scholarly journals Comparison of water mass changes in the deep tropical Atlantic derived from Cd/Ca and carbon isotope records: Implications for changing Ba composition of Deep Atlantic Water Masses

1998 ◽  
Vol 13 (6) ◽  
pp. 572-585 ◽  
Author(s):  
Pamela A. Martin ◽  
David W. Lea
Keyword(s):  
Carbon Isotope ◽  
Water Mass ◽  
Atlantic Water ◽  
Water Masses ◽  
Tropical Atlantic

scholarly journals Observed trends of anthropogenic acidification in North Atlantic water masses

2012 ◽  
Vol 9 (3) ◽  
pp. 3003-3030
Author(s):  
M. Vázquez-Rodríguez ◽  
F. F. Pérez ◽  
A. Velo ◽  
A. F. Ríos ◽  
H. Mercier
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Deep Convection ◽  
Temporal Trends ◽  
Atlantic Water ◽  
Water Masses ◽  
The North ◽  
Iceland Basin ◽  
The North Atlantic ◽  
Atmospheric Co2 Concentrations

Abstract. The lack of observational pH data has made difficult assessing recent rates of ocean acidification, particularly in the high latitudes. Here we present a time series of high-quality carbon system measurements in the North Atlantic, comprising fourteen cruises spanning over 27 yr (1981–2008) and covering important water mass formation areas like the Irminger and Iceland basins. We provide direct quantification of anthropogenic acidification rates in upper and intermediate North Atlantic waters by removing the natural variability of pH from the observations. Bottle data were normalised to basin-average conditions using climatological data and further condensed into averages per water mass and year to examine the temporal trends. The highest acidification rates of all inspected water masses were associated with surface waters in the Irminger Sea (−0.0018 ± 0.0001 yr−1) and the Iceland Basin (−0.0012 ± 0.0002 yr−1) and, unexpectedly, with Labrador Seawater (LSW) which experienced an unprecedented pH drop of −0.0015 ± 0.001 yr−1. The latter stems from the formation by deep convection and the rapid propagation in the North Atlantic subpolar gyre of this well-ventilated water mass. The high concentrations of anthropogenic CO2 are effectively transported from the surface into intermediate waters faster than via downward diffusion, thus accelerating the acidification rates of LSW. An extrapolation of the observed lineal trends of acidification suggests that the pH of LSW could drop 0.45 units with respect to pre-industrial levels by the time atmospheric CO2 concentrations double the present ones.

Water Mass Transformation and Subduction in the South Atlantic

2005 ◽  
Vol 35 (10) ◽  
pp. 1841-1860 ◽  
Author(s):  
J. Donners ◽  
S. S. Drijfhout ◽  
W. Hazeleger
Keyword(s):  
Surface Water ◽  
Indian Ocean ◽  
Mixed Layer ◽  
Water Mass ◽  
South Atlantic ◽  
Water Masses ◽  
Intermediate Water ◽  
Tropical Atlantic ◽  
The South ◽  
The Indian Ocean

Abstract The transformation of water masses induced by air–sea fluxes in the South Atlantic Ocean is calculated with a global ocean model, Ocean Circulation and Climate Advanced Modeling (OCCAM), and has been compared with several observational datasets. Air–sea interaction supplies buoyancy to the ocean at almost all density levels. The uncertainty of the estimates of water mass transformations is at least 10 Sv (Sv ≡ 106 m3 s−1), largely caused by the uncertainties in heat fluxes. Further analysis of the buoyancy budget of the mixed layer in the OCCAM model shows that diffusion extracts buoyancy from the water column at all densities. In agreement with observations, water mass formation of surface water by air–sea interaction is completely balanced by consumption from diffusion. There is a large interocean exchange with the Indian and Pacific Oceans. Intermediate water is imported from the Pacific, and light surface water is imported from the Indian Ocean. South Atlantic Central Water and denser water masses are exported to the Indian Ocean. The air–sea formation rate is only a qualitative estimate of the sum of subduction and interocean exchange. Subduction generates teleconnections between the South Atlantic and remote areas where these water masses reemerge in the mixed layer. Therefore, the subduction is analyzed with a Lagrangian trajectory analysis. Surface water obducts in the South Atlantic, while all other water masses experience net subduction. The subducted Antarctic Intermediate Water and Subantarctic Mode Water reemerge mainly in the Antarctic Circumpolar Current farther downstream. Lighter waters reemerge in the eastern tropical Atlantic. As a result, the extratropical South Atlantic has a strong link with the tropical Atlantic basin and only a weak direct link with the extratropical North Atlantic. The impact of the South Atlantic on the upper branch of the thermohaline circulation is indirect: water is significantly transformed by air–sea fluxes and mixing in the South Atlantic, but most of it reemerges and subducts again farther downstream.

