Abstract
<strong class="journal-contentHeaderColor">Abstract.</strong> The effect of sea-ice on various aspects of the Southern Hemisphere (SH) extratropical climate is examined. Two simulations using the LMD GCM are performed: a control run with the observed sea-ice distribution and an anomaly run in which all SH sea-ice is replaced by open ocean. When sea-ice is removed, the mean sea level pressure displays anomalies predominantly negatives near the Antarctic coast. In general, the meridional temperature gradient is reduced over most of the Southern Ocean, the polar jet is weaker and the sea level pressure rises equatorward of the control ice edge. The high frequency filtered standard deviation of both the sea level pressure and the 300-hPa geopotential height decreases over the southern Pacific and southwestern Atlantic oceans, especially to the north of the ice edge (as prescribed in the control). In contrast, over the Indian Ocean the perturbed simulation exhibits less variability equatorward of about 50°S and increased variability to the south. The zonal averages of the zonal and eddy potential and kinetic energies were evaluated. The effect of removing sea-ice is to diminish the available potential energy of the mean zonal flow, the available potential energy of the perturbations, the kinetic energy of the growing disturbances and the kinetic energy of the mean zonal flow over most of the Southern Ocean. The zonally averaged intensity of the subpolar trough and the rate of the baroclinic energy conversions are also weaker.<br><br><b>Key words. </b>Air-sea interactions · Meteorology and atmospheric dynamics (climatology; ocean · atmosphere interactions)
Highlights
There has been a statistically signi®cant increase in temperature since the mid-1940s in some regions of the Antarctic periphery (Harangozo et al, 1994; Turner et al, 1997)
The high latitudes of the Southern Hemisphere (SH) are a sensitive region of the globe where perturbation experiments to large-scale modi®cations of the climatic boundary conditions show a major response
Sea-ice is often thought to play a dominant role in this high-latitude response
Summary
There has been a statistically signi®cant increase in temperature since the mid-1940s in some regions of the Antarctic periphery (Harangozo et al, 1994; Turner et al, 1997). In order to understand the model sensitivity and to assess the possible impact of a climatic change it is useful to study how the melting of sea-ice, and the corresponding warming of the surface temperature, may aect the extratropical circulation of the Southern Hemisphere (hereafter SH). These circulation changes are related to basic characteristics such as the atmospheric energy cycle and the storm tracks.
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