Re-evaluating Antarctic sea-ice variability and its teleconnections in a GISS global climate model with improved sea ice and ocean processes

摘要

This study re-evaluated simulated Antarctic sea-ice variability and its teleconnections in a NASA Goddard Institute for Space Studies (GISS) coupled global climate model (CGCM) with improved sea-ice and ocean processes. With the improvements to the parameterizations of sea-ice dynamics and thermodynamics and of sub-grid-scale ocean processes, the new version of the GISS/CGCM does indeed do a better job in the representations of the local/regional ice-ocean interactions with regard to (1) the seasonal distributions of the Antarctic sea-ice edges (SIE), and (2) the vertical temperature and salinity structure in the upper Southern Ocean and surface air temperature (SAT) climatology in the southern high latitudes compared with the control version. However, these encouraging local/regional improvements do not extend to the simulations of the polar and extrapolar climate teleconnections. There is no obvious change to the simulations of the dominant spatial covarying patterns of the SAT variability on either the regional (southern high latitudes) or global scales. The simulated teleconnections between Antarctic SIE and global SAT still show the weak El Ni?o-southern oscillation like correlation pattern in the eastern tropical Pacific, though the new version generates a stronger tropical Indian component. Some dominant observed teleconnection patterns in the western extreme of the tropical Pacific and over the tropical continents (in-phase relationship between tropical South America and Africa) are still not well represented or are missed in the Antarctic SIE and global SAT lead/lag correlation maps and the empirical orthogonal function analysis on those correlation maps. The possible causes of the weak teleconnections in the improved GISS/CGCM are briefly discussed.