| Abstract | During Snowball Earth episodes of the Neoproterozoic and Paleoproterozoic,limited amounts of tropical open ocean (Jormungand), or tropical ocean withthin ice cover, would help to explain (1) vigorous glacial activity in lowlatitudes, (2) survival of photosynthetic life, and (3) deglacial recoverywithout excessive buildup of atmospheric CO2. Some previous models havesuggested that tropical open ocean or thin-ice cover is possible; howeverits viability in the presence of kilometer-thick sea glaciers flowing fromhigher latitudes has not been demonstrated conclusively. Here we describe anew method of asynchronously coupling a zonal sea-glacier model with a 3-DGlobal Climate Model, and apply it to Snowball Earth. Equilibrium curves ofice line vs. CO2 are mapped out, as well as their dependence on ocean heattransport efficiency, sea-glacier flow, and other model parameters. No climatestates with limited tropical open ocean or thin ice are found in any of ourmodel runs, including those with sea glaciers. If this result is correct, thenother refugia such as cryoconite pans would have been required for life tosurvive. However, the reasons for the differences between our results andothers should first be resolved. It is suggested that small-scale convectivedynamics, affecting fractional snow cover in low latitudes, may be a criticalfactor accounting for these differences. |
