Jie Ma, Ming Feng, Jian Lan, Dunxin Hu

Published in Geophysical Research Letters, February 2020

An ocean downscaling model product, forced under the Representative Concentration Pathway 8.5 future climate change scenario, has been used to understand the ocean heat balance of the Indian Ocean in a warming climate. Toward the end of the 21th century, the model simulates a significant reduction of Indonesian throughflow (ITF) transport, which reduces the Pacific to Indian Ocean heat transport by 0.20 PW, whereas across 32°S in the Southern Indian Ocean (SIO), the southward heat transport is reduced by 0.28 PW, mainly contributed from the weakening western boundary current, the Agulhas Current (0.21 PW). The projected weakening of the Agulhas Current is to compensate for the reduction of the ITF transport, with additional contribution from the spin‐down of the SIO subtropical gyre. Thus, being amplified by the ocean circulation changes in the SIO, the projected Indian Ocean warming trend will be faster than the direct air‐sea heat flux input.

Figure. Cumulative heat budget of the Indian Ocean (zonally and vertically integrated): heat storage change (solid black line), net surface heat flux (blue line), meridional temperature transport (red line), ITF heat transport (green line), and their sum (black dashed line; net surface heat flux + meridional temperature transport + ITF heat transport), as a function of latitude during (a) 1981-2012 from the historical run, (b) 2070–2101 from the RCP8.5 run, and (c) changes between the two (RCP8.5-historical run) over the Indian Ocean basin north of S (see Supporting Text S2 for detailed description of the terms in the supporting information). All the terms in (a) and (b) are integrated from the northern boundary of the Indian Ocean to the south. Positive values mean a warming effect (Units: PW). The error bars represent one standard error based on a Student’s t test (Ma et al., 2020).

Ma, J., Feng, M., Lan, J., & Hu, D. (2020). Projected future changes of meridional heat transport and heat balance of the Indian Ocean. Geophysical Research Letters, 47, e2019GL086803. https://doi.org/10.1029/2019GL086803.