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SCARABINO, FABRIZIO, RUDÁ AMORIM LUCENA, TOMÁS MUNILLA, ANNA SOLER-MEMBRIVES, LEONARDO ORTEGA, EVANGELINA SCHWINDT, GUZMÁN LÓPEZ, JOSÉ MARÍA ORENSANZ et MARTIN LIDSEY CHRISTOFFERSEN. « Pycnogonida (Arthropoda) from Uruguayan waters (Southwest Atlantic) : annotated checklist and biogeographic considerations ». Zootaxa 4550, no 2 (24 janvier 2019) : 185. http://dx.doi.org/10.11646/zootaxa.4550.2.2.
Texte intégralRésumé :
Records of pycnogonids from Uruguayan waters (south-western Atlantic) include 26 species cited from precise locations, and at least five other species based on unconfirmed records. Nearly half of the species in that fauna belong to the genus Nymphon (12 spp.). Most species (22) come from deep-water and were recorded and described by C. A. Child. Of these, at least twelve species have an extended Antarctic and Subantarctic distribution, showing the influence of these cold waters in the area; three others have a wide deep-sea distribution pattern. Five species are known only from the lower slope and abyssal basin off La plata river: Mimipallene Atlantis and four species of Nymphon. Records from coastal and shelf areas (four species) are poorly documented and should be the focus of future research. Of these, Colossendeis geoffroyi is considered endemic in the Southwest Atlantic between 34ºS and 40ºS, but presents clear Antarctic affinities. A small-sized species living in shallow waters, Pycnogonum cessaci, is here considered as cryptogenic.
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ALVES-JÚNIOR, FLAVIO DE ALMEIDA, RACHEL DE JESUS FEIO DE LEMOS, IRENE AZEVEDO CARDOSO, MARINA DE SÁ LEITÃO CÂMARA DE ARAÚJO, ARNAUD BERTRAND et JESSER F. SOUZA-FILHO. « New records of deep-sea prawn of the genus Gennadas Spence Bate, 1881 (Crustacea : Decapoda : Benthesicymidae) from Southwestern Atlantic ». Zootaxa 4450, no 3 (25 juillet 2018) : 376. http://dx.doi.org/10.11646/zootaxa.4450.3.4.
Texte intégralRésumé :
Here, we report the new occurrences of four deep-water prawn of the genus Gennadas in the southwestern Atlantic: G. gilchristi recorded from the Mid-Atlantic Ridge region; G. capensis recorded from Brazilian waters off Fernando de Noronha Archipelago, Atol das Rocas and Ceará Chain; G. talismani and G. scutatus recorded both to Mid-Atlantic Ridge and to Brazilian waters.
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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.
Texte intégralRésumé :
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.
Texte intégralRésumé :
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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Pautova, Larisa A., Vladimir A. Silkin, Marina D. Kravchishina, Valeriy G. Yakubenko et Anna L. Chultsova. « Summer phytoplankton of the northern Barents Sea (75–80º N) ». Hydrosphere Еcology (Экология гидросферы), no 2(4) (2019) : 8–19. http://dx.doi.org/10.33624/2587-9367-2019-2(4)-8-19.
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The structure of the summer planktonic communities of the Northern part of the Barents sea in the first half of August 2017 were studied. In the sea-ice melting area, the average phytoplankton biomass producing upper 50-meter layer of water reached values levels of eutrophic waters (up to 2.1 g/m3). Phytoplankton was presented by diatoms of the genera Thalassiosira and Eucampia. Maximum biomass recorded at depths of 22–52 m, the absolute maximum biomass community (5,0 g/m3) marked on the horizon of 45 m (station 5558), located at the outlet of the deep trench Franz Victoria near the West coast of the archipelago Franz Josef Land. In ice-free waters, phytoplankton abundance was low, and the weighted average biomass (8.0 mg/m3 – 123.1 mg/m3) corresponded to oligotrophic waters and lower mesotrophic waters. In the upper layers of the water population abundance was dominated by small flagellates and picoplankton from, biomass – Arctic dinoflagellates (Gymnodinium spp.) and cold Atlantic complexes (Gyrodinium lachryma, Alexandrium tamarense, Dinophysis norvegica). The proportion of Atlantic species in phytoplankton reached 75%. The representatives of warm-water Atlantic complex (Emiliania huxleyi, Rhizosolenia hebetata f. semispina, Ceratium horridum) were recorded up to 80º N, as indicators of the penetration of warm Atlantic waters into the Arctic basin. The presence of oceanic Atlantic species as warm-water and cold systems in the high Arctic indicates the strengthening of processes of “atlantificacion” in the region.
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Lozier, M. Susan, et Laurie Sindlinger. « On the Source of Mediterranean Overflow Water Property Changes ». Journal of Physical Oceanography 39, no 8 (1 août 2009) : 1800–1817. http://dx.doi.org/10.1175/2009jpo4109.1.
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Abstract A recent study of the eastern North Atlantic detailed significant increases in the temperature and salinity of the Mediterranean Overflow Water (MOW) from 1950 to 2000. To examine the degree to which the source waters, which spill over the sill at the Strait of Gibraltar, could be responsible for these observations in the open Atlantic, a box model of water mass transformation by marginal seas was employed. Time series for the salinity of the inflowing North Atlantic surface waters, freshwater fluxes in the Mediterranean (evaporation and precipitation and river runoff), and the volumetric flow rates for the inflow and outflow across the Strait of Gibraltar were used to predict the salinity of the source waters to the North Atlantic from 1950 to 2000. Results from this calculation reveal that source water changes have minimal impact on MOW property changes on interannual and decadal time scales. It is suggested instead that circulation changes within the open Atlantic alter the advective–diffusive pathways of MOW such that property changes within the MOW reservoir are created.
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Sizov, A. A., T. M. Bayankina et V. L. Pososhkov. « FORMATION OF WINTER SURFACE TEMPERATURE ANOMALIES IN THE NORTH ATLANTIC IN DECADES OF NEGATIVE AND POSITIVE VALUES OF THE NORTH ATLANTIC OSCILLATION INDEX ». Доклады Российской академии наук. Науки о Земле 509, no 2 (1 février 2023) : 259–64. http://dx.doi.org/10.31857/s2686739722602824.
Texte intégralRésumé :
An analysis of the variability of the winter surface temperature anomaly in the North Atlantic in decades of negative and positive values of the North Atlantic Oscillation Index is presented. It was found that in the decade with negative values of the North Atlantic Oscillation Index, the slope waters of the Gulf Stream system and Labrador Current waters decrease the temperature of the Gulf Stream at the mixing zone on the Scotia Peninsula shelf and in the area of the quasistationary anticyclonic vortex to a maximum. In the decade with positive values of the North Atlantic Oscillation Index, the temperature of the slope waters is close to the climate. Taking into account the increased speed of the Gulf Stream in the years with positive values of the North Atlantic Oscillation Index, the spreading of the surface ocean temperature anomaly over the North Atlantic water area occurs for a shorter time than in the years with its negative values.
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Coolidge, M. « Great Waters : An Atlantic Passage ». Interdisciplinary Studies in Literature and Environment 11, no 1 (1 janvier 2004) : 242–43. http://dx.doi.org/10.1093/isle/11.1.242.
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Vermassen, Flor, Nanna Andreasen, David J. Wangner, Nicolas Thibault, Marit-Solveig Seidenkrantz, Rebecca Jackson, Sabine Schmidt, Kurt H. Kjær et Camilla S. Andresen. « A reconstruction of warm-water inflow to Upernavik Isstrøm since 1925 CE and its relation to glacier retreat ». Climate of the Past 15, no 3 (1 juillet 2019) : 1171–86. http://dx.doi.org/10.5194/cp-15-1171-2019.
Texte intégralRésumé :
Abstract. The mass loss from the Greenland Ice Sheet has increased over the past 2 decades. Marine-terminating glaciers contribute significantly to this mass loss due to increased melting and ice discharge. Periods of rapid retreat of these tidewater glaciers have been linked to the concurrent inflow of warm Atlantic-sourced waters. However, little is known about the variability of these Atlantic-derived waters within the fjords, due to a lack of multi-annual in situ measurements. Thus, to better understand the potential role of ocean warming on glacier retreat, reconstructions that characterize the variability of Atlantic water inflow to the fjords are required. Here, we investigate foraminiferal assemblages in a sediment core from Upernavik Fjord, West Greenland, in which the major ice stream Upernavik Isstrøm terminates. We conclude that the foraminiferal assemblage is predominantly controlled by changes in bottom water composition and provide a reconstruction of Atlantic water inflow to Upernavik Fjord, spanning the period 1925–2012. This reconstruction reveals peak Atlantic water influx during the 1930s and again after 2000, a pattern that is comparable to the Atlantic Multidecadal Oscillation (AMO). The comparison of these results to historical observations of front positions of Upernavik Isstrøm reveals that inflow of warm Atlantic-derived waters likely contributed to high retreat rates in the 1930s and after 2000. However, moderate retreat rates of Upernavik Isstrøm also prevailed in the 1960s and 1970s, showing that glacier retreat continued despite a reduced Atlantic water inflow, albeit at a lower rate. Considering the link between bottom water variability and the AMO in Upernavik Fjord, and the fact that a persistent negative phase of the AMO is expected for the next decade, Atlantic water inflow into the fjord may decrease in the coming decade, potentially minimizing or stabilizing the retreat of Upernavik Isstrøm during this time interval.
