leakage of warm water in southern Atlantic, and variation of dust incursion over Antarctica suggests a causal link that most likely was related to latitudinal shifts of the Southern Hemisphere westerlies. Our results of the mid-Holocene time interval may serve as an analogue to a possible long-term consequence of the current and future southward shift of the westerlies that may result in a decline of rainfall over southwest Africa and a weakened upwelling with implication for phytoplankton productivity and fish stocks. Furthermore, warming of the coastal surface water as a result of warm Agulhas water incursion into the southern BUS may affect coastal fog formation that is critical as moisture source for the endemic flora of the Namaqualand.
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Shi, Weian, Zhi Huang, and Jianyu Hu. "Using TPI to Map Spatial and Temporal Variations of Significant Coastal Upwelling in the Northern South China Sea." Remote Sensing 13, no. 6 (March 11, 2021): 1065. http://dx.doi.org/10.3390/rs13061065.
Повний текст джерелаАнотація:
Based on Himawari-8 Sea Surface Temperature (SST) data and the semi-automatic Topographic Position Index (TPI)-based mapping method, this study maps the significant coastal upwelling in the northern South China Sea (NSCS). The results show that the Minnan coastal upwelling mainly occurs within 100 km off the south coast of Fujian; the Yuedong coastal upwelling appears to the east of Pearl River Estuary, limited to the area shallower than 40 m; and the Qiongdong coastal upwelling occurs most frequently in the area shallower than 75 m off the east coast of Hainan Island. Based on the results, this paper quantitatively describes the temporal and spatial variations of upwelling duration, influence area, upwelling SST anomaly, and chlorophyll-a (Chl-a) increase. Different coastal upwelling regions in the NSCS are significantly different in characteristics. The Qiongdong coastal upwelling has the longest duration and occurs most frequently, the Yuedong coastal upwelling has the largest influence area and Chl-a increase, and the Minnan coastal upwelling is quite strong in the NSCS.
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Langlet, D., L. Y. Alleman, P. D. Plisnier, H. Hughes, and L. André. "Mn seasonal upwellings recorded in Lake Tanganyika mussels." Biogeosciences Discussions 3, no. 5 (September 22, 2006): 1453–71. http://dx.doi.org/10.5194/bgd-3-1453-2006.
Повний текст джерелаАнотація:
Abstract. Biogenic productivity of Lake Tanganyika is highly dependent on seasonal upwellings of anoxic deep waters. We investigated the shell of freshwater bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes tuned by the monsoon regime. The results of a 2-years-long geochemical survey of the coastal waters performed on the dissolved and particulate fractions were put in perspective against laser ablation ICP-MS profiles of Mn in five aragonitic shells from the same lake location. Skeletal Mn profiles in 3 shells are very similar and dominated by episodic peaks that matched the Mn increase recorded in surface waters during the 2002 upwelling, while a shell collected during 2003 dry season detect both 2002 and 2003 upwelling events. Larger shells showing an extremely reduced growth display more than 8Mn peaks suggesting at least an 8 years record of seasonal changes in water composition.
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Huang, Zhi, Jianyu Hu, and Weian Shi. "Mapping the Coastal Upwelling East of Taiwan Using Geostationary Satellite Data." Remote Sensing 13, no. 2 (January 6, 2021): 170. http://dx.doi.org/10.3390/rs13020170.
Повний текст джерелаАнотація:
Coastal upwelling is important for coastal ecosystems and the blue economy because of its large productivity and large potential for catching fish. However, coastal upwelling along the Taiwan east coast has received little attention from the research community. This study used five-year daily Himawari-8 geostationary satellite sea surface temperature data to map the coastal upwelling east of Taiwan during the summer monsoon season. We applied a semi-automatic image process technique based on the topographic position index for the quantitative upwelling mapping. The results show clear evidence of seasonal coastal upwelling along the entire Taiwan east coast, mainly under the influence of upwelling-favorable southwesterly/southerly winds. There are three broad upwelling centers along the Taiwan east coast: north, central, and south. The upwelling around the northern center has the longest upwelling season, lasting from May to September. The upwelling extents are larger between June and August during the height of the summer monsoon.
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Weldeab, S., J. B. W. Stuut, R. R. Schneider, and W. Siebel. "Holocene climate variability in the winter rainfall zone of South Africa." Climate of the Past Discussions 8, no. 3 (June 18, 2012): 2281–320. http://dx.doi.org/10.5194/cpd-8-2281-2012.
Повний текст джерелаАнотація:
Abstract. We established a multi-proxy time series comprising analyses of major elements in bulk sediments, Sr and Nd isotopes, grain size of terrigenous fraction, and δ18O and δ13C in tests of Neogloboquadrina pachyderma (sinistral) from a marine sediment sequence recovered off the Orange River. The records reveal coherent patterns of variability that reflect changes in wind strength, precipitation over the river catchments, and upwelling of cold and nutrient-rich coastal waters off Western South Africa. The wettest episode of the Holocene in the Winter Rainfall Zone (WRZ) of South Africa occurred during the "Little Ice Age" (700–100 yr BP). Wet phases were accompanied by strengthened coastal water upwellings, a decrease of Agulhas water leakage into the Southern Atlantic, and a reduced dust incursion over Antarctica. A continuous aridification trend in the WRZ and a weakening of the Southern Benguela Upwelling System (BUS) between 9000 and 5500 yr BP parallel with evidence of a poleward shift of the austral mid-latitude westerlies and an enhanced leakage of warm Agulhas water into the Southeastern Atlantic. The temporal relationship between precipitation changes in the WRZ, the thermal state of the coastal surface water, and variation of dust incursion over Antarctica suggests a causal link that most likely was related to latitudinal shifts of the Southern Hemisphere westerlies and changes in the amount of Agulhas water leakage into the Southern BUS. Our results of the mid-Holocene time interval may serve as an analogue to a possible long-term consequence of the current and future southward shift of the westerlies that may result in a decline of rainfall over Southwest Africa and a weakened upwelling with implication for phytoplankton productivity and fish stocks. Furthermore, warming of the coastal surface water as a result of warm Agulhas water incursion into the Southern BUS may affect coastal fog formation that is critical as moisture source for the endemic flora of the Namaqualand.
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Abrahams, Amieroh, Robert W. Schlegel, and Albertus J. Smit. "A novel approach to quantify metrics of upwelling intensity, frequency, and duration." PLOS ONE 16, no. 7 (July 8, 2021): e0254026. http://dx.doi.org/10.1371/journal.pone.0254026.
Повний текст джерелаАнотація:
The importance of coastal upwelling systems is widely recognized. However, several aspects of the current and future behaviors of these systems remain uncertain. Fluctuations in temperature because of anthropogenic climate change are hypothesized to affect upwelling-favorable winds and coastal upwelling is expected to intensify across all Eastern Boundary Upwelling Systems. To better understand how upwelling may change in the future, it is necessary to develop a more rigorous method of quantifying this phenomenon. In this paper, we use SST data and wind data in a novel method of detecting upwelling signals and quantifying metrics of upwelling intensity, duration, and frequency at four sites within the Benguela Upwelling System. We found that indicators of upwelling are uniformly detected across five SST products for each of the four sites and that the duration of those signals is longer in SST products with higher spatial resolutions. Moreover, the high-resolution SST products are significantly more likely to display upwelling signals at 25 km away from the coast when signals were also detected at the coast. Our findings promote the viability of using SST and wind time series data to detect upwelling signals within coastal upwelling systems. We highlight the importance of high-resolution data products to improve the reliability of such estimates. This study represents an important step towards the development of an objective method for describing the behavior of coastal upwelling systems.
