Speaker – Kay McMonigal, MEAS, Atmospheric Sciences (host- S. Larson)

Seminar Title – Convergent ocean heat transport drives recent Indian Ocean warming

Abstract – Since 2000, the Indian Ocean has warmed more rapidly than the other ocean basin. This warming has climate impacts relevant for the one third of the human population living in Indian Ocean rim countries. We aim to understand the dynamics behind the recent warming, to better predict future warming patterns. Any change in ocean heat content over time is the sum of air-sea fluxes and ocean heat advection. Because air-sea fluxes alone cannot explain the rapid warming, we focus on the convergence of ocean heat transport. We estimate a two year time series of Indian Ocean heat transport and convergence from observations, and compare it to snapshot estimates from 1987, 2002, and 2009. The Indian Ocean converged heat over the previous decade, a significant change from earlier estimates. The ocean heat convergence is the same magnitude as the observed warming, implying air-sea fluxes are near zero. Independent air-sea flux products corroborate this. We find that the warming was caused approximately equally by changes to the Indonesian Throughflow and the South Indian Ocean gyre. This implies that the expected future reduction in Indonesian Throughflow transport may not slow the rapid warming. With appropriate boundary current measurements, this method can be applied to other ocean basins. These observational estimates can also be used to validate air-sea flux products and ocean reanalyses.

Please check your email for the Zoom link.