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Deloughrey, Elizabeth. « Heavy Waters : Waste and Atlantic Modernity ». PMLA/Publications of the Modern Language Association of America 125, no 3 (mai 2010) : 703–12. http://dx.doi.org/10.1632/pmla.2010.125.3.703.
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We cannot think of a time that is oceanlessOr of an ocean not littered with wastage—T. S. Eliot, “The Dry Salvages”A Poem that Renders the Sea as Pedagogical History, Lorna Goodison's “Arctic, Antarctic, Atlantic, Pacific, Indian Ocean” depicts Caribbean schoolchildren learning “the world's waters rolled into a chant.” After shivering through the “cold” Arctic and Antarctic, the class “suffered [a] sea change” in the destabilizing Atlantic, abandoning the terrestrial stability of their benches to enter an ocean in which only their voices orient them in time and space as they “call out across / the currents of hot air.” In fathoming what Derek Walcott has called “the sea [as] history,” their “small bodies” are “borrowed / by the long drowned” (Goodison). While colonial narratives of maritime expansion have long depicted the ocean as blank space to be traversed, these students enter Atlantic stasis, a place occupied by the wasted lives of Middle Passage modernity. This Atlantic is not aqua nullius, circumscribed and mapped by the student oceanographer, but rather a place where the haunting of the past overtakes the present subject. Édouard Glissant has described the Atlantic as a “beginning” for modernity, a space “whose time is marked by … balls and chains gone green” (Poetics 6): a sign of submarine history and its material decay. Thus, Atlantic modernity becomes legible through the sign of heavy water, an oceanic stasis that signals the dissolution of wasted lives. After the poem's irruptive consonance of the “bodies borrowed,” the vowels lengthen to mimic a “long drowned” history of the Atlantic, and the narrative is transformed. Reminding us that the Middle Passage “abyss is a tautology” that haunts ocean modernity (Glissant, Poetics 6), the poem traps the students (and readers) in the violent corporeal history of the Atlantic. Instead of moving on to the next ocean of the lesson, the class repeats the word “Atlantic, as if wooden pegs / were forced between our lips; Atlantic, as teacher's / strap whipped the rows on.” Only in the last two lines of the poem do we catch a glimpse of other oceans, trapped as we are in “learn[ing] this lesson: / Arctic, Antarctic, Atlantic, Pacific and then Indian.”
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Diansky, N. A., et V. A. Bagatinsky. « The thermohaline structure of the North Atlantic waters in different phases of the Atlantic multidecadal oscillation ». Известия Российской академии наук. Физика атмосферы и океана 55, no 6 (21 décembre 2019) : 157–70. http://dx.doi.org/10.31857/s0002-3515556157-170.
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The meridional structure of climatic trends and anomalies of potential temperature and salinity in the North Atlantic waters in different periods of the Atlantic Multidecadal Oscillation (AMO) in 19482017 are studied based on the EN4 and WOA2013 objective analyses data. An analysis of these different data sets allowed us to reveal almost identical patterns of variability of the thermohaline fields of the North Atlantic, which increases the reliability of the results. Long-term temperature and salinity trends simulated over the period 19482017 show that warming and salinization of water occur in the upper ~1 km layer of the North Atlantic. On the contrary, cooling and freshening of deep waters are observed, which is associated with the melting of the Greenland ice sheet, transport of fresher waters from the Arctic Ocean, and deepening of these cold and fresher waters into the deeper layers. Composite analysis of the zonally averaged temperature and salinity anomalies of the North Atlantic waters after removing the trends showed that in the warm AMO periods warming and salinization of waters are observed in the upper 1-km layer of the North Atlantic when compared to the cold periods based both on the EN4 and WOA2013 data. Below the 1-km layer, significant regions of cooling and freshening are observed; this distribution is more pronounced in the EN4 data. Analysis of the dynamics of zonally averaged temperature and salinity anomalies in the successive periods associated with the temporal variability of the AMO index revealed that these anomalies propagate along the zonally averaged meridional thermohaline circulation. To show this using the Institute of Numerical Mathematics Ocean Model (INMOM), the stream function of the Atlantic Meridional Overturning Circulation (AMOC) was simulated. It is shown that positive and negative anomalies of both temperature and salinity circulate along the water motion in the AMOC around its core, descending down into the deep ocean layers approximately at 60 N and ascending to the surface at 25 N, replacing each other with a period of about 60 years. It can be assumed that due to this process both the warm and cold phases of the AMO are formed.
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Burckel, Pierre, Claire Waelbroeck, Yiming Luo, Didier M. Roche, Sylvain Pichat, Samuel L. Jaccard, Jeanne Gherardi, Aline Govin, Jörg Lippold et François Thil. « Changes in the geometry and strength of the Atlantic meridional overturning circulation during the last glacial (20–50 ka) ». Climate of the Past 12, no 11 (8 novembre 2016) : 2061–75. http://dx.doi.org/10.5194/cp-12-2061-2016.
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Abstract. We reconstruct the geometry and strength of the Atlantic meridional overturning circulation during the Heinrich stadial 2 and three Greenland interstadials of the 20–50 ka period based on the comparison of new and published sedimentary 231Pa / 230Th data with simulated sedimentary 231Pa / 230Th. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present-day North Atlantic deep water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic bottom water (AABW). Our results further show that during Heinrich stadial 2, the deep Atlantic was probably directly affected by a southern-sourced water mass below 2500 m depth, while a slow, southward-flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500 m down to the equator.
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Voelker, A. H. L., T. Rodrigues, K. Billups, D. Oppo, J. McManus, R. Stein, J. Hefter et J. O. Grimalt. « Variations in mid-latitude North Atlantic surface water properties during the mid-Brunhes (MIS 9–14) and their implications for the thermohaline circulation ». Climate of the Past 6, no 4 (27 août 2010) : 531–52. http://dx.doi.org/10.5194/cp-6-531-2010.
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Abstract. Stable isotope and ice-rafted debris records from three core sites in the mid-latitude North Atlantic (IODP Site U1313, MD01-2446, MD03-2699) are combined with records of ODP Sites 1056/1058 and 980 to reconstruct hydrographic conditions during the middle Pleistocene spanning Marine Isotope Stages (MIS) 9–14 (300–540 ka). Core MD03-2699 is the first high-resolution mid-Brunhes record from the North Atlantic's eastern boundary upwelling system covering the complete MIS 11c interval and MIS 13. The array of sites reflect western and eastern basin boundary current as well as north to south transect sampling of subpolar and transitional water masses and allow the reconstruction of transport pathways in the upper limb of the North Atlantic's circulation. Hydrographic conditions in the surface and deep ocean during peak interglacial MIS 9 and 11 were similar among all the sites with relative stable conditions and confirm prolonged warmth during MIS 11c also for the mid-latitudes. Sea surface temperature (SST) reconstructions further reveal that in the mid-latitude North Atlantic MIS 11c is associated with two plateaus, the younger one of which is slightly warmer. Enhanced subsurface northward heat transport in the eastern boundary current system, especially during early MIS 11c, is denoted by the presence of tropical planktic foraminifer species and raises the question how strongly it impacted the Portuguese upwelling system. Deep water ventilation at the onset of MIS 11c significantly preceded surface water ventilation. Although MIS 13 was generally colder and more variable than the younger interglacials the surface water circulation scheme was the same. The greatest differences between the sites existed during the glacial inceptions and glacials. Then a north – south trending hydrographic front separated the nearshore and offshore waters off Portugal. While offshore waters originated from the North Atlantic Current as indicated by the similarities between the records of IODP Site U1313, ODP Site 980 and MD01-2446, nearshore waters as recorded in core MD03-2699 derived from the Azores Current and thus the subtropical gyre. Except for MIS 12, Azores Current influence seems to be related to eastern boundary system dynamics and not to changes in the Atlantic overturning circulation.
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Dulaquais, G., M. Boye, M. J. A. Rijkenberg et X. Carton. « Physical and remineralization processes govern the cobalt distribution in the deep western Atlantic Ocean ». Biogeosciences 11, no 6 (24 mars 2014) : 1561–80. http://dx.doi.org/10.5194/bg-11-1561-2014.
