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Registros recuperados: 24
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A 130,000-year record of Levantine Intermediate Water flow variability in the Corsica Trough, western Mediterranean Sea ArchiMer
Toucanne, Samuel; Jouet, Gwenael; Ducassou, Emmanuelle; Bassetti, Maria-angela; Dennielou, Bernard; Minto'O, Charlie Morelle Angue; Lahmi, Marjolaine; Touyet, Nicolas; Charlier, Karine; Lericolais, Gilles; Mulder, Thierry.
Sortable silt particle-size data and stable isotope analyses from the Corsica Trough, western Mediterranean Sea, provide a continuous palaeoceanographic record of the inflow, ventilation and vertical fluctuations of the Levantine Intermediate Water (LIW) in the northern Tyrrhenian Sea for the last 130,000 years. The results presented herein reveal that climate changes drive the Mediterranean intermediate circulation on Milankovitch to millennial time-scales. Intensified intermediate inflow and ventilation in the Corsica Trough occurred throughout the last glacial interval, with a cold / faster – warm / slower pattern existing between the Dansgaard-Oeschger climatic oscillations (including Heinrich events) and the LIW variability. By contrast, a weak...
Tipo: Text Palavras-chave: Levantine Intermediate Water; Mediterranean Sea; Thermohaline circulation; Palaeoceanography.
Ano: 2012 URL: https://archimer.ifremer.fr/doc/00054/16506/14023.pdf
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A modelling study of the thermohaline circulation of the Mediterranean Sea: Water formation and dispersal ArchiMer
Haines, K; Wu, Pl.
A model of the whole Mediterranean sea at 0.25 degrees x 0.25 degrees resolution has been run for ten years with a mean seasonal cycle of forcing using NMC winds and a relaxation to NODC surface temperature and salinity. The winter season water formation and dispersal in the model thermocline has been studied using isopycnal diagnostics and potential vorticity as a water mass tracer. In the eastern basin Levantine Intermediate Water (LIW) is formed in the cyclonic Rhodes gyre and moves west in a continuous mass, accumulating and mixing in the centre of the Northern Ionian. The LIW spreading path is identified both from the high salinity and low potential vorticity values on the 28.8 isopycnal surface. Some LIW then spreads west and south towards Sicily,...
Tipo: Text Palavras-chave: PRIMO-O; Circulation thermohaline; Eau levantine intermédiaire; Formation; Modélisation; PRIMO-O; Thermohaline circulation; Levantine Intermediate Water; Water formation; Modelling.
Ano: 1995 URL: http://archimer.ifremer.fr/doc/00323/43387/43113.pdf
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Atlantic meridional overturning circulation and the Southern Hemisphere supergyre ArchiMer
Speich, Sabrina; Blanke, Bruno; Cai, Wenju.
The ocean's role in climate manifests itself through its high heat capacity, its own rich internal dynamics and its ability to transport vast quantities of heat and freshwater. Of particular interest is the global ocean circulation associated with the Atlantic meridional overturning (AMOC). Because observations are sparse, the detailed global structure of the AMOC remains poorly understood, particularly the pathways along which water returns to the Atlantic to compensate the export of North Atlantic Deep Water (NADW). Here we provide the first quantitative 3-dimensional global view of the AMOC using a Lagrangian reconstruction which integrates hundred of thousands water particle trajectories in an ocean model. The resulting pattern elucidates the role of...
Tipo: Text Palavras-chave: Antarctic circumpolar current; Indian ocean; Intermediate water; Thermohaline circulation; Pacific oceans; Conveyor belt; Model; Transport; Tracers.
Ano: 2007 URL: https://archimer.ifremer.fr/doc/00203/31420/29821.pdf
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Atlantic Meridional Overturning Circulation: Observed Transport and Variability ArchiMer
Frajka-williams, Eleanor; Ansorge, Isabelle J.; Baehr, Johanna; Bryden, Harry L.; Chidichimo, Maria Paz; Cunningham, Stuart A.; Danabasoglu, Gokhan; Dong, Shenfu; Donohue, Kathleen A.; Elipot, Shane; Heimbach, Patrick; Holliday, N. Penny; Hummels, Rebecca; Jackson, Laura C.; Karstensen, Johannes; Lankhorst, Matthias; Le Bras, Isabela A.; Lozier, M. Susan; Mcdonagh, Elaine L.; Meinen, Christopher S.; Mercier, Herle; Moat, Bengamin I.; Perez, Renellys C; Piecuch, Christopher G.; Rhein, Monika; Srokosz, Meric A.; Trenberth, Kevin E.; Bacon, Sheldon; Forget, Gael; Goni, Gustavo; Kieke, Dagmar; Koelling, Jannes; Lamont, Tarron; Mccarthy, Gerard D.; Mertens, Christian; Send, Uwe; Smeed, David A.; Speich, Sabrina; Van Den Berg, Marcel; Volkov, Denis; Wilson, Chris.