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Ribeiro, Flávia Noronha Dutra, Jacyra Soares, and Amauri Pereira de Oliveira. "The co-influence of the sea breeze and the coastal upwelling at Cabo Frio: a numerical investigation using coupled models." Brazilian Journal of Oceanography 59, no. 2 (June 2011): 131–44. http://dx.doi.org/10.1590/s1679-87592011000200002.
Повний текст джерелаАнотація:
A coupled atmospheric-oceanic model was used to investigate whether there is a positive feedback between the coastal upwelling and the sea breeze at Cabo Frio - RJ (Brazil). Two experiments were performed to ascertain the influence of the sea breeze on the coastal upwelling: the first one used the coupled model forced with synoptic NE winds of 8 m s-1 and the sign of the sea breeze circulation was set by the atmospheric model; the second experiment used only the oceanic model with constant 8 m s-1 NE winds. Then, to study the influence of the coastal upwelling on the sea breeze, two more experiments were performed: one using a coastal upwelling representative SST initial field and the other one using a constant and homogeneous SST field of 26°C. Finally, two more experiments were conducted to verify the influence of the topography and the spatial distribution of the sea surface temperature on the previous results. The results showed that the sea breeze can intensify the coastal upwelling, but the coastal upwelling does not intensify the sea breeze circulation, suggesting that there is no positive feedback between these two phenomena at Cabo Frio.
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Weldeab, S., J. B. W. Stuut, R. R. Schneider, and W. Siebel. "Holocene climate variability in the winter rainfall zone of South Africa." Climate of the Past 9, no. 5 (October 22, 2013): 2347–64. http://dx.doi.org/10.5194/cp-9-2347-2013.
Повний текст джерелаАнотація:
Abstract. We established a multi-proxy time series comprising analyses of major elements in bulk sediments, Sr and Nd isotopes, grain size of terrigenous fraction, and δ18O and δ13C in tests of Neogloboquadrina pachyderma (sinistral) from a marine sediment sequence recovered off the Orange River. The records reveal coherent patterns of variability that reflect changes in wind strength, precipitation over the river catchments, and upwelling of cold and nutrient-rich coastal waters off western South Africa. The wettest episode of the Holocene in the winter rainfall zone (WRZ) of South Africa occurred during the "Little Ice Age" (700–100 cal years BP) most likely in response to a northward shift of the austral westerlies. Wet phases and strengthened coastal water upwellings are companied by a decrease of Agulhas water leakage into the South Atlantic and a reduced dust incursion over Antarctica, as indicated in previous studies. A continuous aridification trend in the WRZ and a weakening of the southern Benguela Upwelling System (BUS) between 9000 and 5500 cal years BP parallel with increase of dust deposition over Antarctica and an enhanced leakage of warm Agulhas water into the eastern South Atlantic. The temporal relationship between precipitation changes in the WRZ, the thermal state of the coastal surface water, and leakage of warm water in the South Atlantic, and variation of dust incursion over Antarctica suggests a causal link that most likely was related to latitudinal shifts of the Southern Hemisphere westerlies. Our results of the mid-Holocene time interval may serve as an analogue to a possible long-term consequence of the current and future southward shift of the westerlies. Furthermore, warming of the coastal surface water as a result of warm Agulhas water incursion into the southern BUS may affect coastal fog formation.
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Lueker, T. J. "Coastal upwelling fluxes of O<sub>2</sub>, N<sub>2</sub>O, and CO<sub>2</sub> assessed from continuous atmospheric observations at Trinidad, California." Biogeosciences 1, no. 1 (November 16, 2004): 101–11. http://dx.doi.org/10.5194/bg-1-101-2004.
Повний текст джерелаАнотація:
Abstract. Continuous atmospheric records of O2/N2, CO2 and N2O obtained at Trinidad, California document the effects of air-sea exchange during coastal upwelling and plankton bloom events. The atmospheric records provide continuous observations of air-sea fluxes related to synoptic scale upwelling events over several upwelling seasons. Combined with satellite, buoy and local meteorology data, calculated anomalies in O2/N2 and N2O were utilized in a simple atmospheric transport model to compute air-sea fluxes during coastal upwelling. CO2 fluxes were linked to the oceanic component of the O2 fluxes through local hydrographic data and estimated as a function of upwelling intensity (surface ocean temperature and wind speed). Regional air-sea fluxes of O2/N2, N2O, and CO2 during coastal upwelling were estimated with the aid of satellite wind and SST data. Upwelling CO2 fluxes were found to represent ~10% of export production along the northwest coast of North America. Synoptic scale upwelling events impact the net exchange of atmospheric CO2 along the coastal margin, and will vary in response to the frequency and duration of alongshore winds that are subject to climate change.
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Lueker, T. J. "Coastal upwelling fluxes of O<sub>2</sub>, N<sub>2</sub>O, and CO<sub>2</sub> assessed from continuous atmospheric observations at Trinidad,California." Biogeosciences Discussions 1, no. 1 (August 13, 2004): 335–65. http://dx.doi.org/10.5194/bgd-1-335-2004.
Повний текст джерелаАнотація:
Abstract. Continuous atmospheric records of O2/N2, CO2 and N2O obtained at Trinidad, California document the effects of air-sea exchange during coastal upwelling and plankton bloom events. The atmospheric records provide continuous observations of air-sea fluxes related to synoptic scale upwelling events over several upwelling seasons. Combined with satellite, buoy and local meteorology data, calculated anomalies in O2/N2 and N2O were utilized in a simple atmospheric transport model to compute air-sea fluxes during coastal upwelling. CO2 fluxes were linked to the oceanic component of the O2 fluxes through local hydrographic data and estimated as a function of upwelling intensity (surface ocean temperature and wind speed). Regional air-sea fluxes of O2/N2O, and CO2 during coastal upwelling were estimated with the aid of satellite wind and SST data. Upwelling CO2 fluxes were found to represent ~10% of export production along the northwest coast of North America. Synoptic scale upwelling events impact the net exchange of atmospheric CO2 along the coastal margin, and will vary in response to the frequency and duration of alongshore winds that are subject to climate change.
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Djakouré, S., P. Penven, B. Bourlès, V. Koné, and J. Veitch. "Respective Roles of the Guinea Current and Local Winds on the Coastal Upwelling in the Northern Gulf of Guinea." Journal of Physical Oceanography 47, no. 6 (June 2017): 1367–87. http://dx.doi.org/10.1175/jpo-d-16-0126.1.