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Abstract. The distributions of the bio-essential trace element dissolved cobalt (DCo) and the apparent particulate Co (PCo) are presented along the GEOTRACES-A02 deep section from 64° N to 50° S in the western Atlantic Ocean (longest section of international GEOTRACES marine environment program). PCo was determined as the difference between total cobalt (TCo, unfiltered samples) and DCo. DCo concentrations ranged from 14.7 pM to 94.3 pM, and PCo concentrations from undetectable values to 18.8 pM. The lowest DCo concentrations were observed in the subtropical domains, and the highest in the low-oxygenated Atlantic Central Waters (ACW), which appears to be the major reservoir of DCo in the western Atlantic. In the Antarctic Bottom Waters, the enrichment in DCo with aging of the water mass can be related to suspension and redissolution of bottom sediments a well as diffusion of DCo from abyssal sediments. Mixing and dilution of deep water masses, rather than scavenging of DCo onto settling particles, generated the meridional decrease of DCo along the southward large-scale circulation in the deep western Atlantic. Furthermore, the apparent scavenged profile of DCo observed in the deep waters likely resulted from the persistence of relatively high concentrations in intermediate waters and low DCo concentrations in underlaying bottom waters. We suggest that the 2010 Icelandic volcanic eruption could have been a source of DCo that could have been transported into the core of the Northeast Atlantic Deep Waters. At intermediate depths, the high concentrations of DCo recorded in the ACW linearly correlated with the apparent utilization of oxygen (AOU), indicating that remineralization of DCo could be significant (representing up to 37% of the DCo present). Furthermore, the preferential remineralization of phosphate (P) compared to Co in these low-oxygenated waters suggests a decoupling between the deep cycles of P and Co. The vertical diffusion of DCo from the ACW appears to be a significant source of DCo into the surface waters of the equatorial domain. Summarizing, the dilution due to mixing processes rather than scavenging of DCo and the above-mentioned remineralization could be the two major pathways controlling the cycling of DCo into the intermediate and deep western Atlantic.
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Dulaquais, G., M. Boye, M. J. A. Rijkenberg et X. Carton. « Physical and remineralization processes govern the cobalt distribution in the deep western Atlantic ocean ». Biogeosciences Discussions 10, no 10 (16 octobre 2013) : 15951–6001. http://dx.doi.org/10.5194/bgd-10-15951-2013.
Texte intégralRésumé :
Abstract. The distributions of the bio-essential trace element dissolved Co (DCo) and the apparent particulate Co (PCo) are presented along the GEOTRACES-A02 deep section from 64° N to 50° S in the West Atlantic Ocean. PCo was determined as the difference between total cobalt (TCo, unfiltered samples) and DCo. DCo concentrations ranged from 14.7 pM to 94.3 pM, and PCo concentrations from undetectable values to 18.8 pM. The lowest DCo concentrations were observed in the subtropical domains, and the highest in the low-oxygenated Atlantic Central Waters (ACW) that appeared to be the major reservoir of DCo in the West Atlantic. In the Antarctic Bottom Waters, the enrichment in DCo with ageing of the water-mass can be related to suspension and redissolution of bottom sediments a well as diffusion of DCo from abyssal sediments. Mixing and dilution of deep water-masses, rather than scavenging of DCo onto settling particles, generated the meridional decrease of DCo along the southward large-scale circulation in the deep West Atlantic. Furthermore the apparent scavenged profile of DCo observed in the deep waters likely resulted from the persistence of relatively high concentrations in intermediate waters and low DCo concentrations in underlaying bottom waters. We suggested that the 2010 Icelandic volcanic eruption can be a source of DCo that could have been transported in the core of the North-East Atlantic Deep Waters. At intermediate depths, the high concentrations of DCo recorded in the ACW linearly correlated with the apparent utilization of oxygen (AOU), indicating that remineralization of DCo can be significant (representing up to 29% of the DCo present). Furthermore the preferential remineralization of phosphate (P) compared to Co in these low-oxygenated waters suggested a decoupling between the deep cycles of P and Co. The vertical diffusion of DCo from the ACW appeared to be a significant source of DCo into the surface waters of the equatorial domain. Summarizing the dilution and mixing processes rather than scavenging of DCo, and the remineralization can be the two major pathways controlling the cycling of DCo in the intermediate and deep West Atlantic.
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Garrison, Lance P., Anthony Martinez et Katherine Maze-Foley. « Habitat and abundance of cetaceans in Atlantic Ocean continental slope waters off the eastern USA ». J. Cetacean Res. Manage. 11, no 3 (14 février 2023) : 267–77. http://dx.doi.org/10.47536/jcrm.v11i3.606.
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This study quantifies the abundance and spatial distribution of the cetacean community occupying continental shelf edge and inner continental slope waters along the US southeast Atlantic coast. A shipboard visual line-transect survey was conducted between June and August of 2004 that included effort in waters >50m deep encompassing the shelf break and inner continental slope off the US east coast between 28°N and 38°N latitude. The abundance of nine cetacean taxa was estimated using line-transect distance analysis and an independent observer approach to correct for visibility bias. Canonical correspondence analysis was used to examine the spatial distribution of the cetaceans encountered during the survey as a function of surface temperature, surface salinity, surface fluorescence, bottom depth, and bottom slope. The abundance estimates for most species were much higher than those from a study of the area conducted in 1998. This is primarily due to increased coverage of the shelf-break region and correction for visibility bias. The multivariate analysis indicated four distinct groups of cetaceans that partitioned habitat as a function of salinity, depth, and a latitudinal gradient. These groups were associated with specific water masses and hydrographic features including mid-Atlantic shelf waters (Group I), the shelf break (Group II), mid-Atlantic slope waters (Group III), and south Atlantic slope water (Group IV). Areas where water masses converge such as the continental shelf break along the mid-Atlantic and near Cape Hatteras, North Carolina are therefore areas of both high diversity and density of cetaceans.
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Walczowski, W. « Frontal structures in the West Spitsbergen Current margins ». Ocean Science 9, no 6 (14 novembre 2013) : 957–75. http://dx.doi.org/10.5194/os-9-957-2013.
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Abstract. The structures of the hydrographic fronts separating the Atlantic-origin waters from ambient waters in the northern Nordic Seas are discussed. Flows of the western and eastern branches of the West Spitsbergen Current create the Atlantic domain borders and maintain these fronts. This work is based on previous research and on investigations carried out in the project DAMOCLES (Developing Arctic Modelling and Observational Capabilities for Long-term Environmental Studies). Most of the observational data were collected during the R/V Oceania cruises. The main focus of the paper is the western border of the Atlantic domain – the Arctic Front, alongfrontal and transfrontal transports, and the front instability and variability. The alongfrontal baroclinic jet streams were described as a significant source of the Atlantic Water and heat in the Nordic Seas. The baroclinic instability and advection of baroclinic eddies which occurs due to this instability were found to be the main transfrontal transport processes. Most of the Atlantic Water transported by the western branch recirculates west and southward. The eastern branch of the West Spitsbergen Current provides most of the Atlantic Water entering the Arctic Ocean. Both processes are very important for the Arctic and global thermohaline circulation.
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Ríos, Aida F., Laure Resplandy, Maribel I. García-Ibáñez, Noelia M. Fajar, Anton Velo, Xose A. Padin, Rik Wanninkhof, Reiner Steinfeldt, Gabriel Rosón et Fiz F. Pérez. « Decadal acidification in the water masses of the Atlantic Ocean ». Proceedings of the National Academy of Sciences 112, no 32 (27 juillet 2015) : 9950–55. http://dx.doi.org/10.1073/pnas.1504613112.
Texte intégralRésumé :
Global ocean acidification is caused primarily by the ocean’s uptake of CO2 as a consequence of increasing atmospheric CO2 levels. We present observations of the oceanic decrease in pH at the basin scale (50°S–36°N) for the Atlantic Ocean over two decades (1993–2013). Changes in pH associated with the uptake of anthropogenic CO2 (ΔpHCant) and with variations caused by biological activity and ocean circulation (ΔpHNat) are evaluated for different water masses. Output from an Institut Pierre Simon Laplace climate model is used to place the results into a longer-term perspective and to elucidate the mechanisms responsible for pH change. The largest decreases in pH (∆pH) were observed in central, mode, and intermediate waters, with a maximum ΔpH value in South Atlantic Central Waters of −0.042 ± 0.003. The ΔpH trended toward zero in deep and bottom waters. Observations and model results show that pH changes generally are dominated by the anthropogenic component, which accounts for rates between −0.0015 and −0.0020/y in the central waters. The anthropogenic and natural components are of the same order of magnitude and reinforce one another in mode and intermediate waters over the time period. Large negative ΔpHNat values observed in mode and intermediate waters are driven primarily by changes in CO2 content and are consistent with (i) a poleward shift of the formation region during the positive phase of the Southern Annular Mode in the South Atlantic and (ii) an increase in the rate of the water mass formation in the North Atlantic.
