HR: 0830h
AN: GC31B-0189    [PDF]
TI: Multiple Equilibria in CCM 3.6.6 Coupled to the Oceanic Mixed Layer with Thermodynamic sea ice.
AU: Langen, P L
EM: plangen@gfy.ku.dk
AF: Niels Bohr Institute for Astronomy, Physics and Geophysics, Juliane Maries vej 30,, Copenhagen Oe, 2100 Denmark
AU: * Alexeev, V A
EM: valexeev@iarc.uaf.edu
AF: International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Drive, PO Box 757340,, Fairbanks, AK 99775 United States
AB: An atmospheric GCM (Climate Community Model, CCM 3.6.6) is coupled to an upper mixed-layer ocean with thermodynamic sea ice on an aquaplanet. An annually averaged diurnal cycle of insolation is used such that effects of seasonality are neglected. Sea ice is modeled by a simple four-layer thermodynamic sea ice model coupled to the atmosphere-ocean system. A simple form of heat flux to the mixed-layer from below, the so called "Q-flux", is constructed and introduced into the model. All externally specified fields, such as the insolation, the Q-flux, the ozone concentration and the mixed layer depth (50m uniformly), are constant overthe year, zonally symmetric and symmtric about the Equator. The Q-flux can be viewed as a crude representation of the poleward oceanic heat transport and thus takes on negative values at low latitudes and positive values at high latitudes. While the shape of the Q-flux is kept constant various choices of its amplitude are used and the model is run to equilibrium for each choice. The outcome of this ranges from very icy climates, with sea ice margins in both hemispheres at 35 degrees, to completely ice-free climates. Between these extremes arises a complex transition which includes both asymmetric climates, with sea ice in one hemisphere and no sea ice in the other, and multiple equilibria, where sea ice at both low and high latitudes are possible under the same external forcing.
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
DE: 3210 Modeling
DE: 3319 General circulation
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting