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PALEOCEANOGRAPHY, VOL. 21, PA2005, doi:10.1029/2005PA001154, 2006

Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages

J. R. Toggweiler

Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, New Jersey, USA


Joellen L. Russell

Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, New Jersey, USA


S. R. Carson

Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, New Jersey, USA


Abstract

An idealized general circulation model is constructed of the ocean's deep circulation and CO2 system that explains some of the more puzzling features of glacial-interglacial CO2 cycles, including the tight correlation between atmospheric CO2 and Antarctic temperatures, the lead of Antarctic temperatures over CO2 at terminations, and the shift of the ocean's δ13C minimum from the North Pacific to the Atlantic sector of the Southern Ocean. These changes occur in the model during transitions between on and off states of the southern overturning circulation. We hypothesize that these transitions occur in nature through a positive feedback that involves the midlatitude westerly winds, the mean temperature of the atmosphere, and the overturning of southern deep water. Cold glacial climates seem to have equatorward shifted westerlies, which allow more respired CO2 to accumulate in the deep ocean. Warm climates like the present have poleward shifted westerlies that flush respired CO2 out of the deep ocean.

Received 14 March 2005; accepted 18 January 2006; published 27 April 2006.

Keywords: carbon cycle; ocean circulation; ice ages.

Index Terms: 1615 Global Change: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912); 3344 Atmospheric Processes: Paleoclimatology (0473, 4900); 4532 Oceanography: Physical: General circulation (1218, 1222); 4930 Paleoceanography: Greenhouse gases; 4946 Paleoceanography: Milankovitch theory.

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Citation: Toggweiler, J. R., J. L. Russell, and S. R. Carson (2006), Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages, Paleoceanography, 21, PA2005, doi:10.1029/2005PA001154.