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Shadwick, E. H., T. Papakyriakou, A. E. F. Prowe, D. Leong, S. A. Moore et H. Thomas. « Carbon cycling in the Arctic Archipelago : the export of Pacific carbon to the North Atlantic ». Biogeosciences Discussions 6, no 1 (16 janvier 2009) : 971–94. http://dx.doi.org/10.5194/bgd-6-971-2009.
Texte intégralRésumé :
Abstract. The Arctic Ocean is expected to be disproportionately sensitive to climatic changes, and is thought to be an area where such changes might be detected. The Arctic hydrological cycle is influenced by: runoff and precipitation, sea ice formation/melting, and the inflow of saline waters from Bering and Fram Straits and the Barents Sea Shelf. Pacific water is recognizable as intermediate salinity water, with high concentrations of dissolved inorganic carbon (DIC), flowing from the Arctic Ocean to the North Atlantic via the Canadian Arctic Archipelago. We present DIC data from an east-west section through the Archipelago, as part of the Canadian International Polar Year initiatives. The fractions of Pacific and Arctic Ocean waters leaving the Archipelago and entering Baffin Bay, and subsequently the North Atlantic, are computed. The eastward transport of carbon from the Pacific, via the Arctic, to the North Atlantic is estimated. Altered mixing ratios of Pacific and freshwater in the Arctic Ocean have been recorded in recent decades. Any climatically driven alterations in the composition of waters leaving the Arctic Archipelago may have implications for anthropogenic CO2 uptake, and hence ocean acidification, in the subpolar and temperate North Atlantic.
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Haines, Keith, et Chris Old. « Diagnosing Natural Variability of North Atlantic Water Masses in HadCM3 ». Journal of Climate 18, no 12 (15 juin 2005) : 1925–41. http://dx.doi.org/10.1175/jcli3348.1.
Texte intégralRésumé :
Abstract A study of thermally driven water mass transformations over 100 yr in the ocean component of the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) is presented. The processes of surface-forced transformations, subduction and mixing, both above and below the winter mixed layer base, are quantified. Subtropical Mode Waters are formed by surface heat fluxes and subducted at more or less the same rate. However, Labrador Seawater and Nordic Seawater classes (the other main subduction classes) are primarily formed by mixing within the mixed layer with very little formation directly from surface heat fluxes. The Subpolar Mode Water classes are dominated by net obduction of water back into the mixed layer from below. Subtropical Mode Water (18°C) variability shows a cycle of formation by surface fluxes, subduction ∼2 yr later, followed by mixing with warmer waters below the winter mixed layer base during the next 3 yr, and finally obduction back into the mixed layer at 21°C, ∼5 yr after the original formation. Surface transformation of Subpolar Mode Waters, ∼12°C, are led by surface transformations of warmer waters by up to 5 yr as water is transferred from the subtropical gyre. They are also led by obduction variability from below the mixed layer, by ∼2 yr. The variability of obduction in Subpolar Mode Waters also appears to be preceded, by 3–5 yr, by variability in subduction of Labrador Sea Waters at ∼6°C. This supports a mechanism in which southward-propagating Labrador seawater anomalies below the subpolar gyre can influence the upper water circulation and obduction into the mixed layer.
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Moore, Robert M. « Trichloroethylene and tetrachloroethylene in Atlantic waters ». Journal of Geophysical Research : Oceans 106, no C11 (15 novembre 2001) : 27135–43. http://dx.doi.org/10.1029/2000jc000374.
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Arbic, Brian K., et W. Brechner Owens. « Climatic Warming of Atlantic Intermediate Waters* ». Journal of Climate 14, no 20 (octobre 2001) : 4091–108. http://dx.doi.org/10.1175/1520-0442(2001)014<4091:cwoaiw>2.0.co;2.
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Bovery, Caitlin M., et Jeanette Wyneken. « Sea Turtles in Florida's Atlantic Waters ». Marine Fisheries Review 75, no 3 (6 décembre 2013) : 1–12. http://dx.doi.org/10.7755/mfr.75.3.1.
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Savenko, A. V., V. S. Savenko et A. N. Novigatsky. « FLUORINE IN THE NORTH ATLANTIC WATERS ». Lomonosov Geography Journal 78, no 1 (2023) (7 juillet 2023) : 143–47. http://dx.doi.org/10.55959/msu0579-9414-5-2023-1-143-147.
Texte intégralRésumé :
New data on the fluorine content in North Atlantic waters was obtained by the method of direct potenti-ometry with a fluoride ion-selective electrode. The measured fluorine concentration was equal to 1,27 0,03 mg/kg at F/Cl mass ratio of (6,59 0,11) · 10-5, which closely corresponds to the normal fluorine content in seawater. The totality of available data on the F/Cl ratio in different areas of the World Ocean suggests rather low variability of the fluorine content in seawater salts.
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Walczowski, W. « Frontal structures in the West Spitsbergen Current margins ». Ocean Science Discussions 10, no 4 (2 juillet 2013) : 985–1030. http://dx.doi.org/10.5194/osd-10-985-2013.
Texte intégralRésumé :
Abstract. The structures of the hydrographic fronts separating the Atlantic origin waters from ambient waters in the northern Nordic Seas are discussed. Flows of the western and eastern branches of the West Spitsbergen Current create the Atlantic domain borders and maintain these fronts. The work is based on previous research and on investigations in the project DAMOCLES (Developing Arctic Modeling and Observational Capabilities for Long-term Environmental Studies). Most of the observational data were collected during the R/V Oceania cruises. The main focus of the paper is put on the western border of the Atlantic domain – the Arctic Front, along- and transfrontal transports, the front instability and variability. The baroclinic instability and advection of baroclinic eddies which occurs due to this instability were found as the main transfrontal transport processes. Most of the Atlantic Water transported by the western branch recirculates west and southward. The eastern branch of the West Spitsbergen Current provides most of the Atlantic Water entering the Arctic Ocean. Both processes are very important for the Arctic and global Thermohaline Circulation.
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Deng, Feifei, Gideon M. Henderson, Maxi Castrillejo, Fiz F. Perez et Reiner Steinfeldt. « Evolution of <sup>231</sup>Pa and <sup>230</sup>Th in overflow waters of the North Atlantic ». Biogeosciences 15, no 23 (10 décembre 2018) : 7299–313. http://dx.doi.org/10.5194/bg-15-7299-2018.
Texte intégralRésumé :
Abstract. Many palaeoceanographic studies have sought to use the 231Pa∕230Th ratio as a proxy for deep ocean circulation rates in the North Atlantic. As of yet, however, no study has fully assessed the concentration of, or controls on, 230Th and 231Pa in waters immediately following ventilation at the start of Atlantic meridional overturning. To that end, full water-column 231Pa and 230Th concentrations were measured along the GEOVIDE section, sampling a range of young North Atlantic deep waters. 230Th and 231Pa concentrations in the water column are lower than those observed further south in the Atlantic, ranging between 0.06 and 12.01 µBq kg−1 and between 0.37 and 4.80 µBq kg−1, respectively. Both 230Th and 231Pa profiles generally increase with water depth from surface to deep water, followed by decrease near the seafloor, with this feature most pronounced in the Labrador Sea (LA Sea) and Irminger Sea (IR Sea). Assessing this dataset using extended optimum multi-parameter (eOMP) analysis and CFC-based water mass age indicates that the low values of 230Th and 231Pa in water near the seafloor of the LA Sea and IR Sea are related to the young waters present in those regions. The importance of water age is confirmed for 230Th by a strong correlation between 230Th and water mass age (though this relationship with age is less clear for 231Pa and the 231Pa∕230Th ratio). Scavenged 231Pa and 230Th were estimated and compared to their potential concentrations in the water column due to ingrowth. This calculation indicates that more 230Th is scavenged (∼80 %) than 231Pa (∼40 %), consistent with the relatively higher particle reactivity of 230Th. Enhanced scavenging for both nuclides is demonstrated near the seafloor in young overflow waters. Calculation of the meridional transport of 230Th and 231Pa with this new GEOVIDE dataset enables a complete budget for 230Th and 231Pa for the North Atlantic. Results suggest that net transport southward of 230Th and 231Pa across GEOVIDE is smaller than transport further south in the Atlantic, and indicate that the flux to sediment in the North Atlantic is equivalent to 96 % of the production of 230Th and 74 % of the production for 231Pa. This result confirms a significantly higher advective loss of 231Pa to the south relative to 230Th and supports the use of 231Pa∕230Th to assess meridional transport at a basin scale.