scholarly journals Water mass evolution of the Greenland Sea since late glacial times

2014 ◽  
Vol 10 (1) ◽  
pp. 123-136 ◽  
Author(s):  
M. M. Telesiński ◽  
R. F. Spielhagen ◽  
H. A. Bauch
Keyword(s):  
Sea Ice ◽  
Water Mass ◽  
Environmental Variability ◽  
Deep Convection ◽  
Sediment Cores ◽  
Late Glacial ◽  
Atlantic Water ◽  
Water Masses ◽  
Greenland Sea ◽  
The Holocene

Abstract. Four sediment cores from the central and northern Greenland Sea basin, a crucial area for the renewal of North Atlantic deep water, were analyzed for planktic foraminiferal fauna, planktic and benthic stable oxygen and carbon isotopes as well as ice-rafted debris to reconstruct the environmental variability in the last 23 kyr. During the Last Glacial Maximum, the Greenland Sea was dominated by cold and sea-ice bearing surface water masses. Meltwater discharges from the surrounding ice sheets affected the area during the deglaciation, influencing the water mass circulation. During the Younger Dryas interval the last major freshwater event occurred in the region. The onset of the Holocene interglacial was marked by an increase in the advection of Atlantic Water and a rise in sea surface temperatures (SST). Although the thermal maximum was not reached simultaneously across the basin, benthic isotope data indicate that the rate of overturning circulation reached a maximum in the central Greenland Sea around 7 ka. After 6–5 ka a SST cooling and increasing sea-ice cover is noted. Conditions during this so-called "Neoglacial" cooling, however, changed after 3 ka, probably due to enhanced sea-ice expansion, which limited the deep convection. As a result, a well stratified upper water column amplified the warming of the subsurface waters in the central Greenland Sea, which were fed by increased inflow of Atlantic Water from the eastern Nordic Seas. Our data reveal that the Holocene oceanographic conditions in the Greenland Sea did not develop uniformly. These variations were a response to a complex interplay between the Atlantic and Polar water masses, the rate of sea-ice formation and melting and its effect on vertical convection intensity during times of Northern Hemisphere insolation changes.

scholarly journals Variability of water mass properties in the Strait of Sicily in summer period of 1998–2013

2014 ◽  
Vol 11 (2) ◽  
pp. 811-837 ◽  
Author(s):  
A. Bonanno ◽  
F. Placenti ◽  
G. Basilone ◽  
R. Mifsud ◽  
S. Genovese ◽  
...  
Keyword(s):  
Thermohaline Circulation ◽  
Water Mass ◽  
Eastern Mediterranean ◽  
Subsurface Layer ◽  
Atlantic Water ◽  
Point Of View ◽  
Water Masses ◽  
Intermediate Water ◽  
Layer System ◽  
Strait Of Sicily

Abstract. The Strait of Sicily plays a crucial role in determining the water mass exchanges and related properties between western and eastern Mediterranean. The presence of sills to the east and west of the Strait of Sicily and the complex seabed topography modulate the thermohaline circulation of the Mediterranean basin. An anti-estuarine circulation is mainly characterized, from a dynamic point of view, by a two-layer system: a surface layer composed of Atlantic Water (AW) flowing eastward, essentially dominated by mesoscale processes, and a subsurface layer composed of Levantine Intermediate Water (LIW) flowing in the opposite direction; the topography appears to play an important role. Furthermore, there are transition water masses with variable hydrological characteristics. The dataset here studied is a time series 16 years long (1998–2013), which highlights the high horizontal and vertical interannual variability affecting the study area. Strong temperature-salinity correlations, in the intermediate layer, for specific time intervals, could be linked to the reversal of sub-surface circulation in the Central Ionian Sea. Moreover, a long-term monitoring of the hydrographic properties of water masses across this strait allow the modelers to assess the performance of hydrological models of this area.

scholarly journals Latest Miocene restriction of the Mediterranean Outflow Water: a perspective from the Gulf of Cádiz

