A 450-kyr record of hydrological conditions on the western Agulhas Bank Slope, south of Africa

Rau, A.; Rogers, John C.; Lütjeharms, J. R. E.; Giraudeau, Jacques; Lee‐Thorp, Julia A.; Chen, Min‐Te; Waelbroeck, C.

doi:10.1016/s0025-3227(01)00213-4

Cited by 88 publications

(81 citation statements)

References 47 publications

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“…As this species is strongly calcified and represents a warm-water and oligotrophic indicator [ Flores et al, 2003], their findings support our hypothesis for a stronger influence of the Agulhas Current into the Cape Basin earlier than 250 ka. A strong change in surface water conditions in the southeast Atlantic (warmer waters and more clearly defined glacial-interglacial cycles), based on shifts in planktonic foraminiferal assemblages and sediment composition, has also been found at approximately 200 -250 ka in core MD96-2080 [Rau et al, 2002], and linked by these authors to a decreased intensity of Agulhas ring shedding and associated subantarctic (cold) water intrusions. The more sustained periods of high SSTs during glacial times earlier than 250 ka at Site 1089 would thus indicate a stronger Agulhas influence into the subantarctic during this time compared to later glacials.…”

Section: Diverging Climatic Trends At 250 Kamentioning

confidence: 84%

“…We also discuss results from three additional sites for which a detailed reconstruction of the palaeoclimate evolution over several glacial-interglacial cycles is available. Site 980 [McManus et al, 1999] is located in the North Atlantic, core MD96-2080 [Rau et al, 2002] in the southeast Atlantic and core MD97-2120 [Pahnke and Zahn, 2005] in the southwest Pacific.…”

Section: S; 9°53mentioning

confidence: 99%

“…Blue arrows indicate d 13 C Cibicidoides minima right after climatic optimum conditions during interglacials. Important climatic events recognized at core site MD96-2080 [Rau et al, 2002] are also shown: Globorotalia menardii accumulation rate peaks at 22, 139, and 258 ka (red arrows), and relative abundances of Neogloboquadrina pachyderma (dextral) higher than 20% (blue horizontal bars), see text for discussion. The North Atlantic cooling event C21, at 82-85 ka (terminology after Chapman and Shackleton [1999]) is also highlighted.…”

Section: Palaeo-sst Reconstructionmentioning

confidence: 99%

“…Currently at about 40°S, the STF location is linked to southern Indian Ocean circulation patterns, and a STF equatorward shift by 4°latitude would altogether prevent Agulhas Current spillage into the Atlantic Ocean, and thus alter the interocean heat budget. There is however debate regarding the intensity of the Agulhas Current during the Last Glacial, as some authors [Prell et al, 1980;Winter and Martin, 1990;Flores et al, 1999;Rau et al, 2002;Gersonde et al, 2003a;Esper et al, 2004] support either uninterrupted or seasonally modulated heat transfer from low to high latitudes, while others [Berger and Vincent, 1986;McIntyre et al, 1989] suggest it did not retroflect during glacial times. Peeters et al [2004] show how the Agulhas spillage shifts from a strong reduction during midglacial times to a vigorous flow during late glacials.…”

Section: Introductionmentioning

confidence: 99%

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The last five glacial‐interglacial transitions: A high‐resolution 450,000‐year record from the subantarctic Atlantic

2007

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[1] A submillennial resolution, radiolarian-based record of summer sea surface temperature (SST) documents the last five glacial to interglacial transitions at the subtropical front, southern Atlantic Ocean. Rapid fluctuations occur both during glacial and interglacial intervals, and sudden cooling episodes at glacial terminations are recurrent. Surface hydrography and global ice volume proxies from the same core suggest that summer SST increases prior to terminations lead global ice-volume decreases by 4.7 ± 3.7 ka (in the eccentricity band), 6.9 ± 2.5 ka (obliquity), and 2.7 ± 0.9 ka (precession). A comparison between SST and benthic d 13 C suggests a decoupling in the response of northern subantarctic surface, intermediate, and deep water masses to cold events in the North Atlantic. The matching features between our SST record and the one from core MD97-2120 (southwest Pacific) suggests that the super-regional expression of climatic events is substantially affected by a single climatic agent: the Subtropical Front, amplifier and vehicle for the transfer of climatic change. The direct correlation between warmer DT site at Vostok and warmer SST at ODP Site 1089 suggests that warmer oceanic/ atmospheric conditions imply a more southward placed frontal system, weaker gradients, and therefore stronger Agulhas input to the Atlantic Ocean.Citation: Cortese, G., A. Abelmann, and R. Gersonde (2007), The last five glacial-interglacial transitions: A high-resolution 450,000-year record from the subantarctic Atlantic, Paleoceanography, 22, PA4203,