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MADEIRA, PATRÍCIA, ANDREAS KROH, RICARDO CORDEIRO, ANTÓNIO M. DE FRIAS MARTINS et SÉRGIO P. ÁVILA. « The Echinoderm Fauna of the Azores (NE Atlantic Ocean) ». Zootaxa 4639, no 1 (19 juillet 2019) : 1–231. http://dx.doi.org/10.11646/zootaxa.4639.1.1.
Texte intégralRésumé :
In more than 150 years of research in the waters surrounding the Azores, several publications on the fauna of echinoderms of the archipelago have been produced, in the form of papers, notes, reports, reviews, and monographs. This work attempts to summarize the present knowledge on this marine group in the Azorean exclusive economic zone (i.e., waters within 200 nautical miles of the archipelago’s shores). A short review of the history of the species’ taxonomy is given, with key references, geographical distribution, ecology, additional notes and, when possible, figures. We herein report 172 species of echinoderms (6 crinoids, 55 ophiuroids, 45 asteroids, 36 holothurians, and 30 echinoids) from the Azores Archipelago, most of them inhabiting deep waters (>200 m). Only 29 shallow-water species were recorded locally (≤50 m depth). In general, the echinoderm species present in the Azores are characterized by a wide geographical distribution in the Atlantic Ocean. Only nine taxa (all deep-water species, >840 m) appear to be restricted to the Azorean waters. Overall, the knowledge of the echinoderm fauna of the Azores is out-dated, with many species last collected in the archipelago over 100 years ago. A recent interest in the Azorean Mid-Atlantic waters has brought oceanographic cruises back to the archipelago, thus providing new opportunities for the renewal of 150 years of echinoderm studies in the area.
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Vázquez-Rodríguez, M., F. F. Pérez, A. Velo, A. F. Ríos et H. Mercier. « Observed acidification trends in North Atlantic water masses ». Biogeosciences 9, no 12 (18 décembre 2012) : 5217–30. http://dx.doi.org/10.5194/bg-9-5217-2012.
Texte intégralRésumé :
Abstract. The lack of observational pH data has made it difficult to assess recent rates of ocean acidification, particularly in the high latitudes. Here we present a time series that spans over 27 yr (1981–2008) of high-quality carbon system measurements in the North Atlantic, which comprises fourteen cruises and covers the important water mass formation areas of the Irminger and Iceland Basins. We provide direct quantification of acidification rates in upper and intermediate North Atlantic waters. The highest rates were associated with surface waters and with Labrador Sea Water (LSW). The Subarctic Intermediate and Subpolar Mode Waters (SAIW and SPMW) showed acidification rates of −0.0019 ± 0.0001 and −0.0012 ± 0.0002 yr−1, respectively. The deep convection activity in the North Atlantic Subpolar Gyre injects surface waters loaded with anthropogenic CO2 into lower layers, provoking the remarkable acidification rate observed for LSW in the Iceland Basin (−0.0016 ± 0.0002 yr−1). An extrapolation of the observed linear acidification trends suggests that the pH of LSW could drop 0.45 units with respect to pre-industrial levels by the time atmospheric CO2 concentrations reach ~775 ppm. Under circulation conditions and evolution of CO2 emission rates similar to those of the last three decades, by the time atmospheric CO2 reaches 550 ppm, an aragonite undersaturation state could be reached in the cLSW of the Iceland Basin, earlier than surface SPMW.
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Deremble, Bruno, et W. K. Dewar. « Volume and Potential Vorticity Budgets of Eighteen Degree Water ». Journal of Physical Oceanography 43, no 11 (1 novembre 2013) : 2309–21. http://dx.doi.org/10.1175/jpo-d-13-052.1.
Texte intégralRésumé :
Abstract Mode waters are a distinctive baroclinic feature of the World Ocean characterized by relatively weak vertical stratification. They correspond dynamically to low potential vorticity (PV). In the North Atlantic subtropical gyre, the mode waters have become known as Eighteen Degree Water. Their dynamics involves air–sea interaction, diapycnal and isopycnal mixing, and subduction. Understanding mode water dynamics is therefore both challenging and important since it connects several aspects of the ocean circulation. Mass and PV budget of the mode water's core, evaluated in a realistic primitive equation North Atlantic model, are used to characterize mode water maintenance. It is shown that the surface PV flux has very little impact on mode water; the surface buoyancy flux in combination with eddy mass flux is the most important control on mode water structure. A mean PV formalism is used to show that the PV and water-mass formation budgets are intrinsically linked. A decomposition of the budget demonstrates the role of the mean PV field in permitting the eddy mass flux to discharge the net formation to the surrounding fluid.
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Sutton, Jill N., Gregory F. de Souza, Maribel I. García-Ibáñez et Christina L. De La Rocha. « The silicon stable isotope distribution along the GEOVIDE section (GEOTRACES GA-01) of the North Atlantic Ocean ». Biogeosciences 15, no 18 (21 septembre 2018) : 5663–76. http://dx.doi.org/10.5194/bg-15-5663-2018.
Texte intégralRésumé :
Abstract. The stable isotope composition of dissolved silicon in seawater (δ30SiDSi) was examined at 10 stations along the GEOVIDE section (GEOTRACES GA-01), spanning the North Atlantic Ocean (40–60∘ N) and Labrador Sea. Variations in δ30SiDSi below 500 m were closely tied to the distribution of water masses. Higher δ30SiDSi values are associated with intermediate and deep water masses of northern Atlantic or Arctic Ocean origin, whilst lower δ30SiDSi values are associated with DSi-rich waters sourced ultimately from the Southern Ocean. Correspondingly, the lowest δ30SiDSi values were observed in the deep and abyssal eastern North Atlantic, where dense southern-sourced waters dominate. The extent to which the spreading of water masses influences the δ30SiDSi distribution is marked clearly by Labrador Sea Water (LSW), whose high δ30SiDSi signature is visible not only within its region of formation within the Labrador and Irminger seas, but also throughout the mid-depth western and eastern North Atlantic Ocean. Both δ30SiDSi and hydrographic parameters document the circulation of LSW into the eastern North Atlantic, where it overlies southern-sourced Lower Deep Water. The GEOVIDE δ30SiDSi distribution thus provides a clear view of the direct interaction between subpolar/polar water masses of northern and southern origin, and allow examination of the extent to which these far-field signals influence the local δ30SiDSi distribution.
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Levesque, Juan C., Christian Hager, Eric Diaddorio et R. Jason Dickey. « Commercial fishing gear modifications to reduce interactions between Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) and the southern flounder (Paralichthys lethostigma) fishery in North Carolina (USA) ». PeerJ 4 (20 juillet 2016) : e2192. http://dx.doi.org/10.7717/peerj.2192.
Texte intégralRésumé :
Bycatch of protected species in commercial fishing operations is a primary concern to fishery managers because it threatens the conservation, protection, and recovery of fragile species, such as the Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus). One potential solution to reduce the risk associated with commercial fishing operations is to design commercial fishing gear that is more selective in terms of interactions between Atlantic sturgeon and commercial fisheries. Given this conservation and management need, the overarching goal was to reduce Atlantic sturgeon fishery interactions and maintain southern flounder (Paralichthys lethostigma) catch in North Carolina. The specific objectives of this study were to design and evaluate the effectiveness of a modified gillnet. Overall, the results proved that lowering the profile and amount of webbing had a beneficial impact at reducing Atlantic sturgeon incidental encounters and bycatch. The modified gillnet reduced bycatch and Atlantic sturgeon encounters by 39.6% and 60.9%, respectively. Our design entangled 51.6% fewer southern flounder, which corresponded to a 48.9% reduction in total weight; the modified gear entangled slightly larger southern flounder than the control gear. Our findings showed the number of Atlantic sturgeon encounters was positively associated with mean water depth, with more Atlantic sturgeon encountered in deeper (5.1–6.3 m) than shallower waters; 75% were encountered at depths between 4.6 and 6.1 m. Most southern flounder (n= 518, 39.7%) were taken at a water depth between 3.76 and 5.0 m. This observation suggests that southern flounder prefer slightly shallower waters than Atlantic sturgeon.
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Eduardo, Leandro Nolé, Bárbara Teixeira Villarins, Julia Rodrigues Martins, Flávia Lucena-Frédou, Thierry Frédou, Alex Souza Lira, Paulo Eurico Travassos, Arnaud Bertrand et Michael Maia Mincarone. « Deep-sea oceanic basslets (Perciformes, Howellidae) from Brazil : new records and range extensions ». Check List 15, no 6 (1 novembre 2019) : 965–71. http://dx.doi.org/10.15560/15.6.965.