2021 ◽  
Vol 41 (2) ◽  
Author(s):  
Zhi Lin Ng ◽  
F. Javier Hernández-Molina ◽  
Débora Duarte ◽  
Francisco J. Sierro ◽  
Santiago Ledesma ◽  
...  
Keyword(s):  
Mass Exchange ◽  
Water Mass ◽  
Atlantic Water ◽  
Meridional Overturning Circulation ◽  
Gulf Of Cadiz ◽  
Mediterranean Outflow Water ◽  
Gulf Of Cádiz ◽  
Mediterranean Outflow ◽  
The Mediterranean ◽  
Water Mass Exchange

AbstractThe Mediterranean-Atlantic water mass exchange provides the ideal setting for deciphering the role of gateway evolution in ocean circulation. However, the dynamics of Mediterranean Outflow Water (MOW) during the closure of the Late Miocene Mediterranean-Atlantic gateways are poorly understood. Here, we define the sedimentary evolution of Neogene basins from the Gulf of Cádiz to the West Iberian margin to investigate MOW circulation during the latest Miocene. Seismic interpretation highlights a middle to upper Messinian seismic unit of transparent facies, whose base predates the onset of the Messinian salinity crisis (MSC). Its facies and distribution imply a predominantly hemipelagic environment along the Atlantic margins, suggesting an absence or intermittence of MOW preceding evaporite precipitation in the Mediterranean, simultaneous to progressive gateway restriction. The removal of MOW from the Mediterranean-Atlantic water mass exchange reorganized the Atlantic water masses and is correlated to a severe weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a period of further cooling in the North Atlantic during the latest Miocene.

Paleoceanographic evolution of the SW Svalbard margin (76°N) since 20,000 14C yr BP

2007 ◽  
Vol 67 (1) ◽  
pp. 100-114 ◽  
Author(s):  
Tine L. Rasmussen ◽  
Erik Thomsen ◽  
Marta A. Ślubowska ◽  
Simon Jessen ◽  
Anders Solheim ◽  
...  
Keyword(s):  
Surface Water ◽  
Water Mass ◽  
Atlantic Water ◽  
Subsurface Water ◽  
Planktic Foraminifera ◽  
Surface Conditions ◽  
Polar Surface ◽  
Warm Core ◽  
Heinrich Event ◽  
Benthic Environment

AbstractTwo cores from the southwestern shelf and slope of Storfjorden, Svalbard, taken at 389 m and 1485 m water depth have been analyzed for benthic and planktic foraminifera, oxygen isotopes, and ice-rafted debris. The results show that over the last 20,000 yr, Atlantic water has been continuously present on the southwestern Svalbard shelf. However, from 15,000 to 10,000 14C yr BP, comprising the Heinrich event H1 interval, the Bølling–Allerød interstades and the Younger Dryas stade, it flowed as a subsurface water mass below a layer of polar surface water. In the benthic environment, the shift to interglacial conditions occurred at 10,000 14C yr BP. Due to the presence of a thin upper layer of polar water, surface conditions remained cold until ca. 9000 14C yr BP, when the warm Atlantic water finally appeared at the surface. Neither extensive sea ice cover nor large inputs of meltwater stopped the inflow of Atlantic water. Its warm core was merely submerged below the cold polar surface water.

scholarly journals Characterization of the Atlantic Water and Levantine Intermediate Water in the Mediterranean Sea using Argo Float Data

2021 ◽  
Author(s):  
Giusy Fedele ◽  
Elena Mauri ◽  
Giulio Notarstefano ◽  
Pierre Marie Poulain
Keyword(s):  
Mediterranean Sea ◽  
Thermohaline Circulation ◽  
Internal Variability ◽  
Warming Trend ◽  
Atlantic Water ◽  
Western Mediterranean ◽  
Water Masses ◽  
Intermediate Water ◽  
Starting Point ◽  
The Mediterranean

Abstract. The Atlantic Water (AW) and Levantine Intermediate Water (LIW) are important water masses that play a crucial role in the internal variability of the Mediterranean thermohaline circulation. In particular, their variability and interaction, along with other water masses that characterize the Mediterranean basin, such as the Western Mediterranean Deep Water (WMDW), contribute to modify the Mediterranean Outflow through the Gibraltar Strait and hence may influence the stability of the global thermohaline circulation. This work aims to characterize the AW and LIW in the Mediterranean Sea, taking advantage of the large observational dataset provided by Argo floats from 2001 to 2019. Using different diagnostics, the AW and LIW were identified, highlighting the inter-basin variability and the strong zonal gradient that characterize the two water masses in this marginal sea. Their temporal variability was also investigated focusing on trends and spectral features which constitute an important starting point to understand the mechanisms that are behind their variability. A clear salinification and warming trend have characterized the AW and LIW in the last two decades (~0.007 and 0.008 yr−1; 0.018 and 0.007 °C yr−1, respectively). The salinity and temperature trends found at subbasin scale are in good agreement with previous results. The strongest trends are found in the Adriatic basin in both the AW and LIW properties. A subbasin dependent spectral variability emerges in the AW and LIW salinity timeseries with peaks between 2 and 10 years.

