Southern Ocean warming delayed by circumpolar upwelling and equatorward transport
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Marshall_Southern ocean.pdf
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Author(s)
Armour, Kyle C.
Donohoe, Aaron
Newsom, Emily R.
Marshall, John C
Scott, Jeremy
Date Issued
May 2016
Journal
Nature Geoscience
Publisher
Nature Publishing Group
Citation
Armour, Kyle C., John Marshall, Jeffery R. Scott, Aaron Donohoe, and Emily R. Newsom. “Southern Ocean Warming Delayed by Circumpolar Upwelling and Equatorward Transport.” Nature Geoscience, vol. 9, no. 7, 2016, pp. 549–554.
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Author's final manuscript
Abstract
The Southern Ocean has shown little warming over recent decades, in stark contrast to the rapid warming observed in the Arctic. Along the northern flank of the Antarctic Circumpolar Current, however, the upper ocean has warmed substantially. Here we present analyses of oceanographic observations and general circulation model simulations showing that these patterns—of delayed warming south of the Antarctic Circumpolar Current and enhanced warming to the north—are fundamentally shaped by the Southern Ocean’s meridional overturning circulation: wind-driven upwelling of unmodified water from depth damps warming around Antarctica; greenhouse gas-induced surface heat uptake is largely balanced by anomalous northward heat transport associated with the equatorward flow of surface waters; and heat is preferentially stored where surface waters are subducted to the north. Further, these processes are primarily due to passive advection of the anomalous warming signal by climatological ocean currents; changes in ocean circulation are secondary. These findings suggest the Southern Ocean responds to greenhouse gas forcing on the centennial, or longer, timescale over which the deep ocean waters that are upwelled to the surface are warmed themselves. It is against this background of gradual warming that multidecadal Southern Ocean temperature trends must be understood.
MIT Department
Massachusetts Institute of Technology. Center for Global Change Science
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.1038/ngeo2731