Повний текст джерелаАнотація:
AbstractThe northern Gulf of Guinea is a part of the eastern tropical Atlantic where oceanic conditions due to the presence of coastal upwelling may influence the regional climate and fisheries. The dynamics of this coastal upwelling is still poorly understood. A sensitivity experiment based on the Regional Oceanic Modeling System (ROMS) is carried out to assess the role of the detachment of the Guinea Current as a potential mechanism for coastal upwelling. This idealized experiment is performed by canceling the inertia terms responsible for the advection of momentum in the equations and comparing with a realistic experiment. The results exhibit two major differences. First, the Guinea Current is found to be highly sensitive to inertia, as it is no longer detached from the coast in the idealized experiment. The Guinea Current adjusts on an inertial boundary layer, the inertial terms defining its lateral extension. Second, the upwelling east of Cape Palmas disappears in absence of the Guinea Current detachment. This is in contrast with the upwelling east of Cape Three Points, which is still present. The results suggest that two different generation processes of the coastal upwelling need to be considered: the upwelling east of Cape Palmas (which is due to inertia, topographic variations, and advective terms effects resulting in important vertical pumping) and the upwelling east of Cape Three Points (which is principally induced by local winds). In addition to recent work ruling out the role of eddies, this study clarifies the processes responsible for this coastal upwelling.
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Bettencourt, João H., Vincent Rossi, Lionel Renault, Peter Haynes, Yves Morel, and Véronique Garçon. "Effects of upwelling duration and phytoplankton growth regime on dissolved-oxygen levels in an idealized Iberian Peninsula upwelling system." Nonlinear Processes in Geophysics 27, no. 2 (May 19, 2020): 277–94. http://dx.doi.org/10.5194/npg-27-277-2020.
Повний текст джерелаАнотація:
Abstract. We apply a coupled modelling system composed of a state-of-the-art hydrodynamical model and a low-complexity biogeochemical model to an idealized Iberian Peninsula upwelling system to identify the main drivers of dissolved-oxygen variability and to study its response to changes in the duration of the upwelling season and in the phytoplankton growth regime. We find that the export of oxygenated waters by upwelling front turbulence is a major sink for nearshore dissolved oxygen. In our simulations of summer upwelling, when the phytoplankton population is generally dominated by diatoms whose growth is boosted by nutrient input, net primary production and air–sea exchange compensate dissolved-oxygen depletion by offshore export over the shelf. A shorter upwelling duration causes a relaxation of upwelling winds and a decrease in offshore export, resulting in a slight increase of net dissolved-oxygen enrichment in the coastal region as compared to longer upwelling durations. When phytoplankton is dominated by groups less sensitive to nutrient inputs, growth rates decrease, and the coastal region becomes net heterotrophic. Together with the physical sink, this lowers the net oxygenation rate of coastal waters, which remains positive only because of air–sea exchange. These findings help in disentangling the physical and biogeochemical controls of dissolved oxygen in upwelling systems and, together with projections of increased duration of upwelling seasons and phytoplankton community changes, suggest that the Iberian coastal upwelling region may become more vulnerable to hypoxia and deoxygenation.
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Auger, Pierre-Amaël, Thomas Gorgues, Eric Machu, Olivier Aumont, and Patrice Brehmer. "What drives the spatial variability of primary productivity and matter fluxes in the north-west African upwelling system? A modelling approach." Biogeosciences 13, no. 23 (November 30, 2016): 6419–40. http://dx.doi.org/10.5194/bg-13-6419-2016.
Повний текст джерелаАнотація:
Abstract. A comparative box analysis based on a multi-decadal physical–biogeochemical hindcast simulation (1980–2009) was conducted to characterize the drivers of the spatial distribution of phytoplankton biomass and production in the north-west (NW) African upwelling system. Alongshore geostrophic flow related to large-scale circulation patterns associated with the influence of coastal topography is suggested to modulate the coastal divergence, and then the response of nutrient upwelling to wind forcing. In our simulation, this translates into a coastal upwelling of nitrate being significant in all regions but the Cape Blanc (CB) area. However, upwelling is found to be the dominant supplier of nitrate only in the northern Saharan Bank (NSB) and the Senegalo-Mauritanian (SM) regions. Elsewhere, nitrate supply is dominated by meridional advection, especially off Cape Blanc. Phytoplankton displays a similar behaviour with a supply by lateral advection which equals the net coastal phytoplankton growth in all coastal regions except the Senegalo-Mauritanian area. Noticeably, in the Cape Blanc area, the net coastal phytoplankton growth is mostly sustained by high levels of regenerated production exceeding new production by more than twofold, which is in agreement with the locally weak input of nitrate by coastal upwelling. Further offshore, the distribution of nutrients and phytoplankton is explained by the coastal circulation. Indeed, in the northern part of our domain (i.e. Saharan Bank), the coastal circulation is mainly alongshore, resulting in low offshore lateral advection of nutrients and phytoplankton. Conversely, lateral advection transports coastal nutrients and phytoplankton towards offshore areas in the latitudinal band off the Senegalo-Mauritanian region. Moreover, this latter offshore region benefits from transient southern intrusions of nutrient-rich waters from the Guinean upwelling.
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Narimousa, S., and T. Maxworthy. "Laboratory modeling of coastal upwelling." Eos, Transactions American Geophysical Union 67, no. 1 (1986): 2. http://dx.doi.org/10.1029/eo067i001p00002.
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Dabuleviciene, Toma, Igor E. Kozlov, Diana Vaiciute, and Inga Dailidiene. "Remote Sensing of Coastal Upwelling in the South-Eastern Baltic Sea: Statistical Properties and Implications for the Coastal Environment." Remote Sensing 10, no. 11 (November 6, 2018): 1752. http://dx.doi.org/10.3390/rs10111752.
Повний текст джерелаАнотація:
A detailed study of wind-induced coastal upwelling (CU) in the south-eastern Baltic Sea is presented based on an analysis of multi-mission satellite data. Analysis of moderate resolution imaging spectroradiometer (MODIS) sea surface temperature (SST) maps acquired between April and September of 2000–2015 allowed for the identification of 69 CU events. The Ekman-based upwelling index (UI) was applied to evaluate the effectiveness of the satellite measurements for upwelling detection. It was found that satellite data enable the identification of 87% of UI-based upwelling events during May–August, hence, serving as an effective tool for CU detection in the Baltic Sea under relatively cloud-free summer conditions. It was also shown that upwelling-induced SST drops, and its spatial properties are larger than previously registered. During extreme upwelling events, an SST drop might reach 14 °C, covering a total area of nearly 16,000 km2. The evolution of an upwelling front during such intensive events is accompanied by the generation of transverse filaments extending up to 70 km offshore. An analysis of the satellite optical data shows a clear decline in the chlorophyll-a concentration in the coastal zone and in the shallow Curonian Lagoon, where it drops down by an order of magnitude. It was also shown that a cold upwelling front alters the stratification in the atmospheric boundary layer, leading to a sudden drop of air temperature and near-surface winds.
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Marchesiello, Patrick, Mark T. Gibbs, and Jason H. Middleton. "Simulations of coastal upwelling on the Sydney Continental Shelf." Marine and Freshwater Research 51, no. 6 (2000): 577. http://dx.doi.org/10.1071/mf99046.
