Holocene shifts of the southern westerlies across the South Atlantic

Voigt, Ines; Chiessi, Cristiano Mazur; Prange, Matthias; Mulitza, Stefan; Groeneveld, Jeroen; Varma, Vidya; Henrich, Rüdiger

doi:10.1002/2014pa002677

Cited by 59 publications

(63 citation statements)

References 66 publications

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“…While the paleo‐SST data from cores in the southwest Pacific Ocean during the glacial period (25–21 ka) provide a fairly consistent picture of a northward STFZ and a stronger DSTF, results from the Holocene period are highly variable and contradictory (see sections 4.1 and 4.2) and do not agree with other regions of the Southern Ocean [ Bianchi and Gersonde , ; Moros et al ., ; Lamy et al ., ; Voigt et al ., ]. This may be due to the highly variable nature of the STFZ and the weaker SST gradients (~1°C/100 km) that are difficult to determine when there are large errors on the paleo‐SST data.…”

Section: Discussionmentioning

confidence: 99%

Changes in the position of the Subtropical Front south of New Zealand since the last glacial period

et al. 2015

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This study fills an important gap in our understanding of past changes in the Southern Subtropical Front (S-STF) in the southwest Pacific Ocean. Paleo-sea surface temperatures (SST) were estimated from planktic foraminiferal census counts from cores straddling the modern S-STF in the Solander Trough, south of New Zealand. The estimated SST were compared for 6 time slices; glacial period (25-21 ka), Last Glacial Maximum (LGM; 21-18 ka), early deglaciation (18-16 ka), late deglacial/early Holocene period (14-8 ka), mid-Holocene period (8-4 ka), and late Holocene period (4-0 ka). The position of the S-STF was determined by two methods:(1) the location of the 10°C isotherm and (2) the location of the highest SST gradients. These new results suggest that the S-STF was not continuous between east and west of New Zealand during the glacial period. Steep SST gradients indicate that a strong S-STF rapidly shifted south during the LGM and early deglaciation. During the late deglacial and Holocene periods the position of the S-STF differs between the two methods with reduced SST gradients, suggesting a more diffuse S-STF in the Solander Trough at this time. The glacial SST data suggest that the S-STF shifted north to the west of New Zealand, while to the east there was a stronger SST gradient across the front. This was possibly the result of an increased wind stress curl, which could have been caused by stronger, or more northerly Southern Hemisphere westerly winds (SHWW), or a merging of the SHWW split jet in this region.

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Section: Discussionmentioning

confidence: 99%

Changes in the position of the Subtropical Front south of New Zealand since the last glacial period

et al. 2015

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“…(c) Stable oxygen isotope data of Globorotalia inflata (sea level corrected) for sediment core GeoB13862‐1 (38.0°S, 53.7°W; 3588 m) on the Argentine margin. A lower δ 18 O represents a more southerly position of the Brazil‐Malvinas Confluence, and an inferred more southerly position of the Southern Hemisphere westerlies [ Voigt et al , ]. (d) Sea surface temperature reconstruction from GeoB3313‐1 (41.0°S, 74.5°W; 852 m), where warmer temperatures represent a lesser influence of cooler subpolar surface waters [ Lamy et al , ].…”

Section: Discussionmentioning

confidence: 99%

Antarctic intermediate water circulation in the South Atlantic over the past 25,000 years

et al. 2016

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Antarctic Intermediate Water is an essential limb of the Atlantic meridional overturning circulation that redistributes heat and nutrients within the Atlantic Ocean. Existing reconstructions have yielded conflicting results on the history of Antarctic Intermediate Water penetration into the Atlantic across the most recent glacial termination. In this study we present leachate, foraminiferal, and detrital neodymium isotope data from three intermediate‐depth cores collected from the southern Brazil margin in the South Atlantic covering the past 25 kyr. These results reveal that strong chemical leaching following decarbonation does not extract past seawater neodymium composition in this location. The new foraminiferal records reveal no changes in seawater Nd isotopes during abrupt Northern Hemisphere cold events at these sites. We therefore conclude that there is no evidence for greater incursion of Antarctic Intermediate Water into the South Atlantic during either the Younger Dryas or Heinrich Stadial 1. We do, however, observe more radiogenic Nd isotope values in the intermediate‐depth South Atlantic during the mid‐Holocene. This radiogenic excursion coincides with evidence for a southward shift in the Southern Hemisphere westerlies that may have resulted in a greater entrainment of radiogenic Pacific‐sourced water during intermediate water production in the Atlantic sector of the Southern Ocean. Our intermediate‐depth records show similar values to a deglacial foraminiferal Nd isotope record from the deep South Atlantic during the Younger Dryas but are clearly distinct during the Last Glacial Maximum and Heinrich Stadial 1, demonstrating that the South Atlantic remained chemically stratified during Heinrich Stadial 1.

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“…We also present the carbon isotope composition (δ 13 C) of the same species. Previous studies have applied the geochemical composition of G. inflata to reconstruct past thermocline conditions, the migration of midlatitude oceanic fronts, and the carbon isotopic composition of the SACW (Campos et al, ; Chiessi et al, ; Voigt et al, ). For every sample, between 5 and 10 shells of G. inflata from the 250–300 μm size fraction were handpicked under a stereomicroscope.…”

Section: Methodsmentioning

confidence: 99%

The Impact of the AMOC Resumption in the Western South Atlantic Thermocline at the Onset of the Last Interglacial

Santos

Lessa

Venancio

et al. 2017

Geophysical Research Letters

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After glacial terminations, large amounts of heat and salt were transferred from low to high latitudes, which is a crucial phenomenon for the reestablishment of the Atlantic Meridional Overturning Circulation (AMOC). However, how different glacial terminations evolved in the (sub)tropics is still poorly documented. Here we use foraminifera oxygen (δ18O) and carbon (δ13C) stable isotopes to show that the North Atlantic heat piracy, following the AMOC resumption at the early Last Interglacial, affected the thermocline δ18O levels of the subtropical western South Atlantic. Because of the cooling imposed by this process, glacial δ18O persisted in the thermocline for ~7 kyr after the onset of the Last Interglacial, dampening the effect of sea level rise usually imprinted on foraminifera δ18O during terminations. Faunal composition and δ13C also suggest the existence of a colder and thicker South Atlantic Central Water coeval with the AMOC recovery. This process apparently did not occur during the last deglaciation.

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Holocene shifts of the southern westerlies across the South Atlantic

Cited by 59 publications

References 66 publications

Changes in the position of the Subtropical Front south of New Zealand since the last glacial period

Changes in the position of the Subtropical Front south of New Zealand since the last glacial period

Antarctic intermediate water circulation in the South Atlantic over the past 25,000 years

The Impact of the AMOC Resumption in the Western South Atlantic Thermocline at the Onset of the Last Interglacial

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