Cooperative Institute for Research in Environmental Sciences

Special Seminar: The ocean's role in polar climate change

Special Seminar: The ocean's role in polar climate change

armor.jpgKyle Armour is a James S. McDonnell Foundation Postdoctoral Fellow in the Department of Earth, Atmospheric and Planetary Sciences at MIT. He obtained his PhD in the Department of Physics at the University of Washington in 2012. His main research interests are in climate dynamics, including the general circulation of the atmosphere and oceans, sea ice, and climate change. His recent work has spanned a range of topics including atmospheric feedbacks and climate sensitivity, the role of the oceans in setting the timescales and geographic patterns of climate change and variability, and the climate implications of geoengineering with stratospheric aerosols. During his PhD, he studied the potential for reversibility in the loss of Arctic sea ice and worked to quantify our climate commitment–the amount of warming that would still occur absent any future greenhouse gas or aerosol emissions. He is the recipient of a 2011 'Studying Complex Systems' Postdoctoral Fellowship Award from the James S. McDonnell Foundation.

Abstract: The retreat of Arctic sea ice has been one of the most striking features of climate change in recent decades, with the summer sea ice cover decreasing by about 40% since the 1980s. Accompanying this sea ice loss has been amplified warming in the Arctic, at a rate several time faster than the global mean. In stark contrast, the Antarctic sea ice cover has been steadily increasing over this period, consistent with an overall cooling of the Southern Ocean sea surface from the sea ice edge out to the Antarctic Circumpolar Current (the ACC, where substantial warming has occurred). Here I argue that interhemispheric asymmetries in the large-scale ocean circulation play a fundamental role in driving such distinct polar climate trends under greenhouse gas forcing: wind-driven upwelling around Antarctica acts to delay warming at the sea surface, while Arctic warming is accelerated by enhanced poleward ocean heat transport. I further discuss: (i) the extent to which these changes are a consequence of the background ocean circulation versus changes in circulation driven by the active nature of ocean heat uptake; (ii) a possible mechanism for the observed warming within the ACC region; and (iii) the role of internal climate variability in the observed Southern Ocean cooling and sea ice expansion.


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