The Atlantic Meridional Overturning Circulation (AMOC) extends from the Southern Ocean to the northern North Atlantic, transporting heat northwards throughout the South and North Atlantic, and sinking carbon and nutrients into the deep ocean. Climate models indicate that changes to the AMOC both herald and drive climate shifts. Intensive trans-basin AMOC observational systems have been put in place to continuously monitor meridional volume transport variability, and in some cases, heat, freshwater and carbon transport. These observational programs have been used to diagnose the magnitude and origins of transport variability, and to investigate impacts of variability on essential climate variables such as sea surface temperature, ocean heat content and...
Tipo: Text Palavras-chave: Meridional overturning circulation; Thermohaline circulation; Observing systems; Ocean heat transport; Carbon storage; Moorings; Circulation variability.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00503/61507/65342.pdf
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Circulación y estructura termohalina en una región del Pacífico Oriental (03°16'S-31°23'S) durante un período de El Niño 1997-1998 OceanDocs
Zambrano, E.; Garcés Vargas, J..
El objetivo del presente trabajo es estudiar la estructura termohalina superficial y subsuperficial de una región del Pacífico Sudeste (Guayaquil-Valparaíso), Fig. 1, durante el término de la primavera austral de 1997 para determinar los posibles cambios en la circulación. Para esta fecha se dio comienzo la VII Expedición Ecuatoriana a la Antártida a bordo del B/I ORION y simultáneamente se estaba desarrollando un evento ENOS de intensidad fuerte.
Tipo: Journal Contribution Palavras-chave: El Nino phenomena; Thermohaline circulation; Surface temperature; T/S diagrams; Current direction; Countercurrents; Current measurement; Ocean circulation.
Ano: 1998 URL: http://hdl.handle.net/1834/2316
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Contribución al conocimiento de la oceanografía física del Estrecho Bransfield OceanDocs
Zambrano Q., E.; Cardin, V..
Durante el verano austral de 1988, el Ecuador realizó la Primera Expedición Científica a la Antártica abordo del buque oceanográfico ORION. Se investigó en detalle el Estrecho Bransfiel realizándose un total de 23 estaciones oceanográficas, en las que se tomó información desde la superficie hasta los 500 m. de profundidad, obteniéndose datos de temperatura y salinidad, además de parámetros químicos y bilógicos. En este trabajo se presenta una descripción de las condiciones oceanográficas predominantes durante las fechas del muestreo así como la estructura termohalina del estrecho; mediante el uso de diagramas T-S se identificaron las masas de agua presentes en la región. Del análisis de la topografía dinámica se deduce que la circulación es hacia NE y, en...
Tipo: Journal Contribution Palavras-chave: Temperature; Salinity; Water masses; Thermohaline circulation; Dynamic topography; Oceanographic stations; Physical oceanography; Physical oceanography; Temperature; Salinity.
Ano: 1989 URL: http://hdl.handle.net/1834/3826
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Estudios de algunas características físicas y biológicas de la columna de agua en Bahía Chile-Isla Greenwich OceanDocs
Cornejo, María P.; Arcos, F..
Se determinaron algunas características físicas y biológicas de la columna de agua en Bahía Chile, Isla Greenwich, por medio de la distribución espacial de temperatura, salinidad y clorofila "a", durante el verano austral (febrero de 1990). Las distribuciones verticales de las isotermas, isohalinas, isopicnas e isolíneas de clorfila "a" muestran que la circulación predominante es termohalina, influenciada por la topografía de la bahía, con un flujo subsuperficial que entra por el lado noroccidental de la misma y se dirige hacia el centro (siguiendo la topografía), aflora en el extremo interior y sale superficialmente por el lado oriental.
Tipo: Journal Contribution Palavras-chave: Chemical oceanography; Marine ecology; Salinity; Isotherms; Isopycnics; Thermohaline circulation; Chlorophylls; Chemical oceanography; Marine ecology; Salinity; Chlorophylls; Http://aims.fao.org/aos/agrovoc/c_1516; Http://aims.fao.org/aos/agrovoc/c_4609; Http://aims.fao.org/aos/agrovoc/c_6751; Http://aims.fao.org/aos/agrovoc/c_1577.
Ano: 1990 URL: http://hdl.handle.net/1834/3728
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Geostrophic Closure of the Zonally Averaged Atlantic Meridional Overturning Circulation ArchiMer
Sevellec, Florian; Huck, Thierry.