Повний текст джерелаАнотація:
Two-dimensional numerical simulations of the response of the coastal waters of Sydney, south-eastern Australia, to idealized upwelling-favourable winds are presented. The spin up of the upwelling circulation is investigated, in particular the structure of the nearshore circulation. The intensity of the final upwelling state is found to be strongly linked to the activation of the return flow through the bottom boundary layer, which is also related to the strength of imposed alongshore pressure gradients. Results from a simulation of upwelling forced by a deep-ocean alongshore-current jet also show the final upwelling state to be weak in comparison with upwelling states produced by the action of the local wind stress. Bottom boundary layer shut-down in the presence of such a forcing jet is also discussed. A simulation of a real upwelling event was also performed and good agreement was found between the simulation and observations from a field experiment performed during summer 1994 in the Sydney coastal ocean.
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Kikas, Villu, and Urmas Lips. "Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007–2013." Ocean Science 12, no. 3 (July 1, 2016): 843–59. http://dx.doi.org/10.5194/os-12-843-2016.
Повний текст джерелаАнотація:
Abstract. Ferrybox measurements have been carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) on a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll a fluorescence and turbidity and takes water samples for further analyses at a predefined time interval. We aimed to show how the Ferrybox technology could be used to study the coastal upwelling events in the Gulf of Finland. Based on the introduced upwelling index and related criteria, 33 coastal upwelling events were identified in May–September 2007–2013. The number of events, as well as the frequency of their occurrence and intensity expressed as a sum of daily average temperature deviations in the 20 km wide coastal area, were almost equal near the northern and southern coasts. Nevertheless, the wind impulse, which was needed to generate upwelling events of similar intensity, differed between the northern and southern coastal areas. It is suggested that the general thermohaline structure adapted to the prevailing forcing and the estuarine character of the basin weaken the upwelling created by the westerly to southwesterly (up-estuary) winds and strengthen the upwelling created by the easterly to northeasterly (down-estuary) winds. Two types of upwelling events were identified – one characterized by a strong temperature front and the other revealing gradual decrease in temperature from the open sea to the coastal area, with maximum temperature deviation close to the shore.
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Bednorz, Ewa, Marek Półrolniczak, and Arkadiusz M. Tomczyk. "Regional circulation patterns inducing coastal upwelling in the Baltic Sea." Theoretical and Applied Climatology 144, no. 3-4 (March 8, 2021): 905–16. http://dx.doi.org/10.1007/s00704-021-03539-7.
Повний текст джерелаАнотація:
AbstractAtmospheric feedback involved in the occurrence of coastal upwelling in a small semi-enclosed sea basin, i.e., the Baltic Sea, was analysed, and the regional circulation conditions triggering upwelling in different coastal sections were identified. Upwelling in the summer season (June–August, years 1982–2017) was recognized on the basis of sea surface temperature patterns. Circulation conditions were defined using (1) the established daily indices of zonal and meridional airflow and (2) the synoptic situation at sea level distinguished by applying rotated principal component analysis to sea level pressure data. The 12 daily synoptic patterns differed substantially in the intensity and location of their pressure centres. The mean seasonal frequency of upwelling was generally higher along the western Baltic shores than along the meridionally oriented eastern shores and varied from less than 10 to over 30% along the more predestined coastal sections, i.e., the northwestern coast of the Gulf of Bothnia, the northern Gulf of Finland and the southern Swedish coast. Due to the variable orientations of coastlines, upwelling could occur under almost any prevailing wind direction, and thus, each of the classified synoptic patterns could induce upwelling in some coastal sections. As deduced from the pressure fields for each circulation pattern, mostly alongshore winds triggered upwelling, which is in line with the Ekman rule. With time, upwelling could also be induced by the stress of normal to the coastline seaward winds.
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Kikas, V., and U. Lips. "Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007–2013." Ocean Science Discussions 12, no. 6 (November 20, 2015): 2863–98. http://dx.doi.org/10.5194/osd-12-2863-2015.
Повний текст джерелаАнотація:
Abstract. Ferrybox measurements are carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) in a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll a fluorescence and turbidity and takes water samples for further analyses at a pre-defined time interval. We aimed to show how the Ferrybox technology could be used to study the coastal upwelling events in the Gulf of Finland. Based on the introduced upwelling index and related criterion, 33 coastal upwelling events were identified in May–September 2007–2013. The number of events as well as frequency of their occurrence and intensity, expressed as a sum of daily average temperature deviations in the 20 km wide coastal area, were almost equal near the northern and southern coast. It is shown that the wind impulse needed to generate upwelling events of similar intensity differ between the two coastal areas whereas this difference is related to the average wind forcing in the area. Two types of upwelling events were identified – one characterized by a strong temperature front and the other revealing gradual decrease of temperature from the open to coastal area with maximum temperature deviation close to the shore.
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Escribano, R., E. Bustos-Ríos, P. Hidalgo, and C. E. Morales. "Growth and production of the copepod community in the southern area of the Humboldt Current System." Biogeosciences Discussions 12, no. 3 (February 10, 2015): 3057–99. http://dx.doi.org/10.5194/bgd-12-3057-2015.
Повний текст джерелаАнотація:
Abstract. Zooplankton production is a critical issue for understanding marine ecosystem structure and dynamics, however, its time-space variations are mostly unknown in most systems. In this study, estimates of copepod growth and production (CP) in the coastal upwelling and coastal transition zones off central-southern Chile (∼35–37° S) were obtained from annual cycles during a 3 year time series (2004, 2005, and 2006) at a fixed shelf station and from spring–summer surveys during the same years. C-specific growth rates (g) varied extensively among species and under variable environmental conditions; however, g values were not correlated to either near surface temperature or copepod size. Copepod biomass (CB) and CP were higher within the coastal upwelling zone (<50 km) and both decreased substantially from 2004 to 2006. Annual CP ranged between 24 and 52 g C m−2 year−1 with a~mean annual P/B ratio of 2.7. We estimated that CP could consume up to 60% of the annual primary production (PP) in the upwelling zone but most of the time is around 8%. Interannual changes in CB and CP values were associated with changes in the copepod community structure, the dominance of large-sized forms replaced by small-sized species from 2004 to 2006. This change was accompanied by more persistent and time extended upwelling during the same seasonal period. Extended upwelling may have caused large losses of CB from the upwelling zone due to an increase in offshore advection of coastal plankton. On a larger scale, these results suggest that climate-related impacts of increasing wind-driven upwelling in coastal upwelling systems may generate a negative trend in zooplankton biomass.
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Muni Krishna, K., V. Kovačević, and M. Gačić. "Coastal upwelling along the southwest coast of India – ENSO modulation." Ocean Science Discussions 5, no. 1 (April 21, 2008): 123–34. http://dx.doi.org/10.5194/osd-5-123-2008.
Повний текст джерелаАнотація:
Abstract. An index of El Niño Southern Oscillation (ENSO) in the Pacific during pre monsoon is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST) anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold) ENSO events being associated with relaxation (intensification) of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.
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Muni Krishna, K. "Coastal upwelling along the southwest coast of India – ENSO modulation." Annales Geophysicae 26, no. 6 (June 11, 2008): 1331–34. http://dx.doi.org/10.5194/angeo-26-1331-2008.
Повний текст джерелаАнотація:
Abstract. An index of El Niño Southern Oscillation (ENSO) in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST) anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold) ENSO events being associated with relaxation (intensification) of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.
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Jiang, Lide, Laurence C. Breaker, and Xiao-Hai Yan. "Upwelling age: an indicator of local tendency for coastal upwelling." Journal of Oceanography 68, no. 2 (December 31, 2011): 337–44. http://dx.doi.org/10.1007/s10872-011-0096-2.
