The role of oceans and sea ice in abrupt transitions between multiple climate states

Rose, B. E. J., Ferreira, D. ORCID: https://orcid.org/0000-0003-3243-9774 and Marshall, J. (2013) The role of oceans and sea ice in abrupt transitions between multiple climate states. Journal of Climate, 26 (9). pp. 2862-2879. ISSN 1520-0442 doi: 10.1175/JCLI-D-12-00175.1

Abstract/Summary

The coupled climate dynamics underlying large, rapid, and potentially irreversible changes in ice cover are studied. A global atmosphere–ocean–sea ice general circulation model with idealized aquaplanet geometry is forced by gradual multi-millennial variations in solar luminosity. The model traverses a hysteresis loop between warm ice-free conditions and cold glacial conditions in response to ±5 W m−2 variations in global, annual-mean insolation. Comparison of several model configurations confirms the importance of polar ocean processes in setting the sensitivity and time scales of the transitions. A “sawtooth” character is found with faster warming and slower cooling, reflecting the opposing effects of surface heating and cooling on upper-ocean buoyancy and, thus, effective heat capacity. The transition from a glacial to warm, equable climate occurs in about 200 years. In contrast to the “freshwater hosing” scenario, transitions are driven by radiative forcing and sea ice feedbacks. The ocean circulation, and notably the meridional overturning circulation (MOC), does not drive the climate change. The MOC (and associated heat transport) collapses poleward of the advancing ice edge, but this is a purely passive response to cooling and ice expansion. The MOC does, however, play a key role in setting the time scales of the transition and contributes to the asymmetry between warming and cooling.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/33167
Item Type	Article
Refereed	Yes
Divisions	No Reading authors. Back catalogue items Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Uncontrolled Keywords	Sea ice, Atmosphere-ocean interaction, Meridional overturning circulation, Heat budgets/fluxes, Ice loss/growth, Coupled models
Publisher	American Meteorological Society
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