It is typically assumed that the meridional density gradient in the North Atlantic is well and positively correlated with the Atlantic meridional overturning circulation (AMOC). In numerical "water-hosing" experiments, for example, imposing an anomalous freshwater flux in the Northern Hemisphere leads to a slowdown of the AMOC. However, on planetary scale, the first-order dynamics are linked to the geostrophic balance, relating the north-south pressure gradient to the zonal circulation. In this study, these two approaches are reconciled. At steady state and under geostrophic dynamics, an analytical expression is derived to relate the zonal and meridional pressure gradient. This solution is only valid where the meridional density gradient length scale is...
Tipo: Text Palavras-chave: Meridional overturning circulation; Thermohaline circulation; Atm/Ocean Structure/ Phenomena; Ocean circulation; Baroclinic flows; Geographic location/entity; Ekman pumping; Circulation/ Dynamics; Atlantic Ocean.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00323/43456/42843.pdf
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Holocene climate variability in the western Mediterranean region from a deepwater sediment record ArchiMer
Frigola, J.; Moreno, A.; Cacho, I.; Canals, M.; Sierro, F. J.; Flores, J. A.; Grimalt, J. O.; Hodell, D. A.; Curtis, J. H..
The detailed analysis of the International Marine Past Global Changes Study core MD99-2343 recovered from a sediment drift at 2391 m water depth north of the island of Minorca illustrates the effects of climate variability on thermohaline circulation in the western Mediterranean during the last 12 kyr. Geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the Western Mediterranean Basin during the Holocene. Superimposed on the general trend, eight centennial- to millennial-scale abrupt events appear consistently in both grain size and geochemical records, which supports the occurrence of episodes of deepwater overturning reinforcement in the...
Tipo: Text Palavras-chave: Holocene climate variability; Thermohaline circulation; Western Mediterranean Sea.
Ano: 2007 URL: https://archimer.ifremer.fr/doc/00233/34448/32900.pdf
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Holocene long- and short-term climate changes off Adelie Land, East Antarctica ArchiMer
Crosta, X.; Debret, M.; Denis, D.; Courty, M. A.; Ther, O..
Diatom data from a marine sediment core give insight on Holocene changes in sea- surface conditions and climate at high southern latitudes off Adelie Land, East Antarctica. The early to mid- Holocene was warmer than the late Holocene with a transition at similar to 4000 calendar years B. P. Sea ice was less present and spring- summer growing season was greater during the warm period relative to the cold one, thus limiting sea ice diatom production and favoring more open ocean diatom to develop. The long- term Holocene climatic evolution in East Antarctica is explained by a combination of a delayed response to local seasonal insolation changes coupled to the long memory of the Southern Ocean. Abrupt variations of the diatom relative abundances, indicating...
Tipo: Text Palavras-chave: Antarctica; Sea ice; Holocene; Insolation; Thermohaline circulation.
Ano: 2007 URL: https://archimer.ifremer.fr/doc/00235/34642/33044.pdf
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Impact of iceberg melting on Mediterranean thermohaline circulation during Heinrich events ArchiMer
Sierro, Fj; Hodell, Da; Curtis, Jh; Flores, Ja; Reguera, I; Colmenero-hidalgo, E; Barcena, Ma; Grimalt, Jo; Cacho, I; Frigola, J; Canals, M.
Down-core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in International Marine Past Global Changes Study (IMAGES) core MD99-2343 in order to study the interactions between climate change in the Northern Hemisphere and the western Mediterranean thermohaline circulation at times of Heinrich events (HE). Our results confirm the antiphase correlation between enhanced North Atlantic Deep Water formation and low ventilation in the Mediterranean. However, this study reveals that this antiphase relationship in deepwater formation between the North Atlantic and Mediterranean was interrupted during times of HE when the injection of large volumes of water from melting icebergs reached the entrance to the Mediterranean....
Tipo: Text Palavras-chave: Climatic change; Heinrich events; Mediterranean Sea; Carbon and oxygen isotopes; Thermohaline circulation; Pleistocene.
Ano: 2005 URL: https://archimer.ifremer.fr/doc/00232/34354/32759.pdf
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Internal and forced variability along a section between Greenland and Portugal in the CLIPPER Atlantic model ArchiMer
Treguier, Anne-marie; Gourcuff, Claire; Lherminier, Pascale; Mercier, Herle; Barnier, Bernard; Madec, Gurvan; Molines, Jean-marc; Penduff, Thierry; Czeschel, Lars; Boning, Claus.
