Increasing role of the North Atlantic in anthropogenic ocean heat uptake

Anthropogenic aerosols preferentially cool the Northern Hemisphere, and the effect on surface heat flux into the North Atlantic opposes the greenhouse gas (GHG) effect. However, aerosols are projected to decline in the near future, reinforcing the greenhouse effect on the North Atlantic heat uptake. As a result, the surface uptake of anthropogenic heat by the North Atlantic will increase in the future. At the same time, the projected decline of the  Atlantic meridional overturning circulation (AMOC) and associated meridional ocean heat transport will slowdown the warming of the North Atlantic Ocean, which will in turn keep the surface ocean relatively cold and thus further increase the surface uptake of anthropogenic heat. An article appeared in the Journal of Climate (Shi et al., 2018) reported that under a high-emissions scenario, the surface heat uptake in the North Atlantic Ocean (north of about 30° N) increases from 6% to 26% of the global total.

Figure 6 from Shi et al. (2018): The Qnet trend (W m−2 decade−1) of the ensemble mean of 9 CMIP5 models in (a) RCP4.5 (2006–50) and (b) RCP8.5 (2006–50). Positive indicates excess heat absorbed by the ocean. Stippling indicates regions exceeding 95% statistical significance computed from the two-tailed t test.

Shi, J. R., Xie, S. P., & Talley, L. D. (2018). Evolving relative importance of the Southern Ocean and North Atlantic in anthropogenic ocean heat uptake. Journal of Climate31(18), 7459-7479.

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