Texte intégralRésumé :
This study reports the occurrence of the oceanic basslet (Howellidae) in Brazilian waters. Bathysphyraenops simplex Parr, 1933, a rare species with a worldwide distribution, is recorded for the first time in Brazilian waters, based on three specimens collected off Rocas Atoll and Rio Grande do Norte. Howella atlantica Post & Quéro, 1991, known from the western and eastern Atlantic Ocean (64°N to 21°S), including waters around the Trindade Island, is reported off Rio Grande do Norte, Pernambuco, Rocas Atoll, and the Fernando de Noronha Archipelago. In addition, specimens previously reported in the literature as Howella brodie Ogilby, 1899 are reidentified as H. atlantica, extending the known distribution of this species to northeastern and southeastern Brazil. Measurements and counts for all specimens examined are provided.
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Olafsson, Jon, Solveig R. Olafsdottir, Taro Takahashi, Magnus Danielsen et Thorarinn S. Arnarson. « Enhancement of the North Atlantic CO<sub>2</sub> ; sink by Arctic Waters ». Biogeosciences 18, no 5 (10 mars 2021) : 1689–701. http://dx.doi.org/10.5194/bg-18-1689-2021.
Texte intégralRésumé :
Abstract. The North Atlantic north of 50∘ N is one of the most intense ocean sink areas for atmospheric CO2 considering the flux per unit area, 0.27 Pg-C yr−1, equivalent to −2.5 mol C m−2 yr−1. The northwest Atlantic Ocean is a region with high anthropogenic carbon inventories. This is on account of processes which sustain CO2 air–sea fluxes, in particular strong seasonal winds, ocean heat loss, deep convective mixing, and CO2 drawdown by primary production. The region is in the northern limb of the global thermohaline circulation, a path for the long-term deep-sea sequestration of carbon dioxide. The surface water masses in the North Atlantic are of contrasting origins and character, with the northward-flowing North Atlantic Drift, a Gulf Stream offspring, on the one hand and on the other hand the cold southward-moving low-salinity Polar and Arctic waters with signatures from Arctic freshwater sources. We have studied by observation the CO2 air–sea flux of the relevant water masses in the vicinity of Iceland in all seasons and in different years. Here we show that the highest ocean CO2 influx is to the Arctic and Polar waters, respectively, -3.8±0.4 and -4.4±0.3 mol C m−2 yr−1. These waters are CO2 undersaturated in all seasons. The Atlantic Water is a weak or neutral sink, near CO2 saturation, after poleward drift from subtropical latitudes. These characteristics of the three water masses are confirmed by data from observations covering 30 years. We relate the Polar Water and Arctic Water persistent undersaturation and CO2 influx to the excess alkalinity derived from Arctic sources. Carbonate chemistry equilibrium calculations clearly indicate that the excess alkalinity may support at least 0.058 Pg-C yr−1, a significant portion of the North Atlantic CO2 sink. The Arctic contribution to the North Atlantic CO2 sink which we reveal was previously unrecognized. However, we point out that there are gaps and conflicts in the knowledge about the Arctic alkalinity and carbonate budgets and that future trends in the North Atlantic CO2 sink are connected to developments in the rapidly warming and changing Arctic. The results we present need to be taken into consideration for the following question: will the North Atlantic continue to absorb CO2 in the future as it has in the past?
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Paterne, Martine, Nathalie Feuillet, Guy Cabioch, Elsa Cortijo, Dominique Blamart, Jennifer Weill-Accardo, Lucile Bonneau, Christophe Colin, Eric Douville et Edwige Pons-Branchu. « Reservoir Ages in the Western Tropical North Atlantic from One Coral off Martinique Island (Lesser Antilles) ». Radiocarbon 60, no 2 (avril 2018) : 639–52. http://dx.doi.org/10.1017/rdc.2017.118.
Texte intégralRésumé :
AbstractSea surface reservoir ages (R) are reported from radiocarbon (14C) measurements of the annual growth bands of coral Siderastrea siderea collected on the Atlantic coast off Martinique Island, in the Lesser Antilles volcanic arc. Mean values of R are similar between 1835 and 1845 during pre-anthropogenic times at 385±30 yr and between 1895 and 1905 at 382±20 yr when there was a huge eruption from the Montagne Pelée volcano in 1902–1903. Limited 14C aging of sea surface (~40 yr) may be due to enhanced volcanic activity. Variability of R is slightly greater during 1835–1845 than during 1895–1905. It is linked to a moderate increase of ∆14C of 5‰, strengthened by a clear increase of δ18O of 0.4‰. This is attributed to a decrease of the northward advection of the South Atlantic Waters into the western tropical North Atlantic and Caribbean Sea and relative enhanced westward flux of the tropical North Atlantic surface waters, the southern waters having lower values of 14C and δ18O than the North Atlantic ones. From 1835 to 1845, the fraction of the South Atlantic Waters transported up to Martinique Island was reduced from 25% to 15%.
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Lozier, M. S., F. Li, S. Bacon, F. Bahr, A. S. Bower, S. A. Cunningham, M. F. de Jong et al. « A sea change in our view of overturning in the subpolar North Atlantic ». Science 363, no 6426 (31 janvier 2019) : 516–21. http://dx.doi.org/10.1126/science.aau6592.
Texte intégralRésumé :
To provide an observational basis for the Intergovernmental Panel on Climate Change projections of a slowing Atlantic meridional overturning circulation (MOC) in the 21st century, the Overturning in the Subpolar North Atlantic Program (OSNAP) observing system was launched in the summer of 2014. The first 21-month record reveals a highly variable overturning circulation responsible for the majority of the heat and freshwater transport across the OSNAP line. In a departure from the prevailing view that changes in deep water formation in the Labrador Sea dominate MOC variability, these results suggest that the conversion of warm, salty, shallow Atlantic waters into colder, fresher, deep waters that move southward in the Irminger and Iceland basins is largely responsible for overturning and its variability in the subpolar basin.
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Bryden, H. L., B. A. King, G. D. McCarthy et E. L. McDonagh. « Impact of a 30% reduction in Atlantic meridional overturning during 2009–2010 ». Ocean Science 10, no 4 (6 août 2014) : 683–91. http://dx.doi.org/10.5194/os-10-683-2014.
Texte intégralRésumé :
Abstract. The Atlantic meridional overturning circulation comprises warm upper waters flowing northward, becoming colder and denser until they form deep water in the Labrador and Nordic Seas that then returns southward through the North and South Atlantic. The ocean heat transport associated with this circulation is 1.3 PW, accounting for 25% of the maximum combined atmosphere–ocean heat transport necessary to balance the Earth's radiation budget. We have been monitoring the circulation at 25° N since 2004. A 30% slowdown in the circulation for 14 months during 2009–2010 reduced northward ocean heat transport across 25° N by 0.4 PW and resulted in colder upper ocean waters north of 25° N and warmer waters south of 25° N. The spatial pattern of upper ocean temperature anomalies helped push the wintertime circulation 2010–2011 into record-low negative NAO (North Atlantic Oscillation) conditions with accompanying severe winter conditions over northwestern Europe. The warmer temperatures south of 25° N contributed to the high intensity hurricane season in summer 2010.
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Meredith, Michael P., Loïc Jullion, Peter J. Brown, Alberto C. Naveira Garabato et Matthew P. Couldrey. « Dense waters of the Weddell and Scotia Seas : recent changes in properties and circulation ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 372, no 2019 (13 juillet 2014) : 20130041. http://dx.doi.org/10.1098/rsta.2013.0041.
Texte intégralRésumé :
The densest waters in the Atlantic overturning circulation are sourced at the periphery of Antarctica, especially the Weddell Sea, and flow northward via routes that involve crossing the complex bathymetry of the Scotia Arc. Recent observations of significant warming of these waters along much of the length of the Atlantic have highlighted the need to identify and understand the time-varying formation and export processes, and the controls on their properties and flows. Here, we review recent developments in understanding of the processes that control the changing flux of water through the main export route from the Weddell Sea into the Scotia Sea, and the transformations of the waters within the Scotia Sea and environs. We also present a synopsis of recent findings that relate to the climatic change of dense water properties within the Weddell Sea itself, in the context of known Atlantic-scale changes. Among the most significant findings are the discovery that the warming of waters exported from the Weddell Sea has been accompanied by a significant freshening, and that the episodic nature of the overflow into the Scotia Sea is markedly wind-controlled and can lead to significantly enhanced abyssal stratification. Key areas for focusing future research effort are outlined.
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Bastien, G., A. Barkley, J. Chappus, V. Heath, S. Popov, R. Smith, T. Tran et al. « Inconspicuous, recovering, or northward shift : status and management of the white shark (Carcharodon carcharias) in Atlantic Canada ». Canadian Journal of Fisheries and Aquatic Sciences 77, no 10 (octobre 2020) : 1666–77. http://dx.doi.org/10.1139/cjfas-2020-0055.
