Glacial reduction and millennial-scale variations in Drake Passage throughflow
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Date
2015-11-03
Journal Title
Journal ISSN
Volume Title
Publisher
National Academy of Sciences
Abstract
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.
Description
Keywords
Ciencia, Paleoceanography, Glacial–interglacial changes, Sedimentology, Antarctic Circumpolar Current
Citation
PNAS November 3, 2015 . vol. 112 , no. 44 , 13497