Closure of the Global Overturning Circulation Through the Indian, Pacific, and Southern Oceans: Schematics and Transports

Talley, Lynne D.

doi:10.5670/oceanog.2013.07

Cited by 678 publications

(904 citation statements)

References 53 publications

(57 reference statements)

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“…(SV) and −5.2 SV are roughly consistent with the observed rate of NADW formation and the transport of AABW into the North Atlantic (1,2).…”

Section: Significancesupporting

confidence: 68%

“…2C), which reproduce the basic features observed in the present-day Atlantic. In particular, we see a tongue of salty water at middepth, penetrating southward into the Southern Ocean and leading to a reversal of the salinity stratification in the abyss (2). The associated overturning streamfunction (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Antarctic bottom water (AABW) is formed around Antarctica and spreads northward into the abyssal basins. The AABW that makes it into the Atlantic then slowly upwells into the lower NADW before returning southward and resurfacing again around Antarctica (1,2). The glacial equivalent of NADW was likely confined to shallower depths, leaving more of the deep Atlantic filled with water masses originating primarily from around Antarctica (3)(4)(5).…”

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confidence: 99%

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Glacial ocean circulation and stratification explained by reduced atmospheric temperature

Jansen

2016

Proc. Natl. Acad. Sci. U.S.A.

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Earth's climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5-10 • C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.LGM | AMOC | stratification | cooling | sea-ice T he deep ocean today is ventilated mainly by two water masses. North Atlantic deep water (NADW) is formed in the North Atlantic before flowing southward at a depth of about 2-3 km and eventually rising back up to the surface in the Southern Ocean. Antarctic bottom water (AABW) is formed around Antarctica and spreads northward into the abyssal basins. The AABW that makes it into the Atlantic then slowly upwells into the lower NADW before returning southward and resurfacing again around Antarctica (1, 2). The glacial equivalent of NADW was likely confined to shallower depths, leaving more of the deep Atlantic filled with water masses originating primarily from around Antarctica (3-5). Moreover, the two water masses appear more distinct, with less mixing between them (6).Multiple studies have pointed toward the potential importance of sea ice and surface buoyancy fluxes around Antarctica in controlling changes in the deep ocean stratification and circulation between the present and Last Glacial Maximum (LGM) (7-11). Specifically, we recently showed that enhanced buoyancy loss around Antarctica is expected to lead to an increase in the abyssal stratification, an upward shift of NADW, and a clearer separation between NADW and southward-flowing AABW (11)-all in agreement with inferences made for differences in circulation and stratification between the present and LGM (3,6,12,13). This gives rise to the hypothesis that strong cooling around Antarctica led to an increased net freezing...

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“…(SV) and −5.2 SV are roughly consistent with the observed rate of NADW formation and the transport of AABW into the North Atlantic (1,2).…”

Section: Significancesupporting

confidence: 68%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Glacial ocean circulation and stratification explained by reduced atmospheric temperature

Jansen

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Talley (30) gives an excellent review of our current understanding of the pathways of the overturning circulation in the global ocean based on estimates of the heat, freshwater, and nutrient transports. The schematic in Fig.…”

Section: Significancementioning

confidence: 99%

Antarctic sea ice control on ocean circulation in present and glacial climates

Ferrari

Jansen

Adkins

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

342

502

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Significance The ocean’s role in regulating atmospheric carbon dioxide on glacial–interglacial timescales remains an unresolved issue in paleoclimatology. Many apparently independent changes in ocean physics, chemistry, and biology need to be invoked to explain the full signal. Recent understanding of the deep ocean circulation and stratification is used to demonstrate that the major changes invoked in ocean physics are dynamically linked. In particular, the expansion of permanent sea ice in the Southern Hemisphere results in a volume increase of Antarctic-origin abyssal waters and a reduction in mixing between abyssal waters of Arctic and Antarctic origin.

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“…That core idea is based on a large body of research. [1][2][3] Rather than warming as it ascends as Kininmonth claims, the cold, dense water warms primarily at the surface as it travels northward out of the Southern Ocean. The dynamics of the oceanic overturning circulation leads to a cooling, not warming, of the atmosphere in response to a slowdown of the overturning.…”

mentioning

confidence: 99%