Texte intégralRésumé :
Although white sharks (Carcharodon carcharias) have been considered rare in Atlantic Canada waters, recent sighting records indicate a potentially increasing presence. We combine historical to present sighting data with satellite telemetry tracks of large juvenile and adult white sharks tagged in US (n = 9) and Atlantic Canada waters (n = 17) to show seasonal white shark presence and distribution in Atlantic Canada, returns by individuals over multiple years, and high site fidelity to the region. Telemetry data indicate that white sharks are a more common and consistent occurrence in Canadian waters than previously thought, presenting two potential scenarios: (i) tagging technology is revealing white shark presence that was historically cryptic and (or) (ii) a northward range expansion of white sharks in the Northwest Atlantic, potentially due to climate change, population recovery, and (or) increasing pinniped prey. Given combined sighting and telemetry data indicate a current need for proactive management of white sharks in Atlantic Canada waters, we propose the basis for a management action plan, addressing conservation priorities, management goals, and research incentives while considering the potential for human–shark interactions.
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Kashgarian, Michaele, et Noriyuki Tanaka. « Antarctic intermediate water intrusion into South Atlantic Bight shelf waters ». Continental Shelf Research 11, no 2 (février 1991) : 197–201. http://dx.doi.org/10.1016/0278-4343(91)90062-b.
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Guelpen, Louis Van. « Hookear sculpins (genus Artediellus) of the North American Atlantic : taxonomy, morphological variability, distribution, and aspects of life history ». Canadian Journal of Zoology 64, no 3 (1 mars 1986) : 677–90. http://dx.doi.org/10.1139/z86-100.
Texte intégralRésumé :
Difficulty in identifying the two nominal species of hookear sculpins (genus Artediellus) from the North American Atlantic has led to confusion in their taxonomy and reported distributions. The species were found to be separable using nine meristic and six morphological characters, as well as collection locality. Sexual dimorphism and clinal geographic variation occurred in several characters of both species. The known northern limit of A. atlanticus (the Atlantic hookear) in North America was extended to southeast Baffin Island, also the northern limit for A. uncinatus (the snowflake hookear). The southern limits were off Cape Cod for A. atlanticus and northern Nova Scotia for A. uncinatus. Artediellus uncinatus inhabited a shallower depth range (13–183 m) than A. atlanticus (0–384 m), indicating at least partial ecological separation. The latter species had a positive size–depth relationship, with the largest fish inhabiting the deep northern waters. Artediellus atlanticus seemed to prefer softer bottom sediments, while A. uncinatus showed no preference. Overall, sex ratios were similar (1.29 males to females in A. atlanticus and 1.12 in A. uncinatus). In North American waters, A. atlanticus spawns from approximately May to November and A. uncinatus during summer. Both nominal species warrant full specific status; however, subspecies designations appear unfounded.
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Bibby, T. S., et C. M. Moore. « Silicate:nitrate ratios of upwelled waters control the phytoplankton community sustained by mesoscale eddies in sub-tropical North Atlantic and Pacific ». Biogeosciences 8, no 3 (14 mars 2011) : 657–66. http://dx.doi.org/10.5194/bg-8-657-2011.
Texte intégralRésumé :
Abstract. Mesoscale eddies in sub-tropical gyres physically perturb the water column and can introduce macronutrients to the euphotic zone, stimulating a biological response in which phytoplankton communities can become dominated by large phytoplankton. Mesoscale eddies may therefore be important in driving export in oligotrophic regions of the modern ocean. However, the character and magnitude of the biological response sustained by eddies is variable. Here we present data from mesoscale eddies in the Sargasso Sea (Atlantic) and the waters off Hawai'i (Pacific), alongside mesoscale events that affected the Bermuda Atlantic Time-Series Study (BATS) over the past decade. From this analysis, we suggest that the phytoplankton community structure sustained by mesoscale eddies is predetermined by the relative abundance of silicate over nitrate (Si*) in the upwelled waters. We present data that demonstrate that mode-water eddies (MWE) in the Sargasso Sea upwell locally formed waters with relatively high Si* to the euphotic zone, and that cyclonic eddies in the Sargasso Sea introduce waters with relatively low Si*, a signature that originated in the iron-limited Southern Ocean. We propose that this phenomenon can explain the observed dominance of the phytoplankton community by large-diatom species in MWE and by small prokaryotic phytoplankton in cyclonic features. In contrast to the Atlantic, North Pacific Intermediate Water (NPIW) with high Si* may influence the cyclonic eddies in waters off Hawai'i, which also appear capable of sustaining diatom populations. These observations suggest that the structure of phytoplankton communities sustained by eddies may be related to the chemical composition of the upwelled waters in addition to the physical nature of the eddy.
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Sentyabov, E. V. « Estimation of long-term changes in thermal conditions and distribution of Atlantic and Subarctic water in the XXI Century in the Norwegian Sea on area surveys data ». Trudy VNIRO 192 (15 août 2023) : 162–71. http://dx.doi.org/10.36038/2307-3497-2023-192-162-171.
Texte intégralRésumé :
Purpose of the work: assessing the spatial and temporal variability of thermal conditions in waters of various origins in the Norwegian Sea in the first decades of the 21st century. Materials: oceanographic data collected during the International Ecosystem Surveys in the Norwegian Sea in 2000–2021. Methods used: comparative data analysis, descriptive statistics methods, correlation analysis. Results: the “boxes”, temperature in which most fully describes the change in the temperature of the Atlantic and Subarctic waters of the Norwegian Sea, were identified. This is confirmed by the high correlation coefficients of temperature in the “boxes” with the water temperature over a wide area of distribution of waters of various origins. The interannual temperature variability in the “boxes” was studied with the separation of warm and cold periods. An assessment of the interannual variability of the distribution boundaries of the Atlantic and subarctic waters is made by the position of isotherms at different horizons. A statistically significant relationship is shown between changes in the temperature of Atlantic and Subarctic waters according to the “boxes” data and changes in the boundaries of the distribution of water masses and the position of the frontal zone between them. Practical significance: the results of the analysis of in situ data from annual areal surveys make it possible to estimate the interannual variability of the thermal state of waters of various origins in the Norwegian Sea in the absence of standard sections and can be used to predict the distribution of pelagic fish in the sea area depending on oceanographic conditions.
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Tarkhanova, Marina A., et Elena N. Golubeva. « CHANGES IN THE HYDROLOGICAL CHARACTERISTICS OF THE ARCTIC OCEAN UNDER THE INFLUENCE OF INCREASING RIVER RUNOFF ». Interexpo GEO-Siberia 4, no 1 (21 mai 2021) : 210–16. http://dx.doi.org/10.33764/2618-981x-2021-4-1-210-216.
Texte intégralRésumé :
The paper considers issues related to the influence of increased Arctic river runoff on the formation of the thermohaline structure of waters outside the Arctic shelf and, in particular, on the variability of heat content of the deep Arctic Ocean. The study is carried out using the three-dimensional numerical model of the ocean and sea ice SibCIOM and atmospheric reanalysis data NCEP/NCAR. Numerical simulation results showed that increased flow of Arctic rivers contributes to the stability of water stratification outside the shelf areas, which reduces the depth of autumn-winter mixing and allows Atlantic waters spreading along the continental slope to retain their heat. This is evidenced by an increase in the heat content of the upper 200 m layer waters of the eastern Eurasian basin and the rise of the Atlantic water layer upper boundary in this region.
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Govin, A., P. Braconnot, E. Capron, E. Cortijo, J. C. Duplessy, E. Jansen, L. Labeyrie et al. « Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial ». Climate of the Past 8, no 2 (14 mars 2012) : 483–507. http://dx.doi.org/10.5194/cp-8-483-2012.
Texte intégralRésumé :
Abstract. Although the Last Interglacial (LIG) is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It is associated with (1) colder and fresher surface-water conditions in the North Atlantic, Labrador and Norwegian Seas, and (2) a weaker ventilation of North Atlantic deep waters during the early LIG (129–125 ka) compared to the late LIG. Results from an ocean-atmosphere coupled model with insolation as a sole forcing for three key periods of the LIG show warmer North Atlantic surface waters and stronger Atlantic overturning during the early LIG (126 ka) than the late LIG (122 ka). Hence, insolation variations alone do not explain the delay in peak interglacial conditions observed at high northern latitudes. Additionally, we consider an idealized meltwater scenario at 126 ka where the freshwater input is interactively computed in response to the high boreal summer insolation. The model simulates colder, fresher North Atlantic surface waters and weaker Atlantic overturning during the early LIG (126 ka) compared to the late LIG (122 ka). This result suggests that both insolation and ice sheet melting have to be considered to reproduce the climatic pattern that we identify during the early LIG. Our model-data comparison also reveals a number of limitations and reinforces the need for further detailed investigations using coupled climate-ice sheet models and transient simulations.