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Largier, John L. "Upwelling Bays: How Coastal Upwelling Controls Circulation, Habitat, and Productivity in Bays." Annual Review of Marine Science 12, no. 1 (January 3, 2020): 415–47. http://dx.doi.org/10.1146/annurev-marine-010419-011020.
Повний текст джерелаАнотація:
Bays in coastal upwelling regions are physically driven and biochemically fueled by their interaction with open coastal waters. Wind-driven flow over the shelf imposes a circulation in the bay, which is also influenced by local wind stress and thermal bay–ocean density differences. Three types of bays are recognized based on the degree of exposure to coastal currents and winds (wide-open bays, square bays, and elongated bays), and the characteristic circulation and stratification patterns of each type are described. Retention of upwelled waters in bays allows for dense phytoplankton blooms that support productive bay ecosystems. Retention is also important for the accumulation of larvae, which accounts for high recruitment in bays. In addition, bays are coupled to the shelf ecosystem through export of plankton-rich waters during relaxation events. Ocean acidification and deoxygenation are a concern in bays because local extrema can develop beneath strong stratification.
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Reineck, H. E. "Coastal upwelling, its sediment record. Part A: Response of the sedimentary regime to present coastal upwelling; Part B: Sedimentary records of Ancient Coastal Upwelling." Earth-Science Reviews 22, no. 2 (September 1985): 170–71. http://dx.doi.org/10.1016/0012-8252(85)90036-4.
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Kämpf, J. "Phytoplankton blooms on the western shelf of Tasmania: evidence of a highly productive ecosystem." Ocean Science Discussions 11, no. 5 (September 15, 2014): 2173–204. http://dx.doi.org/10.5194/osd-11-2173-2014.
Повний текст джерелаАнотація:
Abstract. Analyses of >10 years of satellite-derived ocean-color data reveal the existence of a highly productive ecosystem on the west Tasmanian shelf. A closer event-based analysis indicates that the nutrient supply for this system has two different dynamical origins: (a) wind-driven coastal upwelling and (b) river plumes. During austral summer months, the west Tasmanian shelf forms a previously unknown upwelling center of the "Great South Australian Coastal Upwelling System", presumably injecting nutrient-rich water into western Bass Strait. Surprisingly, river discharges render the study region productive during other seasons of the year, except when nutrient-poor water of the South Australian Current reaches the region. Overall, the west Tasmanian shelf is more phytoplankton-productive than the long-known coastal upwelling along the Bonney Coast. The existence of phytoplankton blooms during the off-upwelling-season may explain the wintertime spawing aggregations of the blue grenadier (Macruronus novaezelandiae) and the associated regionally high abundance of Australian fur seals (Arctocephalus pusillus doriferus).
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Suprianto, A., A. S. Atmadipoera, and J. Lumban-Gaol. "Seasonal coastal upwelling in the Bali Strait: a model study." IOP Conference Series: Earth and Environmental Science 944, no. 1 (December 1, 2021): 012055. http://dx.doi.org/10.1088/1755-1315/944/1/012055.
Повний текст джерелаАнотація:
Abstract Bali Strait is part of fisheries management zone (WPP 573), where abundant fishery potential, of lemuru fish commodity. Here, physical oceanographic setting such as upwelling event plays an important role on maintaining high primary productivity and lemuru fish distribution. This study aims to describe physical process and dynamics of seasonal coastal upwelling using time-series datasets (2008 and 2014) of temperature, salinity, current velocity, surface chlorophyll-a (chl-a) from INDESO model and satellite imagery. The results showed that upwelling in the Bali Strait only during the southeast monsoon period when the south-easterly wind force surface Ekman drift of about 5.5 × 10−3 Sv flowing south-eastward (toward offshore). Upwelling event is characterized by minimum parameter of sea surface temperature (24.93 °C), and sea level anomaly (0.75 m), but maximum of surface chlorophyll-a (1.33 mg/m3). Furthermore, isotherm of 26 °C and Isohaline 33.7 psu are outcropped at sea surface in the center of upwelling zone. In contrast, during the nortwest monsoon period these isolines remain at deeper layer of about 80-90 m depth. Mean temperature-based upwelling index during peak of upwelling in August (1.19±0.19 °C). Upwelling impact on high abundance of lemuru fish (Sardinella sp.) production two month later after peak of chl-a.
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Lorente, Pablo, Silvia Piedracoba, Pedro Montero, Marcos G. Sotillo, María Isabel Ruiz, and Enrique Álvarez-Fanjul. "Comparative Analysis of Summer Upwelling and Downwelling Events in NW Spain: A Model-Observations Approach." Remote Sensing 12, no. 17 (August 26, 2020): 2762. http://dx.doi.org/10.3390/rs12172762.
Повний текст джерелаАнотація:
Upwelling and downwelling processes play a critical role in the connectivity between offshore waters and coastal ecosystems, having relevant implications in terms of intense biogeochemical activity and global fisheries production. A variety of in situ and remote-sensing networks were used in concert with the Iberia–Biscay–Ireland (IBI) circulation forecast system, in order to investigate two persistent upwelling and downwelling events that occurred in the Northwestern (NW) Iberian coastal system during summer 2014. Special emphasis was placed on quality-controlled surface currents provided by a high-frequency radar (HFR), since this land-based technology can effectively monitor the upper layer flow over broad coastal areas in near-real time. The low-frequency spatiotemporal response of the ocean was explored in terms of wind-induced currents’ structures and immediacy of reaction. Mean kinetic energy, divergence and vorticity maps were also calculated for upwelling and downwelling favorable events, in order to verify HFR and IBI capabilities, to accurately resolve the prevailing surface circulation features, such as the locus of a persistent upwelling maximum in the vicinity of Cape Finisterre. This integrated approach proved to be well-founded to efficiently portray the three-dimensional characteristics of the NW Iberian coastal upwelling system regardless of few shortcomings detected in IBI performance, such as the misrepresentation of the most energetic surface dynamics or the overestimation of the cooling and warming associated with upwelling and downwelling conditions, respectively. Finally, the variability of the NW Iberian upwelling system was characterized by means of the development of a novel ocean-based coastal upwelling index (UI), constructed from HFR-derived hourly surface current observations (UIHFR). The proposed UIHFR was validated against two traditional UIs for 2014, to assess its credibility. Results suggest that UIHFR was able to adequately categorize and characterize a wealth of summer upwelling and downwelling events of diverse length and strength, paving the way for future investigations of the subsequent biophysical implications.
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Zhang, Caiyun. "Responses of Summer Upwelling to Recent Climate Changes in the Taiwan Strait." Remote Sensing 13, no. 7 (April 3, 2021): 1386. http://dx.doi.org/10.3390/rs13071386.
