Cross-basin ocean-atmosphere interactions in radiatively-induced climate change

Anthropogenic aerosols are an important forcing for climate change during the instrumental era, notably the prolonged African Sahel drought of the 1950s-80s and the slow recovery after the late 1980s. Although the radiative forcing induced by anthropogenic changes in greenhouse gases and aerosols is distinct in spatial distribution, earlier studies indicate that because of coupled ocean-atmospheric feedbacks, regional patterns of climate change are somewhat similar in response to each of the forcing types. Following the erection of clean air acts in North America and Europe, anthropogenic aerosols declined in these regions after the 1980s while increasing over Asia. We investigate the coupled ocean-atmospheric response to a zonal shift in radiative cooling from North America to Asia. For simplicity, we keep the forcing magnitude and latitude the same.

The response shares some common characteristics between North American and Asian forcings, including an accelerated Atlantic meridional overturning circulation. In addition to the “trivial” local cooling, the North American and Asian forcing results in marked differences in regional climate response, e.g., in the wind-driven shallow overturning circulation. Coupled ocean-atmosphere interactions across ocean basins are important in the pattern formation, including Bjerknes feedback in zonal SST variations and wind-evaporation-SST (WES) feedback in the trade-wind regime. Global response to radiative forcing offers a different perspective of cross-basin ocean-atmosphere interactions.