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Govin, A., P. Braconnot, E. Capron, E. Cortijo, J. C. Duplessy, E. Jansen, L. Labeyrie et al. « Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial ». Climate of the Past Discussions 7, no 5 (11 octobre 2011) : 3239–86. http://dx.doi.org/10.5194/cpd-7-3239-2011.
Texte intégralRésumé :
Abstract. Although the Last Interglacial (LIG) is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It suggests that the input of meltwater has maintained (1) colder and fresher surface-water conditions in the North Atlantic, Labrador and Norwegian Seas and (2) weaker ventilation of North Atlantic deep waters during the early LIG (129–125.5 ka) compared to the late LIG. Results from an ocean-atmosphere coupled model with insolation as a sole forcing for three key periods of the LIG show that insolation variations alone lead to warmer North Atlantic surface waters and stronger Atlantic overturning during the early LIG (126 ka) than the late LIG (122 ka). Hence insolation variations alone do not explain the delay in peak interglacial conditions observed at high northern latitudes. When freshwater input is interactively computed at 126 ka in response to the high boreal summer insolation, the model simulates colder, fresher North Atlantic surface waters and weaker Atlantic overturning during the early LIG (126 ka) compared to the late LIG (122 ka). This result indicates that both insolation variations and ice sheet melting have to be considered to reproduce the LIG climate evolution and supports our hypothesis that optimal thermal and deep ocean circulation conditions at high northern latitudes develop during the late LIG only, when the freshwater supply has already ceased.
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Pados-Dibattista, Teodora, Christof Pearce, Henrieka Detlef, Jørgen Bendtsen et Marit-Solveig Seidenkrantz. « Holocene palaeoceanography of the Northeast Greenland shelf ». Climate of the Past 18, no 1 (20 janvier 2022) : 103–27. http://dx.doi.org/10.5194/cp-18-103-2022.
Texte intégralRésumé :
Abstract. The Northeast Greenland shelf is highly sensitive to climate and ocean variability because it is swept by the East Greenland Current, which, through the western Fram Strait, forms the main pathway of export of sea ice and cold water masses from the Arctic Ocean into the North Atlantic Ocean. In order to reconstruct the variability of the East Greenland Current and general palaeoceanographic conditions in the area during the Holocene, we carried out benthic foraminiferal assemblage, stable isotope, and sedimentological analyses of a marine sediment core retrieved from the Northeast Greenland shelf (core DA17-NG-ST07-73G). The results reveal significant variations in the water masses and thus in the strength of the East Greenland Current over the last ca. 9.4 kyr. Between 9.4 and 8.2 ka the water column off Northeast Greenland was highly stratified, with cold, sea-ice-loaded surface waters and a strong influx of warm Atlantic Water in the subsurface. At ∼ 8.4 ka a short-lived peak in terrestrial elements may be linked to an influx of iceberg-transported sediments and thus to the so-called 8.2 ka event. Conditions similar to those of the Holocene Thermal Maximum prevailed from 8.2 to 6.2 ka, with a strong influence of the Return Atlantic Current and a weakened transport of Polar Water in the upper East Greenland Current. After 6.2 ka we recorded a return to a more stratified water column with sea-ice-loaded surface waters and still Atlantic-sourced subsurface waters. After 4.2 ka increased Polar Water at the surface of the East Greenland Current and a reduction in the Return Atlantic Water at subsurface levels signifies freshening and reduced stratification of the water column and (near) perennial sea-ice cover. The neoglaciation started at 3.2 ka at our location, characterized by a strengthened East Greenland Current. Cold subsurface-water conditions with possible sea-ice cover and minimum surface-water productivity persisted here throughout the last ∼ 3 kyr.
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de Vera, Alejandro, et Roger R. Seapy. « Atlanta selvagensis, a new species of heteropod mollusc from the Northeastern Atlantic Ocean (Gastropoda : Carinarioidea) ». Vieraea Folia scientiarum biologicarum canariensium 34, Vieraea 34 (2006) : 45–54. http://dx.doi.org/10.31939/vieraea.2006.34.06.
Texte intégralRésumé :
A new species of atlantid heteropod, Atlanta selvagensis, is described on the basis of external shell structure and pigmentation, and the morphologies of the eye and operculum. All specimens were collected from waters around the Selvagens Islands in the eastern North Atlantic Ocean. Species of Atlanta that share similar features with A. selvagensis are A. peroni, A. gaudichaudi and A. plana.
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James, Travis L., Sean J. Landsman, Laura L. Ramsay, Melanie D. Giffin, Arnault Le Bris et Michael R. van den Heuvel. « Migration patterns of Atlantic halibut captured in the southern Gulf of St. Lawrence as assessed with pop-up satellite archival and Floy tags ». Canadian Journal of Fisheries and Aquatic Sciences 77, no 7 (juillet 2020) : 1233–42. http://dx.doi.org/10.1139/cjfas-2019-0262.
Texte intégralRésumé :
This study provides evidence of two subpopulations of Atlantic halibut (Hippoglossus hippoglossus) in the southern Gulf of St. Lawrence. The migrations of 20 Atlantic halibut captured in the coastal waters of Prince Edward Island, Canada, were evaluated using pop-up satellite archival tags (PSAT). Geolocation data showed that Atlantic halibut migrated north to the Laurentian Channel via distinct eastern or western routes. Floy tagging and recapture (recapture of 18.4%) showed that less than 7.0% of Atlantic halibut exhibited dispersive behaviour outside of their annual migratory route. Overwintering occurred on the slope and in the deepest waters of the Laurentian Channel. Atlantic halibut in the deepest waters of the Laurentian Channel exhibited rapid, ∼100 m rises, presumed to be associated with spawning from January to March. The eastern and western migratory cohorts exhibited this behaviour ∼350 km apart, suggesting reproductive isolation as the basis of subpopulations. The results of this study indicate a need to reconsider the management of Gulf of St. Lawrence Atlantic halibut as one continuous population.
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RÍOS, PILAR, et JAVIER CRISTOBO. « Abyssocladia vaceleti (Porifera, Cladorhizidae) : a new deep-sea carnivorous sponge from Patagonia ». Zootaxa 4466, no 1 (31 août 2018) : 164. http://dx.doi.org/10.11646/zootaxa.4466.1.13.
Texte intégralRésumé :
This study describes a new species of carnivorous sponge (Family Cladorhizidae) collected in Patagonia, SW Atlantic, off Argentinean waters and the North of the Falkland Islands (Malvinas). The species described here, belongs to the genus Abyssocladia and was collected by dredging and trawling during IEO (Spanish Institute of Oceanography) cruises in the South West Atlantic Ocean from 2007 to 2010 under the Atlantis Project. Abyssocladia vaceleti sp. nov. is characterised by the possession of a long peduncle and flat body with bilaterally symmetrical and apical filaments with a skeleton of tornotes (often polytylotes), styles, abyssochelae, arcuate chelae, sigmancistras and acanthotylostrongyles. This species lives at depths of 901–1547 m.
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Straneo, Fiammetta, David A. Sutherland, David Holland, Carl Gladish, Gordon S. Hamilton, Helen L. Johnson, Eric Rignot, Yun Xu et Michele Koppes. « Characteristics of ocean waters reaching Greenland's glaciers ». Annals of Glaciology 53, no 60 (2012) : 202–10. http://dx.doi.org/10.3189/2012aog60a059.
Texte intégralRésumé :
AbstractInteraction of Greenland’s marine-terminating glaciers with the ocean has emerged as a key term in the ice-sheet mass balance and a plausible trigger for their recent acceleration. Our knowledge of the dynamics, however, is limited by scarcity of ocean measurements at the glacier/ocean boundary. Here data collected near six marine-terminating glaciers (79 North, Kangerdlugssuaq, Helheim and Petermann glaciers, Jakobshavn Isbræ, and the combined Sermeq Kujatdleq and Akangnardleq) are compared to investigate the water masses and the circulation at the ice/ocean boundary. Polar Water, of Arctic origin, and Atlantic Water, from the subtropical North Atlantic, are found near all the glaciers. Property analysis indicates melting by Atlantic Water (AW; found at the grounding line depth near all the glaciers) and the influence of subglacial discharge at depth in summer. AW temperatures near the glaciers range from 4.5˚C in the southeast, to 0.16˚C in northwest Greenland, consistent with the distance from the subtropical North Atlantic and cooling across the continental shelf. A review of its offshore variability suggests that AW temperature changes in the fjords will be largest in southern and smallest in northwest Greenland, consistent with the regional distribution of the recent glacier acceleration.