Recirculating components to the deep boundary current of the northern North Atlantic

McCartney, Michael S.

doi:10.1016/0079-6611(92)90006-l

Cited by 284 publications

(190 citation statements)

References 37 publications

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“…This would indicate that water masses with similar or more positive ε Nd signatures were admixed to the bottom waters of deep site 900, which most likely overflowed from the GIN seas as part of the Iceland-Scotland overflow water (ISOW; modern ε Nd = −8; Lacan and Jeandel, 2005) and were then advected across the Iceland-Scotland gap into the recirculation gyre south of the Iceland Basin (McCartney, 1992; Figs. 1 and 2).…”

Section: Resultsmentioning

confidence: 99%

“…2). This lower NADW fills most of the northeast Atlantic below 2500 m today (McCartney, 1992 (Jeandel, 1993;Stichel et al, 2012), site 900 should be sensitive to changes in the relative influence of northern versus southern source waters, as has been demonstrated for other sites further south on glacial-interglacial timescales of the latest Quaternary (e.g., Roberts et al, 2010).…”

Section: Study Areamentioning

confidence: 99%

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A major change in North Atlantic deep water circulation 1.6 million years ago

Khélifi

2014

Clim. Past

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Abstract. The global ocean-climate system has been highly sensitive to the formation and advection of deep overflow water from the Nordic Seas as integral part of the Atlantic Meridional Overturning Circulation (AMOC) but its evolution over the Pliocene-Pleistocene global cooling is not fully understood. In particular, changes in the sources and mixing of prevailing deep waters that were involved in driving overturning throughout the Pliocene-Pleistocene climate transitions are not well constrained. Here we investigate the evolution of a substantial deep southward return overflow of the AMOC over the last 4 million years. We present new records of the bottom-water radiogenic neodymium isotope (ε Nd ) variability obtained from three sediment cores (DSDP site 610 and ODP sites 980/981 and 900) at water depths between 2170 and 5050 m in the northeast Atlantic. We find that prior to the onset of major Northern Hemisphere glaciation (NHG) ∼ 3 million years ago (Ma), ε Nd values primarily oscillated between −9 and −11 at all sites, consistent with enhanced vertical mixing and weak stratification of the water masses during the warmer-than-today Pliocene period. From 2.7 Ma to ∼ 2.0 Ma, the ε Nd signatures of the water masses gradually became more distinct, which documents a significant advection of Nordic Seas overflow deep water coincident with the intensification of NHG. Most markedly, however, at ∼ 1.6 Ma the interglacial ε Nd signatures at sites 610 (2420 m water depth (w.d.)) and 980/981 (2170 m w.d.) synchronously and permanently shifted by 2 to 3 ε Nd units to less radiogenic values, respectively. Since then the difference between glacial and interglacial ε Nd values has been similar to the Late Quaternary at each site. A decrease of ∼ 2 ε Nd units at 1.6 Ma was also recorded for the deepest water masses by site 900 (∼ 5 050 m w.d.), which thereafter, however, evolved to more radiogenic values again until the present. This major ε Nd change across the 1.6 Ma transition reflects a significant reorganization of the overturning circulation in the northeast Atlantic paving the way for the more stratified water column with distinct water masses prevailing thereafter.

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Section: Resultsmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

A major change in North Atlantic deep water circulation 1.6 million years ago

Khélifi

2014

Clim. Past

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“…Bain and Russell, 1980;Weaver, 1989). In the NEADW2, the main component from the Norwegian Sea outflow is mixed with warmer and more saline waters from the deep temperate Atlantic, with a small influx of Antarctic Bottom Water (McCartney, 1992;Dickson and Brown, 1994;Lucotte and HillaireMarcel, 1994). This composite NEADW2 contains a slightly different clay association, characterized by higher proportions of beidellite within the smectites probably of a distant origin.…”

Section: Clay Mineralogical Imprint Of Modern Deep Water Massesmentioning

confidence: 99%

“…Al-Fe smectites contribute for 30-40% of the clay assemblages of surface sediments in the adjacent Bay of Biscaye (e.g. Debrabant et al, 1979) (McCartney, 1992;Dickson and Brown, 1994).…”

Section: Sources Of Terrigenous Smectitesmentioning

confidence: 99%

Smectite composition as a tracer of deep circulation: the case of the Northern North Atlantic

et al. 2001

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The link between smectite composition in sediments from the northern North Atlantic and Labrador Sea, and deep circulation is being further investigated through detailed studies of the X-ray pattern of smectites and cation saturations. This allows clear distinction of dominant terrigenous sources associated to the main components of the modern Western Boundary Undercurrent. Time variations of smectite characteristics in two piston cores from the inlet and outlet of the Western Boundary Undercurrent gyre in the Labrador Sea indicate: (1)

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“…We introduced additional constraints in an extended inverse model for a third calculation of the geostrophic flow with more detail on basin scales (e.g., barotropic recirculation within basins). The Lower Deep Water (LDW), characterized by high dissolved silica values due to its large Antarctic Bottom Water content, as well as the low-salinity Labrador Sea Water (LSW) are assumed not to participate in the exchange between the Atlantic Ocean and the Nordic Seas (McCartney, 1992;Van Aken, 1995;Stoll et al, 1996-this issue). Therefore we added as extra constraints no net flow of water within the high dissolved silica core (Si > 12 pmol kg-') originating from the LDW in the Irminger Sea, the Iceland Basin and the Rockall Channel separately; and no net meridional flow in the lowsalinity cores of the LSW in the three basins separately (S < 35.00 in the Rockall Channel, S < 34.95 in the Iceland Basin, and S < 34.90 in the Irminger Sea).…”

Section: Determination Of the Flow Fieldmentioning

confidence: 99%

Meridional carbon dioxide transport in the northern North Atlantic

et al. 1996

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Combination of estimated water transport and accurate measurements of total carbon dioxide (TCO,) on a hydrographic section at 58"N allows the assessment of meridional inorganic carbon transport in the northern North Atlantic Ocean. The transport has been decomposed into contributions from the large-scale baroclinic overturning, the Ekman transport, baroclinic and a barotropic eddy terms, and an estimated contribution of the East Greenland Current. North Atlantic, using our flux estimates as well as those of Brewer et al. (1989). This budget shows that the divergence of the meridional carbon flux, connected with the freshwater balance of the ocean may be of the same order of magnitude as the divergence of the total inorganic carbon flux. For an accurate estimate of the total carbon budget of the ocean it will be necessary to take both the DOC transport and the effects of the freshwater balance into account.

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Recirculating components to the deep boundary current of the northern North Atlantic

Cited by 284 publications

References 37 publications

A major change in North Atlantic deep water circulation 1.6 million years ago

A major change in North Atlantic deep water circulation 1.6 million years ago

Smectite composition as a tracer of deep circulation: the case of the Northern North Atlantic

Meridional carbon dioxide transport in the northern North Atlantic

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