Повний текст джерелаАнотація:
The response of a summer upwelling system to recent climate change in the Taiwan Strait has been investigated using a time series of sea surface temperature and wind data over the period 1982–2019. Our results revealed that summer upwelling intensities of the Taiwan Strait decreased with a nonlinear fluctuation over the past four decades. The average upwelling intensity after 2000 was 35% lower than that before 2000. The long-term changes in upwelling intensities show strong correlations with offshore Ekman transport, which experienced a decreasing trend after 2000. Unlike the delay effect of canonical ENSO events on changes in summer upwelling, ENSO Modoki events had a significant negative influence on upwelling intensity. Strong El Niño Modoki events were not favorable for the development of upwelling. This study also suggested that decreased upwelling could not slow down the warming rate of the sea surface temperature and would probably cause the decline of chlorophyll a in the coastal upwelling system of the Taiwan Strait. These results will contribute to a better understanding of the dynamic process of summer upwelling in the Taiwan Strait, and provide a sound scientific basis for evaluating future trends in coastal upwelling and their potential ecological effects.
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Steinfeldt, R., J. Sültenfuß, M. Dengler, T. Fischer, and M. Rhein. "Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium." Biogeosciences Discussions 12, no. 13 (July 14, 2015): 11019–59. http://dx.doi.org/10.5194/bgd-12-11019-2015.
Повний текст джерелаАнотація:
Abstract. Oceanic upwelling velocities are too small to be measured directly. The surface disequilibrium of the 3He/4He ratio provides an indirect method to infer vertical velocities at the base of the mixed layer. Samples of helium isotopes were taken from two coastal upwelling regions, off Peru on cruise M91, and off Mauritania on 3 cruises. The helium-3 flux into the mixed layer also depends on the diapycnal mixing. Direct observations of the vertical diffusivity have been performed on all 4 cruises and are also used in this study. The resulting upwelling velocities in the coastal regions vary between 1.1 × 10−5 and 2.8 × 10−5 m s−1 for all cruises. Vertical velocities off the equator can also be inferred from the divergence of the wind driven Ekman transport. In the coastal regimes, the agreement between wind and helium derived upwelling is fairly good at least for the mean values. Further offshore, the helium derived upwelling still reaches 1 × 10−5 m s−1, whereas the wind driven upwelling from Ekman suction is smaller by at least one order of magnitude. One reason for this difference might be eddy induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium derived vertical velocities and the measured vertical diffusivities. The advective part of these fluxes makes up at least 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 g C m2 d−1 off Peru and 1.6–1.9 g C m2 d−1 off Mauritania.
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He, Yuxin, Bangqi Hu, Jun Li, Hongxuan Lu, Hong Yan, Liang Dong, and Xin Zhou. "Late-Holocene variation in vertical thermal gradient from the coastal East China Sea: Links to monsoon climate and coastal upwelling." Holocene 29, no. 2 (November 16, 2018): 209–18. http://dx.doi.org/10.1177/0959683618810399.
Повний текст джерелаАнотація:
The evolution history of coastal upwelling systems in the East China Sea over the late-Holocene are important yet difficult to be characterized. Here, we present ~3000-year temperature records based on both alkenones (UK’37) and glycerol dialkyl glycerol tetraethers (TEXH86) from a sedimentary core in the coastal upwelling site of the southern East China Sea. By examining the similarity and difference between the down-core TEXH86-derived temperature and records of sea surface temperature, summer monsoon, and winter monsoon, we suggest that the TEXH86 mainly reflects temperature in the subsurface water in the studied site. In this sense, paired temperature records from both surface (UK’37) and subsurface (TEXH86) water would yield an estimation on the vertical thermal gradient, which provides insight into the upwelling strength in the summer season. Weak upwelling periods occurred at 2600–2800 yr BP, 2000–2400 yr BP, 1200–1550 yr BP, 350–750 yr BP, and the recent ~100 years. Positive correlations among the coastal upwelling, the Asian summer monsoon, and the solar irradiance in centennial scales at ~100–3000 yr BP indicate that solar-induced summer monsoonal wind might be responsible for the coastal upwelling in the studied area. However, weak upwelling intensity and weak monsoonal strength under the background of relatively warm global temperature and strong solar irradiance since the end of the ‘Little Ice Age’ (LIA) might suggest a different climatic response to the natural irradiance, asking for further work on the underlying mechanisms of this phenomenon in a widespread area.
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Narayan, N., A. Paul, S. Mulitza, and M. Schulz. "Trends in coastal upwelling intensity during the late 20th century." Ocean Science Discussions 7, no. 1 (February 19, 2010): 335–60. http://dx.doi.org/10.5194/osd-7-335-2010.
Повний текст джерелаАнотація:
Abstract. This study presents linear trends of coastal upwelling intensity in the later part of the 20th century (1960–2001) employing various indices of upwelling, derived from meridional wind stress and sea surface temperature. The analysis was conducted in the four major coastal upwelling regions in the world, which are off North-West Africa, Lüderitz, California and Peru respectively. The trends in meridional wind stress showed a steady increase of intensity from 1960–2001, which was also reflected in the SST index calculated for the same time period. The steady cooling observed in the instrumental records of SST off California substantiated this observation further. Correlation analysis showed that basin-scale oscillations like the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) could not be directly linked to the observed increase of upwelling intensity off NW Africa and California respectively. The relationship of the North Atlantic Oscillation (NAO) with coastal upwelling off NW Africa turned out to be ambiguous due to a negative correlation between the NAO index and the meridional wind stress and a lack of correlation with the SST index. Our results give additional support to the hypothesis that the coastal upwelling intensity increases globally because of raising greenhouse gas concentrations in the atmosphere and an associated increase of the land-sea pressure gradient and meridional wind stress.
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Wang, Bin, Lei Wu, Ning Zhao, Tianran Liu, and Naoki Hirose. "Summer Wind Effects on Coastal Upwelling in the Southwestern Yellow Sea." Journal of Marine Science and Engineering 9, no. 9 (September 17, 2021): 1021. http://dx.doi.org/10.3390/jmse9091021.
Повний текст джерелаАнотація:
The features of coastal upwelling in the southwestern Yellow Sea were investigated based on oceanology data from a research cruise and a regional circulation model. The observation data suggest that a relatively colder and saltier water core exists from the deeper layer to the surface, off the Subei Bank. The concentrations of nutrients also suggest that coastal upwelling is beneficial for nutrient enrichment in the upper layer. The numerical simulations are in good agreement with oceanology observations. Furthermore, sensitivity experiments indicate that, in addition to the tidal-induced upwelling and tidal mixing proposed in previous studies, the summer monsoon is also critical to vertical circulation in the southwestern Yellow Sea. The southwesterly wind stress and positive wind stress curl make considerable contributions to upwelling off the Subei coast compared with tidal motions. Moreover, this study also proposes that changes in the summer monsoon and its curl may have been helpful to the formation of upwelling during the past decade, which may have provided a favorable marine environment for the frequent occurrence of green tides. This study provides a theoretical basis for the mechanisms of coastal upwelling and the nitrogen cycle in the Yellow Sea.
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Steinfeldt, R., J. Sültenfuß, M. Dengler, T. Fischer, and M. Rhein. "Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium." Biogeosciences 12, no. 24 (December 21, 2015): 7519–33. http://dx.doi.org/10.5194/bg-12-7519-2015.
