Comparison of the nematode fauna from the Weddell Sea Abyssal Plain with two North Atlantic abyssal sites

Abstract Despite the renewed interest in the Southern Ocean, there are yet many unknowns because of the scarcity of measurements and the complexity of the thermohaline circulation. Hence the authors present here the analysis of the thermohaline circulation of the Southern Ocean of a steady-state simulation of a coupled ice–ocean model. The study aims to clarify the roles of surface fluxes and internal mixing, with focus on the mechanisms of the upper branch of the overturning. A quantitative dynamical analysis of the water-mass transformation has been performed using a new method. Surface fluxes, including the effect of the penetrative solar radiation, produce almost 40 Sv (1 Sv ≡ 106 m3 s−1) of Subantarctic Mode Water while about 5 Sv of the densest water masses (γ > 28.2) are formed by brine rejection on the shelves of Antarctica and in the Weddell Sea. Mixing transforms one-half of the Subantarctic Mode Water into intermediate water and Upper Circumpolar Deep Water while bottom water is produced by Lower Circumpolar Deep Water and North Atlantic Deep Water mixing with shelf water. The upwelling of part of the North Atlantic Deep Water inflow is due to internal processes, mainly downward propagation of the surface freshwater excess via vertical mixing at the base of the mixed layer. A complementary Lagrangian analysis of the thermohaline circulation will be presented in a companion paper.

Download Full-text

Late Quaternary Ostracode From a Core in the Weddel Sea, Antartica

Pesquisas em Geociências ◽

10.22456/1807-9806.21130 ◽

1999 ◽

Vol 26 (1) ◽

pp. 11 ◽

Cited By ~ 2

Author(s):

ROBIN WHATLEY ◽

RAYMOND ROBERTS

Keyword(s):

Species Diversity ◽

North Atlantic ◽

Late Quaternary ◽

Weddell Sea ◽

The Core ◽

Constituent Species ◽

Low Diversity ◽

Relationship Of ◽

The Antarctic ◽

The Relationship

Fifty-nine samples from a 560cm gravity core of late Quaternary age (PS1003-2), collected at a depth of 2796m in the Weddell Sea, were examined for Ostracoda. The fauna was sparse but, from a total of 556 valves, the rather low diversity fauna of 19 species belonging to 11 genera and 3 families was identified. The study is principally concerned with species diversity, originations and extinctions, inter-relationships between species and the relationship of the fauna to different water masses. With respect to species diversity and origination/extinction patterns, two distinct phases are apparent: an initial diversification (originations only), followed by a phase of overall stable diversity (originations approximately matched by extinctions). The ostracod fauna is closely comparable to that described by authors as typical of North Atlantic Deep Water but is actually from the Antarctic Bottom Water (AABW). Two of the principal constituent species Henryhowella dasyderma (Brady) and H. asperrima (Ruess) seem to be mutually exclusive within the core. Changes in the fauna through the core seem to be related to climatic cycles.

Download Full-text

Early diagenetic reactions in interbedded pelagic and turbiditic sediments in the Nares Abyssal Plain (western North Atlantic): Consequences for the composition of sediment and interstitial water

Geochimica et Cosmochimica Acta ◽

10.1016/0016-7037(86)90209-7 ◽

1986 ◽

Vol 50 (12) ◽

pp. 2543-2561 ◽

Cited By ~ 72

Author(s):

G.J. De Lange

Keyword(s):

North Atlantic ◽

Interstitial Water ◽

Abyssal Plain ◽

Diagenetic Reactions

Download Full-text

The factors controlling vertical color variations of North Atlantic Madeira Abyssal Plain sediments

Marine Geology ◽

10.1016/0025-3227(92)90222-4 ◽

1992 ◽

Vol 109 (1-2) ◽

pp. 83-94 ◽

Cited By ~ 30

Author(s):

Seiya Nagao ◽

Satoru Nakashima

Keyword(s):

North Atlantic ◽

Abyssal Plain

Download Full-text

Geochemical evidence of pore-water advection along a fault in plastic sediments from the Southern Nares Abyssal Plain (western North Atlantic)

Chemical Geology ◽

10.1016/0009-2541(89)90020-x ◽

1989 ◽

Vol 75 (1-2) ◽

pp. 43-60 ◽

Cited By ~ 1

Author(s):

Dale E. Buckley

Keyword(s):

Pore Water ◽

North Atlantic ◽

Abyssal Plain ◽

Geochemical Evidence

Download Full-text

Assimilation of Radiocarbon and Chlorofluorocarbon Data to Constrain Deep and Bottom Water Transports in the World Ocean

Journal of Physical Oceanography ◽

10.1175/jpo3011.1 ◽

2007 ◽

Vol 37 (2) ◽

pp. 259-276 ◽

Cited By ~ 43

Author(s):

Reiner Schlitzer

Keyword(s):

Southern Ocean ◽

North Atlantic ◽

Bottom Water ◽

World Ocean ◽

Weddell Sea ◽

Global Ocean ◽

Western Boundary ◽

Boundary Current ◽

The North ◽

The North Atlantic

Abstract A coarse-resolution global model with time-invariant circulation is fitted to hydrographic and tracer data by means of the adjoint method. Radiocarbon and chlorofluorocarbon (CFC-11 and CFC-12) data are included to constrain deep and bottom water transport rates and spreading pathways as well as the strength of the global overturning circulation. It is shown that realistic global ocean distributions of hydrographic parameters and tracers can be obtained simultaneously. The model correctly reproduces the deep ocean radiocarbon field and the concentrations gradients between different basins. The spreading of CFC plumes in the deep and bottom waters is simulated in a realistic way, and the spatial extent as well as the temporal evolution of these plumes agrees well with observations. Radiocarbon and CFC observations place upper bounds on the northward transports of Antarctic Bottom Water (AABW) into the Pacific, Atlantic, and Indian Oceans. Long-term mean AABW transports larger than 5 Sv (Sv ≡ 106 m3 s−1) through the Vema and Hunter Channels in the South Atlantic and net AABW transports across 30°S into the Indian Ocean larger than 10 Sv are found to be incompatible with CFC data. The rates of equatorward deep and bottom water transports from the North Atlantic and Southern Ocean are of similar magnitude (15.7 Sv at 50°N and 17.9 Sv at 50°S). Deep and bottom water formation in the Southern Ocean occurs at multiple sites around the Antarctic continent and is not confined to the Weddell Sea. A CFC forecast based on the assumption of unchanged abyssal transports shows that by 2030 the entire deep west Atlantic exhibits CFC-11 concentrations larger than 0.1 pmol kg−1, while most of the deep Indian and Pacific Oceans remain CFC free. By 2020 the predicted CFC concentrations in the deep western boundary current (DWBC) in the North Atlantic exceed surface water concentrations and the vertical CFC gradients start to reverse.

Download Full-text