scholarly journals WATER MASSES CHARACTERISTICS AT THE SANGHIE TALAUD ENTRY PASSAGE OF INDONESIAN THROUGHFLOW USING INDEX SATAL DATA 2010

2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Ivonne M Radjawane ◽  
Paundra P Hadipoetranto
Keyword(s):  
North Pacific ◽  
Water Mass ◽  
Sea Water ◽  
Core Layer ◽  
South Pacific ◽  
New Guinea ◽  
Water Masses ◽  
Coastal Current ◽  
Indonesian Throughflow ◽  
Pacific Water

<p><strong><em>ABSTRACT</em></strong></p> <p><em>Measurement of ocean physical param</em><em>eter</em><em>s using the CTD was conducted by </em><em>deep water expedition </em><em>INDEX-SATAL 2010 (Indonesian Expedition Sangihe-Talaud) in July-August 2010. Th</em><em>e</em><em> </em><em>aim of this </em><em>study wa</em><em>s to</em><em> determine the characteristics of water masses around the Sangihe Talaud Water where the</em><em>re </em><em>wa</em><em>s an entry passage of </em><em> Indonesian throughflow (ITF) </em><em>at</em><em> </em><em>the </em><em>west </em><em>path</em><em>way that passed through the </em><em>primary</em><em> pathway i.e., </em><em>the Sulawesi</em><em> Sea and Makassar Strait and the secondary pathway (east pathway) that passed through the Halmahera Sea. The analyses were performed by the method of the core layer and was  processed with software Ocean Data View (ODV). The results showed that in the Sangihe Talaud waters there was a meeting water masses from the North Pacific and the South Pacific. The water mass characteristics in main pathway through the Sulawesi Sea was dominated by surface and intermediate North Pacific water masses and carried by the Mindanao Currents. While the Halmahera Sea water mass was dominated by surface and intermediate South Pacific water masses carried by the New Guinea Coastal Current that moved along the Papua New Guinea and Papua coast enters to the Halmahera Sea. </em></p> <p><em> </em></p> <p><strong><em>Keywords</em></strong><em>: Index-Satal 2010, Northern Pacific Water Mass</em><em>es</em><em>, Southern Pacific Water </em></p> <em> Masses, Sangihe Talaud</em>

Eemian Climatic and Hydrographical Instability on a Marine Shelf in Northern Denmark

1997 ◽  
Vol 47 (2) ◽  
pp. 218-234 ◽  
Author(s):  
Marit-Solveig Seidenkrantz ◽  
Karen Luise Knudsen
Keyword(s):  
Ocean Circulation ◽  
Atlantic Water ◽  
Water Masses ◽  
Last Interglacial ◽  
Large Shift ◽  
The North ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
First Millennium ◽  
Holocene Record

Benthic foraminifera and stable isotope data from the last interglaciation (Eemian, substage 5e) from a borehole at Skagen, Denmark, provide evidence for major environmental and hydrographic changes during this period. During the first millennium of the Eemian, water masses covering northern Denmark became gradually warmer. Temperate conditions prevailed during most of the interglaciation, but these were interrupted by two periods with decreased water temperatures. The first cooling (Event S-1) was not very distinct at Skagen, but the second (Event S-2), seen in both the foraminiferal and oxygen isotope record, represents a large shift to subarctic conditions. Carbon isotopes indicate a change in ocean circulation during both events. No comparable climate variations are seen within the Holocene record at the site. The final cooling of the water masses associated with the substage 5e/5d boundary occurred within a few hundred years. These last interglacial climatic changes were probably caused by variations in strength and/or position of the North Atlantic Drift, possibly as a result of varying vigor of the Atlantic conveyor. In addition, minor variations in the fossil assemblages also indicate fluctuations in the inflow of Atlantic water to the Skagerrak–Kattegat area during the warm intervals of substage 5e.

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