Повний текст джерелаАнотація:
Abstract. Upwelling is an important process, bringing gases and nutrients into the ocean mixed layer. The upwelling velocities, however, are too small to be measured directly. Here we use the surface disequilibrium of the 3He / 4He ratio measured in two coastal upwelling regions off Peru in the Pacific ocean and off Mauritania in the Atlantic ocean to calculate the regional distribution of vertical velocities. To also account for the fluxes by diapycnal mixing, microstructure-based observations of the vertical diffusivity have been performed on all four cruises analysed in this study. The upwelling velocities in the coastal regions vary between 1.1 ± 0.3 × 10−5 and 2.8 ± 1.5 × 10−5 m s−1 for all cruises. Vertical velocities are also inferred from the divergence of the wind-driven Ekman transport. In the coastal regimes, both methods agree within the error range. Further offshore, the helium-derived vertical velocity still reaches 1 × 10−5 m s−1, whereas the wind-driven upwelling from Ekman suction is smaller by up to 1 order of magnitude. One reason for this difference is ascribed to eddy-induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium-derived vertical velocities and the vertical diffusivities. The advective part of these fluxes makes up at about 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 ± 0.3 g C m2 d−1 off Peru and 1.6–2.1 ± 0.5 g C m2 d−1 off Mauritania.
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Perlin, Natalie, Eric D. Skyllingstad, Roger M. Samelson, and Philip L. Barbour. "Numerical Simulation of Air–Sea Coupling during Coastal Upwelling." Journal of Physical Oceanography 37, no. 8 (August 1, 2007): 2081–93. http://dx.doi.org/10.1175/jpo3104.1.
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Abstract Air–sea coupling during coastal upwelling was examined through idealized three-dimensional numerical simulations with a coupled atmosphere–ocean mesoscale model. Geometry, topography, and initial and boundary conditions were chosen to be representative of summertime coastal conditions off the Oregon coast. Over the 72-h simulations, sea surface temperatures were reduced several degrees near the coast by a wind-driven upwelling of cold water that developed within 10–20 km off the coast. In this region, the interaction of the atmospheric boundary layer with the cold upwelled water resulted in the formation of an internal boundary layer below 100-m altitude in the inversion-capped boundary layer and a reduction of the wind stress in the coupled model to half the offshore value. Surface heat fluxes were also modified by the coupling. The simulated modification of the atmospheric boundary layer by ocean upwelling was consistent with recent moored and aircraft observations of the lower atmosphere off the Oregon coast during the upwelling season. For these 72-h simulations, comparisons of coupled and uncoupled model results showed that the coupling caused measurable differences in the upwelling circulation within 20 km off the coast. The coastal Ekman transport divergence was distributed over a wider offshore extent and a thinner ocean surface boundary layer, with consistently smaller offshore and depth-integrated alongshore transport formed in the upwelling region, in the coupled case relative to the uncoupled case. The results indicate that accurate models of coastal upwelling processes can require representations of ocean–atmosphere interactions on short temporal and horizontal scales.
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Cline, Joel D. "Coastal upwelling, its sediment record, part a: Responses of the sedimentary regime to present coastal upwelling; and part b: Sedimentary records of ancient coastal upwelling." Chemical Geology 51, no. 1-2 (October 1985): 152–53. http://dx.doi.org/10.1016/0009-2541(85)90098-1.
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Li, Yuhui, Yun Qiu, Jianyu Hu, Cherry Aung, Xinyu Lin, and Yue Dong. "Springtime Upwelling and Its Formation Mechanism in Coastal Waters of Manaung Island, Myanmar." Remote Sensing 12, no. 22 (November 18, 2020): 3777. http://dx.doi.org/10.3390/rs12223777.
Повний текст джерелаАнотація:
Multisource satellite remote sensing data and the World Ocean Atlas 2018 (WOA18) temperature and salinity dataset have been used to analyze the spatial distribution, variability and possible forcing mechanisms of the upwelling off Manaung Island, Myanmar. Signals of upwelling exist off the coasts of Manaung Island, in western Myanmar during spring. It appears in February, reaches its peak in March and decays in May. Low-temperature (<28.3 °C) and high-salinity (>31.8 psu) water at the surface of this upwelling zone is caused by the upwelling of seawater from a depth below 100 m. The impact of the upwelling on temperature is more significant in the subsurface layer than that in the surface layer. In contrast, the impact of the upwelling on salinity in the surface layer is more significant. Further research reveals that the remote forcing from the equator predominantly induces the evolution of the upwelling, while the local wind forcing also contributes to strengthen the intensity of the upwelling during spring.
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Huang, Haocai, Yong Guo, Zhikun Wang, Yun Shen, and Yan Wei. "Water Temperature Observation by Coastal Acoustic Tomography in Artificial Upwelling Area." Sensors 19, no. 12 (June 12, 2019): 2655. http://dx.doi.org/10.3390/s19122655.
Повний текст джерелаАнотація:
Artificial upwelling is a geoengineering method to repair and improve marine ecosystems, and its operation requires long-term and continuous temperature field observation. However, existing methods are rarely seen to accomplish such observation. In this study, we investigate the coastal acoustic tomography (CAT) to obtain the long-term horizontal temperature field of an artificial upwelling area in an anechoic tank. We conduct four sets of experiments with different CAT station numbers and compare their data with those collected from temperature sensors. By analyzing the travel time from the CAT experiments, the horizontal temperature field of the upwelling area could be mapped. The CAT results and the comparison results show that the surface temperature of the observed area decreases by approximately 3 °C after upwelling, while the temperature of where the CAT is deployed decreases by about 1 °C; the temperature is lowest at the center of the upwelling area. Increasing the number of stations and station spacing would improve the temperature mapping accuracy. Therefore, the feasibility of using the CAT system to observe artificial upwelling is proved valid. This study indicates the potential application of CAT in temperature field observation in artificial upwelling area in the sea.
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Narayan, N., A. Paul, S. Mulitza, and M. Schulz. "Trends in coastal upwelling intensity during the late 20th century." Ocean Science 6, no. 3 (September 22, 2010): 815–23. http://dx.doi.org/10.5194/os-6-815-2010.
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Abstract. This study presents linear trends of coastal upwelling intensity in the later part of the 20th century (1960–2001) employing various indices of upwelling, derived from meridional wind stress and sea surface temperature. The analysis was conducted in the four major coastal upwelling regions in the world, which are off North-West Africa, Lüderitz, California and Peru. The trends in meridional wind stress showed a steady increase of intensity from 1960–2001, which was also reflected in the SST index calculated for the same time period. The steady cooling observed in the instrumental records of SST off California substantiated this observation further. It was also noted that the trends in meridional wind stress obtained from different datasets differ substantially from each other. Correlation analysis showed that basin-scale oscillations like the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) could not be directly linked to the observed increase of upwelling intensity off NW Africa and California respectively. The relationship of the North Atlantic Oscillation (NAO) with coastal upwelling off NW Africa turned out to be ambiguous due to a negative correlation between the NAO index and the meridional wind stress and a lack of correlation with the SST index. Our results give additional support to the hypothesis that the coastal upwelling intensity increases globally because of raising greenhouse gas concentrations in the atmosphere and an associated increase of the land-sea pressure gradient and meridional wind stress.
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Raimund, S., B. Quack, Y. Bozec, M. Vernet, V. Rossi, V. Garçon, Y. Morel, and P. Morin. "Sources of short-lived bromocarbons in the Iberian upwelling system." Biogeosciences Discussions 7, no. 6 (November 30, 2010): 8663–97. http://dx.doi.org/10.5194/bgd-7-8663-2010.
