Interannual-decadal sea-ice variability and predictability over the Weddell Sea

Abstract:

Potential sources of interannunal-decadal sea-ice variability and predictability over the Weddell Sea are investigated with a series of coupled general circulation model experiments. The model results corroborate the observational fact that interannual variations of sea-ice concentration (SIC) over the Weddell Sea are associated with atmospheric teleconnection from the tropical Pacific climate variability; El-Niño Southern Oscillation (ENSO). When the model’s sea-surface temperature (SST) in the tropics is nudged to its monthly climatology, the SIC variations occur through local air-sea-ice interaction under the influence of the internal atmospheric variability, Southern Annular Mode (SAM). The important role of local air-sea-ice interaction is further demonstrated in the seasonal reforecast experiments that the SIC initialization adds positive values to prediction skills over the Weddell Sea by improving the local atmospheric variability. On the other hand, decadal variations of the SIC over the Weddell Sea are accompanied by atmospheric teleconnection from the SAM and the tropical Pacific climate variability, i.e., the Interdecadal Pacific Oscillation (IPO). When the model’s SST outside the Weddell Sea is nudged to its monthly climatology, the SIC variations occur through changes in upper-ocean salinity, and hence the horizontal advection, indicating a role of local ice-ocean interaction. These results suggest that skillful predictions of decadal sea-ice variability over the Weddell Sea require accurate initialization of sea-ice and subsurface ocean conditions in the model.