Glacial reduction and millennial-scale variations in Drake Passage throughflow

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 wa...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences
Main Authors: Lamy, Frank, Arz, Helge W., Kilianc, Rolf, Lange, Carina B., Lembke-jene, Lester, Wengler, Marc, Kaiser, Jerome, Baeza-urrea, Oscar, Hall, Ian R., Harada, Naomi, Tiedemann, Ralf
Format: Text
Language:English
Published: Natl Acad Sciences
Subjects:
geo
envir
Antarctic
Drake Passage
Indian
Pacific
Scotia Sea
Southern Ocean
The Antarctic
Antarc*
Sea ice
Online Access:https://doi.org/10.1073/pnas.1509203112
https://archimer.ifremer.fr/doc/00351/46233/46119.pdf
https://archimer.ifremer.fr/doc/00351/46233/
Description
Summary: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 similar 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.

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