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Abstract. Seawater concentrations of the four brominated trace gases dibromomethane (CH2Br2), bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl) and bromoform (CHBr3) were measured at different depths of the water column in the Iberian upwelling off Portugal during summer 2007. Bromocarbon concentrations showed elevated values in recently upwelled and aged upwelled waters (mean values of 30 pmol L−1 for CHBr3), while values in the open ocean were significantly lower (7.4 pmol L−1 for CHBr3). Correlations with biological variables and marker pigments indicated that phytoplankton could be identified as a weak bromocarbon source in the open ocean. In upwelled water masses along the coast, halocarbons were not correlated to Chl-a, indicating an external source, overlapping the possible internal production by phytoplankton. We showed that the tidal frequency had a significant influence on halocarbon concentrations in the upwelling and we linked those findings to a strong intertidal coastal source, as well as to a transport of those halocarbon enriched coastal waters by westward surface upwelling currents. Coastal sources and transport can be accounted for maximum values of up to 185.1 pmol L−1 CHBr3 in the upwelling. Comparison with other productive marine areas revealed that the Iberian upwelling had stronger halocarbon sources than the phytoplankton dominated sources in the Mauritanian upwelling. However, the concentrations off the Iberian Peninsula were still much lower than those of coastal macroalgal influenced waters or those of polar regions dominated by cold water adapted diatoms.
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Dabuleviciene, Toma, Diana Vaiciute, and Igor E. Kozlov. "Chlorophyll-a Variability during Upwelling Events in the South-Eastern Baltic Sea and in the Curonian Lagoon from Satellite Observations." Remote Sensing 12, no. 21 (November 8, 2020): 3661. http://dx.doi.org/10.3390/rs12213661.
Повний текст джерелаАнотація:
Based on the analysis of multispectral satellite data, this work demonstrates the influence of coastal upwelling on the variability of chlorophyll-a (Chl-a) concentration in the south-eastern Baltic (SEB) Sea and in the Curonian Lagoon. The analysis of sea surface temperature (SST) data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua/Terra satellites, together with Chl-a maps from Medium Resolution Imaging Spectrometer (MERIS) onboard Envisat, shows a significant decrease of up to 40–50% in Chl-a concentration in the upwelling zone. This results from the offshore Ekman transport of more productive surface waters, which are replaced by cold and less-productive waters from deeper layers. Due to an active interaction between the Baltic Sea and the Curonian Lagoon which are connected through the Klaipeda Strait, coastal upwelling in the SEB also influences the hydrobiological conditions of the adjacent lagoon. During upwelling inflows, SST drops by approximately 2–8 °C, while Chl-a concentration becomes 2–4 times lower than in pre-upwelling conditions. The joint analysis of remotely sensed Chl-a and SST data reveals that the upwelling-driven reduction in Chl-a concentration leads to the temporary improvement of water quality in terms of Chl-a in the coastal zone and in the hyper-eutrophic Curonian Lagoon. This study demonstrates the benefits of multi-spectral satellite data for upscaling coastal processes and monitoring the environmental status of the Baltic Sea and its largest estuarine lagoon.
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Bonino, Giulia, Elisa Lovecchio, Nicolas Gruber, Matthias Münnich, Simona Masina, and Doroteaciro Iovino. "Drivers and impact of the seasonal variability of the organic carbon offshore transport in the Canary upwelling system." Biogeosciences 18, no. 8 (April 19, 2021): 2429–48. http://dx.doi.org/10.5194/bg-18-2429-2021.
Повний текст джерелаАнотація:
Abstract. The Canary upwelling system (CanUS) is a productive coastal region characterized by strong seasonality and an intense offshore transport of organic carbon (Corg) to the adjacent oligotrophic offshore waters. There, the respiration of this Corg substantially modifies net community production (NCP). While this transport and the resulting coupling of the biogeochemistry between the coastal and open ocean has been well studied in the annual mean, the temporal variability, and especially its seasonality, has not yet been investigated. Here, we determine the seasonal variability of the offshore transport of Corg, its mesoscale component, latitudinal differences, and the underlying physical and biological drivers. To this end, we employ the Regional Ocean Modeling System (ROMS) coupled to a nutrient–phytoplankton–zooplankton–detritus (NPZD) ecosystem model. Our results reveal the importance of the mesoscale fluxes and of the upwelling processes (coastal upwelling and Ekman pumping) in modulating the seasonal variation of the offshore Corg transport. We find that the region surrounding Cape Blanc (21∘ N) hosts the most intense Corg offshore flux in every season, linked to the persistent, and far reaching Cape Blanc filament and its interaction with the Cape Verde Front. Coastal upwelling filaments dominate the seasonality of the total offshore flux up to 100 km from the coast, contributing in every season at least 80 % to the total flux. The seasonality of the upwelling modulates the offshore Corg seasonality hundreds of kilometers from the CanUS coast via lateral redistribution of nearshore production. North of 24.5∘ N, the sharp summer–fall peak of coastal upwelling results in an export of more than 30 % of the coastal Corg at 100 km offshore due to a combination of intensified nearshore production and offshore fluxes. To the south, the less pronounced upwelling seasonality regulates an overall larger but farther-reaching and less seasonally varying lateral flux, which exports between 60 % and 90 % of the coastal production more than 100 km offshore. Overall, we show that the temporal variability of nearshore processes modulates the variability of Corg and NCP hundreds of kilometers offshore from the CanUS coast via the offshore transport of the nearshore production.
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Umasangaji, H., and Y. Ramili. "Mini review: Characteristics of upwelling in several coastal areas in the world." IOP Conference Series: Earth and Environmental Science 890, no. 1 (October 1, 2021): 012004. http://dx.doi.org/10.1088/1755-1315/890/1/012004.
Повний текст джерелаАнотація:
Abstract This paper provides an overview of the upwelling processes and the controlling factors as an effort to reveal the characteristics and the intensities of upwelling events in several parts of the world. This review aimed at identifying the characteristics of upwelling and how the global climate controlling this physic phenomenon such as ENSO, IOD and Kelvin Wave. Several places in the Southeast Asia experienced high intensities of upwelling when El Nino events such as in South of Java, East Coast of Malaysia Peninsula and in Vietnam Coastal area. The results of this review found that area with the most intensive and productive upwelling in the world is South American waters and Banguela Upwelling System (BUS) in the African Coast. However, several other areas also show intensive and high productivity of upwelling, such as off the southern coast of Java Island in Indonesia and the Banda Sea and its surroundings. It is found that upwelling with stronger intensity can result in increase of mortality of certain organisms such as scallops. Additionally, increase of nutrients in a waters is often accompanied by an increase in several species of toxic algae that are harmful to the local fishery system (harmful algae blooms, HABs).
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Di Lorenzo, Emanuele. "The future of coastal ocean upwelling." Nature 518, no. 7539 (February 2015): 310–11. http://dx.doi.org/10.1038/518310a.
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Capet, X. J., P. Marchesiello, and J. C. McWilliams. "Upwelling response to coastal wind profiles." Geophysical Research Letters 31, no. 13 (July 2004): n/a. http://dx.doi.org/10.1029/2004gl020123.
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