Increased glacial-age ventilation of the Chilean margin by Antarctic Intermediate Water

Muratli, Jesse M; Chase, Zanna; Mix, Alan C; McManus, James

doi:10.1038/ngeo715

Cited by 61 publications

(79 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Strongly reduced CHC vigor and more sluggish DP transport during the LGM would plausibly decrease the export of Pacific surface and intermediate water masses into the South Atlantic and thus, reduce the cold water route contribution. Such glacial Southern Ocean circulation is in accordance with a stronger South Pacific Gyre and the export of well-oxygenated AAIW along the Chilean margin (32,33). Concurrently, proxy data indicate poorly ventilated intermediate waters in the glacial South Atlantic as contributions from the Pacific and Indian Oceans were reduced (34), consistent with reduced export from the major modern intermediate water formation region in the Southeast Pacific through the DP (Fig.…”

Section: Resultssupporting

confidence: 57%

Glacial reduction and millennial-scale variations in Drake Passage throughflow

Lamy

Arz

Kilian

et al. 2015

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

114

111

View full text Add to dashboard Cite

The Drake Passage (DP) is the major geographic constriction for the Antarctic Circumpolar Current (ACC) and exerts a strong control on the exchange of physical, chemical, and biological properties between the Atlantic, Pacific, and Indian Ocean basins. Resolving changes in the flow of circumpolar water masses through this gateway is, therefore, crucial for advancing our understanding of the Southern Ocean’s role in global ocean and climate variability. Here, we reconstruct changes in DP throughflow dynamics over the past 65,000 y based on grain size and geochemical properties of sediment records from the southernmost continental margin of South America. Combined with published sediment records from the Scotia Sea, we argue for a considerable total reduction of DP transport and reveal an up to ∼40% decrease in flow speed along the northernmost ACC pathway entering the DP during glacial times. Superimposed on this long-term decrease are high-amplitude, millennial-scale variations, which parallel Southern Ocean and Antarctic temperature patterns. The glacial intervals of strong weakening of the ACC entering the DP imply an enhanced export of northern ACC surface and intermediate waters into the South Pacific Gyre and reduced Pacific–Atlantic exchange through the DP (“cold water route”). We conclude that changes in DP throughflow play a critical role for the global meridional overturning circulation and interbasin exchange in the Southern Ocean, most likely regulated by variations in the westerly wind field and changes in Antarctic sea ice extent.

show abstract

Section: Resultssupporting

confidence: 57%

Glacial reduction and millennial-scale variations in Drake Passage throughflow

Lamy

Arz

Kilian

et al. 2015

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

114

111

View full text Add to dashboard Cite

show abstract

“…These precisely dated palaeoceanographic records indicate a strong correlation between SO upwelling events and the deglacial atmospheric CO 2 rise, providing strong support for the SO upwelling hypothesis. The R surf reconstructions also help to reveal a deglacial ageing of AAIW that is consistent with its reduction in oxygen concentration 14 , indicating that deglacial CO 2 excess was spread, at least partly, via an AAIW pathway.…”

mentioning

confidence: 80%

“…To establish the chronology of the core, we used 24 14 C ages on planktic foraminifera corrected with the R surf age determined from the tephra layers (Fig. 2f).…”

Section: Resultsmentioning

confidence: 99%

“…2f). Then, the R surf -corrected planktic 14 C dates were calibrated using the OxCal software 25 28 and varved lake sediments 29 . 14 C data and R surf estimates are reported in Supplementary Tables S1,S2.…”

Section: Resultsmentioning

confidence: 99%

“…This so-called SO upwelling hypothesis remains a controversial issue. On one hand, records from intermediate depths in the South East Pacific (SEP) have shown a reduction in Antarctic Intermediate Water (AAIW) oxygen concentration during the deglacial warming period, which may be linked with an upwelling of low oxygen waters at the SO divergence, which are transported northward via AAIW 14 . On the other hand, 14 C records from the South Pacific do not indicate any deglacial 14 C depletion at intermediate depths off Chile and New Zealand 11,13 , which does not support the SO upwelling hypothesis.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Carbon isotope records reveal precise timing of enhanced Southern Ocean upwelling during the last deglaciation

et al. 2013

View full text Add to dashboard Cite

International audienceThe Southern Ocean plays a prominent role in the Earth’s climate and carbon cycle. Changes in the Southern Ocean circulation may have regulated the release of CO₂ to the atmosphere from a deep-ocean reservoir during the last deglaciation. However, the path and exact timing of this deglacial CO₂ release are still under debate. Here we present measurements of deglacial surface reservoir ¹⁴C age changes in the eastern Pacific sector of the Southern Ocean, obtained by ¹⁴C dating of tephra deposited over the marine and terrestrial regions. These results, along with records of foraminifera benthic–planktic ¹⁴C age and δ¹³C difference, provide evidence for three periods of enhanced upwelling in the Southern Ocean during the last deglaciation, supporting the hypothesis that Southern Ocean upwelling contributed to the deglacial rise in atmospheric CO₂. These independently dated marine records suggest synchronous changes in the Southern Ocean circulation and Antarctic climate during the last deglaciation

show abstract

Different mechanisms of silicic acid leakage and their biogeochemical consequences

2014

View full text Add to dashboard Cite

In the modern ocean, silicic acid is effectively trapped in the Southern Ocean. According to the silicic acid leakage hypothesis, a loosening of this trapping may have contributed to low atmospheric CO 2 during glacial times. Using a model with dynamical feedbacks in ocean physics and biology, we explore three distinct mechanisms to loosen the trapping and trigger silicic acid leakage from the Southern Ocean: sea ice expansion, weaker winds, and iron addition. The basic idea of the iron addition mechanism was previously explored using a simple box model. Here we confirm the main results of the earlier work and demonstrate further that sea ice expansion and weaker southern westerlies can also trigger silicic acid leakage. The three mechanisms are not mutually exclusive, and their biogeochemical consequences are dissimilar in terms of the spatial patterns of Si:N uptake and the relative changes in opal and particulate organic carbon fluxes both in and outside the Southern Ocean. While it is not entirely clear how sea ice, winds, and iron deposition were different during the last glacial period compared to today, we examine the synergistic effects of these three triggers in one simulation. In this simulation, the combination of sea ice and iron reproduces the north-south dipole of productivity recorded in export production proxies, but effects of the iron perturbation seem to dominate the overall biogeochemical response.

show abstract

Increased glacial-age ventilation of the Chilean margin by Antarctic Intermediate Water

Cited by 61 publications

References 27 publications

Glacial reduction and millennial-scale variations in Drake Passage throughflow

Glacial reduction and millennial-scale variations in Drake Passage throughflow

Carbon isotope records reveal precise timing of enhanced Southern Ocean upwelling during the last deglaciation

Different mechanisms of silicic acid leakage and their biogeochemical consequences

Contact Info

Product

Resources

About