Summary: Climate Dynamics manuscript No.
(will be inserted by the editor)
Multiple sea-ice states and abrupt MOC transitions in
a general circulation ocean model
Yosef Ashkenazy · Martin Losch · Hezi
Gildor · Dror Mirzayof · Eli Tziperman
Received: date / Accepted: date
Abstract Sea ice has been suggested, based on simple models, to play an impor-
tant role in past glacial-interglacial oscillations via the so-called "sea-ice switch"
mechanism. An important consequence of this mechanism is that multiple sea-ice
extents can exist under the same land ice configuration. Here we use a state-
of-the-art ocean general circulation model coupled to an atmospheric energy-
moisture-balance model to test this hypothesis. The model includes a dynamic-
thermodynamic sea-ice module, has a realistic ocean configuration and bathymetry,
and is forced by annual mean forcing. We performed several runs under two dif-
ferent land ice distributions representing present day and cold climate conditions.
In each case the ocean model is initiated with both ice-free and fully ice-covered
states. The present day runs converge approximately to the same state, while the
cold climate runs converge to different final sea ice states. In these states, sea-ice
extents are different by up to four degrees in latitude in both hemispheres. While