Numerical models are used to estimate the meridional overturning and transports along the paths of two hydrographic cruises, carried out in 1997 and 2002 from Greenland to Portugal. We have examined the influence of the different paths of the two cruises and found that it could explain 0.4 to 2 Sv of difference in overturning (the precise value is model-dependent). Models show a decrease in the overturning circulation between 1997 and 2002, with different amplitudes. The CLIPPER ATL6 model reproduces well the observed weakening of the overturning in density coordinates between the cruises; in the model, the change is due to the combination of interannual and high-frequency forcing and internal variability associated with eddies and meanders. Examination of...
Tipo: Text Palavras-chave: Ocean model; Thermohaline circulation; North Atlantic; Climate variability; Oceanography.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2199.pdf
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Late Holocene oceanographic and climate change from the western European margin: the results of the HOLSMEER project ArchiMer
Scourse, James; Sejrup, Hans Petter; Jones, Phil D..
The underlying aim of the HOLSMEER project has been to improve our understanding of natural climate variability through the search for, interpretation and quantification of, climatic variability in very high-resolution shallow marine records from Atlantic Europe covering the last 2000 years. This has been achieved through detailed analyses of a series of coastal and shallow marine sites spanning the Atlantic seaboard from Iberia to western Norway, and extending across to Iceland. HOLSMEER partners have documented pronounced instability in the thermohaline circulation (THC) during the period immediately prior to the recent significant anthropogenic impact on the environment. For the first time we have been able to document that these changes in the coastal...
Tipo: Text Palavras-chave: Holocene; Palaeoclimate; Marine; Thermohaline circulation; Sea level; Arctica islandica; Transfer function; HOLSMEER project; North Atlantic Ocean; Western European margin.
Ano: 2006 URL: https://archimer.ifremer.fr/doc/00234/34504/33458.pdf
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Millennial-scale variability of deep-water temperature and delta O-18(dw) indicating deep-water source variations in the Northeast Atlantic, 0-34 cal. ka BP ArchiMer
Skinner, Lc; Shackleton, Nj; Elderfield, H.
Paired measurements of Mg/Ca and delta(18)O(cc) (calcite delta(18)O) in benthic foraminifera from a deep-sea core recovered on the Iberian Margin (MD99-2334K; 37degrees 48'N, 10degrees10'W; 3,146 m) have been performed in parallel with planktonic delta(18)O(cc) analyses and counts of ice-rafted debris (IRD). The synchrony of temperature changes recorded in the Greenland ice cores and in North Atlantic planktonic delta(18)O(cc) allows the proxy records from MD99-2334K to be placed confidently on the GISP2 time-scale. This correlation is further corroborated by AMS C-14-dates. Benthic Mg/Ca measurements in MD99-2334K permit the reconstruction of past deep-water temperature (T-dw) changes since -34 cal. ka BP (calendar kiloyears before present). Using these...
Tipo: Text Palavras-chave: Deep-water temperature; Mg/Ca; Termination I; Thermohaline circulation; Paleoceanographycal and chemical : trace elements; Oceanography : biological and chemical : trace elements; Oceanography : biological and chemical : stable isotopes.
Ano: 2003 URL: https://archimer.ifremer.fr/doc/00225/33654/32087.pdf
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Propagation 3D d'ondes inertielles au sein d'un champ turbulent mésoéchelle ArchiMer
Danioux, Eric.
A current problem in physical oceanography is to identify the sources of energy at the origin of the abyssal mixing associated with thermohaline circulation. An important source is the inertial waves generated by wind. However, the mechanisms driving this energy from the surface to the deep mixing remain poorly understood. We study here the tridimensional propagation of inertial waves in a fully turbulent mesoscale eddy field with a primitive equations numerical model. After presenting a review of works to date, we describe various methods for extracting the inertial signal. The 3D propagation of inertial waves is then described and rationalized. In particular, two dramatic maxima of the vertical velocity have been found around 100 m and 1700 m. The deep...
Tipo: Text Palavras-chave: Potential vorticity; Diapycnal mixing; Thermohaline circulation; Resonance; Inertial waves; Vorticité potentielle; Mélange diapycnal; Circulation thermohaline; Résonance; Ondes inertielles.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/these-4933.pdf
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Rapid transient changes in northeast Atlantic deep water ventilation age across Termination I ArchiMer
Skinner, Lc; Shackleton, Nj.
