Tropical rainfall patterns driven by reduced sea ice in high boreal latitudes

摘要

Satellite data enabled the Intergovernmental Panel on Climate Change (IPCC), through Report V, to indicate that the regional distribution of sea ice has been reducing in the Northern hemisphere high latitudes. This study assimilated that reduction into a general circulation model of intermediate complexity to simulate the tropical rainfall response. The Northern hemisphere tropospheric wind field simulations presented a clear similarity to the Northern Annular Mode negative phase. In particular, the meridional wind anomalies of the Northern hemisphere Ferrel cell suggest that the energy upsurge due to the boreal sea ice decrease results in an increase in the amplitude of the Rossby waves, thus connecting the polar zone to the tropics. The 500 hPa vertical motion and the rainfall distribution in the tropical belt simulations show a southward displacement of the Atlantic Intertropical Convergence Zone and also the South Atlantic Convergence Zone. Although several studies indicate the Intertropical Convergence Zone is shifted towards the hemisphere most heated by climatic variations, the apparent disagreement with our results can be understood by considering that some continental sectors in the Northern Hemisphere mid-latitudes have shown cooling in recent years, probably in response to the boreal sea ice decrease.