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Section: Diverging Climatic Trends At 250 Kamentioning

confidence: 84%

Section: S; 9°53mentioning

confidence: 99%

Section: Palaeo-sst Reconstructionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The last five glacial‐interglacial transitions: A high‐resolution 450,000‐year record from the subantarctic Atlantic

2007

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“…It has been shown that this interocean leakage forms a crucial link in the climatically crucial global, thermohaline circulation (Gordon, 1986). Based on a palaeo-climatological investigation it has even recently been demonstrated (Peeters et al, 2004) that this inter-ocean leakage has been particularly strong at the end of each of the last five glacial periods, but that it has never been absent entirely (Rau et al, 2002). Modelling studies by Weijer et al (1999Weijer et al ( , 2001Weijer et al ( , 2002 have in addition shown that a diminution in the exchange at the Agulhas retroflection leads inexorably to a slowing of the Atlantic Ocean's thermohaline overturning.…”

Section: Agulhas Retroflectionmentioning

confidence: 99%

Three decades of research on the greater Agulhas Current

Lütjeharms

2007

Ocean Sci.

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Abstract. The greater Agulhas Current has been shown to be a key link in the global thermohaline circulation and an increased understanding of this current system is therefore of more than just local interest. Knowledge on the Agulhas Current system has in fact increased enormously over the past 30 years. This review covers some aspects of what has been learnt on the northern and the southern parts of the Agulhas Current proper and their influence on the waters and circulation of the adjoining continental shelf. It also discusses the Natal Pulse and new information that has been gained on how it is triggered and what influence it has. It deals with the Agulhas retroflection, the shedding of Agulhas rings and the movement and characteristics of these rings that contributes to the meridional overturning circulation of the global ocean. The Agulhas Return Current forms part of the final outflow of the system and current knowledge on that current is appraised. The sources of the Agulhas Current have been a controversial subject for many years and this dispute continues. This is described and discussed, based on what information has been gained from research over the past three decades. Building on what is currently known, some suggestions are given on the most important remaining knowledge gaps and how these could most efficaciously be filled.

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Atlantic overturning responses to obliquity and precession over the last 3 Myr

Lisiecki

2014

Paleoceanography

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This study analyzes 39 Atlantic and seven Pacific benthic 13 C records to characterize obliquity and precession responses in Atlantic overturning since 3 Ma. Regional benthic 13 C stacks are also analyzed. A major transition in orbital responses is observed at 1.5-1.6 Ma coincident with the first glacial shoaling of Northern Component Water. Since ∼1.5 Ma, the phases of Atlantic benthic 13 C records from 2300 to 4000 m depth lag maximum obliquity by 59 • (6.7 kyr) and June perihelion precession forcing by 133 • (8.5 kyr). Comparison with North Atlantic sea surface temperature suggests that these orbital responses (particularly precession) in middle deep Atlantic 13 C are associated with changes in ocean heat transport and overturning rates. The mid-Pleistocene transition had little effect on the obliquity and precession phases of benthic 13 C but did result in a ∼50% decrease in the obliquity power of middle deep Atlantic 13 C at 0.6 Ma.

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A 450-kyr record of hydrological conditions on the western Agulhas Bank Slope, south of Africa

Cited by 88 publications

References 47 publications

The last five glacial‐interglacial transitions: A high‐resolution 450,000‐year record from the subantarctic Atlantic

The last five glacial‐interglacial transitions: A high‐resolution 450,000‐year record from the subantarctic Atlantic

Three decades of research on the greater Agulhas Current

Atlantic overturning responses to obliquity and precession over the last 3 Myr

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