Impact of the Antarctic topography on meridional energy transport and its consequential effect in the monsoon circulation

Antarctica has been losing ice in the past, and its ice loss is projected to further enhance in the future due to global warming, causing orographic changes over the region. Such orographic changes are likely to profoundly influence the global climate systems through energy transport over the Southern Hemisphere. The South Asian monsoon system, an anomalous climate system (a transient eddy regionally occurring rigorously during JJAS) originating in the Southern Hemisphere and transporting anomalous energy towards higher latitudes, is also expected to get influenced by its orography. A coupled global climate modelling framework is therefore used in this study to investigate the potential influence of the Antarctic orography on the South Asian monsoon system. The investigation reveals that a reduction in the Antarctic elevation would cause warming over the continent, which will cause changes in the energy budget, with more outgoing long-wave radiation over Antarctica due to a warmer surface and moist atmosphere aloft. The global climate responds to this perturbation by enhancing the southward energy transport primarily by the atmospheric component via changes in mean flow and eddies from the equatorial region all the way to the South Pole. The monsoon system supports this southward energy transport demand in the Southern Hemisphere by strengthening the mean meridional circulation in the three cells over the Indian Ocean sector. Due to this, the low-level cross-equatorial flow enhances over the south equatorial Indian Ocean, which increases the evaporation, and causes changes in precipitation and stationary wave patterns. The sea-level pressure and surface temperature changes adjust accordingly in response to changes in the circulation. However, rainfall and circulation over the Asian landmass do not change much as the southward energy transport is very much less and is mostly supported by the oceanic components and changes in latent energy over these latitudes.