A sequence of accelerator mass spectrometry (AMS) C-14 dates performed on benthic and planktonic foraminifera from a northeast Atlantic deep-sea core (MD99-2334K; 37degrees480N, 10degrees10'W; 3146 m) permit the reconstruction of deep water ,,C-14 ventilation ages'' across the last deglaciation. The records from MD99-2334K have been placed on the GISP2 timescale via the synchrony of temperature changes recorded in the Greenland ice cores and in North Atlantic planktonic delta(18)O(cc) (calcite delta(18)O). On the basis of a range of estimates for past source water Delta(14)C, this permits the estimation of C-14 projection ventilation ages for comparison with benthic-planktonic C-14 age differences. Although the accurate estimation of past ventilation ages...
Tipo: Text Palavras-chave: Termination I; Ventilation age; Thermohaline circulation.
Ano: 2004 URL: https://archimer.ifremer.fr/doc/00228/33971/32339.pdf
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Role of bathymetry in Agulhas Current configuration and behaviour - art. no. L23611 ArchiMer
Speich, Sabrina; Lutjeharms, J. R. E.; Penven, P; Blanke, Bruno.
The Agulhas Current forms an important link in the global ocean thermohaline circulation by its role in the interocean exchange of water south of Africa. This process of ring shedding at the current's retroflection is dependent on perturbations to its trajectory that are sensitive to bathymetry. These perturbations may furthermore force the current to intersect shallow regions resulting in substantial changes to its path. A number of other flow characteristics of the system have also been deemed to be influenced by bathymetry. How dependent is Agulhas Current behaviour therefore on the bottom topography? We have used a regional, primitive equation model for initial experimentation. Removing the Agulhas Bank leads to enhanced interocean flux, indicating its...
Tipo: Text Palavras-chave: Inter ocean exchange; Inter ocean flux; Thermohaline circulation; Southwest Africa; Agulhas current.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2308.pdf
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Salinity changes along the upper limb of the Atlantic thermohaline circulation - art. no. L06609 ArchiMer
Blanke, Bruno; Arhan, Michel; Speich, Sabrina.
Lagrangian analyses of a global ocean circulation model quantify the salinity changes experienced by the warm limb of the thermohaline circulation during the northward flow to the Atlantic deep convection regions. 6 Sv out of the estimated 10-Sv transfer from 45 degrees S to 47 degrees N flow through regions of prevailing surface evaporation: the southern and northern formation regions of Salinity Maximum Water and the Gulf of Cadiz/Mediterranean Sea domain. The remaining transport gains salinity through mixing with adjacent waters. As much as 6 Sv flow through the low-salinity surface mixed layer at the latitudes of the ITCZ whose effect annihilates that of the southern region of Salinity Maximum Water. Most of the salinity increase corresponds to the...
Tipo: Text Palavras-chave: Salinity; Atlantic deep convection zones; Upper limb; Thermohaline circulation; Ocean circulation model.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1213.pdf
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The Western Mediterranean Deep Water: A proxy for climate change - art. no. L12608 ArchiMer
Rixen, Michel; Beckers, J; Levitus, S; Antonov, J; Boyer, T; Maillard, Catherine; Fichaut, Michele; Balopoulos, E; Iona, S; Dooley, H; Garcia, M; Manca, B; Giorgetti, A; Manzella, G; Mikhailov, N; Pinardi, N; Zavatarelli, M.
Reconstructions of Mediterranean ocean temperature fields back to 1950 show a proxy relationship between heat content changes in the North Atlantic and the Western Mediterranean Deep Water ( WMDW) formed in the Gulf of Lions in winter, because of consistent air-sea heat fluxes over these areas, strongly correlated to the North Atlantic Oscillation ( NAO).
Tipo: Text Palavras-chave: North Atlantic; West mediterranee; Thermohaline circulation; Temperature variation; Deep water; Water masses; Air sea heat flux.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-760.pdf
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Variabilidad oceanográfica en Ecuador asociada con el evento ENSO 1997-98 OceanDocs
Martínez, R.; Zambrano, E.; Garcés Vargas, J..
El objetivo de este artículo es documentar científicamente la evolución del evento "El Niño" en Ecuador, desde el punto de vista oceanográfico, sugiriendo posibles mecanismos involucrados en este proceso, vinculados a ondas interestacionales Kelvin en el océano (Kessler et al., 1995) que actúan como contraparte a las oscilaciones de 60 a 75 días en la atmósfera (Maden - Julian, 1995) y más específicamente de ondas encontradas en los espectros de nivel medio del mar y TSM en el mar ecuatoriano- colombiano con estas mismas características (Martínez, 1998).
Tipo: Journal Contribution Palavras-chave: Variability; Isotherms; Thermohaline circulation; El Nino phenomena; Surface temperature; Cruises; Kelvin waves; Air temperature; Mean sea level; Salinity charts; Air temperature.
Ano: 2000 URL: http://hdl.handle.net/1834/2245
Registros recuperados: 24
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