Ocean warming acceleration in Atlantic tied to the changes in ocean heat transport

Change in ocean warming rate is essential for evaluating the current climate change and predict future climate conditions. It has been confirmed that in the context of accelerated warming of the Earth climate system, the global oceans have been warming, especially since the 21st century, with a certain rate of acceleration. Because the local ocean heat content (OHC) changes are mainly balanced by the net sea surface heat flux (F_S) and the oceanic heat divergence/convergence (OHD), the acceleration of ocean warming is closely related to the trend of the latter two. In this study, we first calculate the oceanic meridional heat transport (MHT) as a residual of energy budget including OHC, F_S, and heat related to sea ice volume changes (Q_ice), and then adjust the discrepancy caused by systematic errors in different data and mismatch between them on a monthly basis. Our estimated MHT is compared to the results from RAPID observations, which shows good agreement between the two, with a correlation coefficient of 0.73 in the time series during January 2009 - December 2020. Based on the multiple datasets, we further evaluate the accelerated/decelerated changes in Atlantic OHC associated with the ocean and air-sea energy flow changes. The results show that during 1985-2016, in the north Atlantic Ocean, the ocean warming is slowing down, which are mainly dominated by the decreased OHD, while the southern Atlantic Ocean is accelerating warming mainly caused by the strengthened OHD. Therefore, MHT changes accompanied by the energy flow within the ocean play a more important role to the regional ocean warming acceleration than the changes in regional sea air heat exchange. The methodology we use here provides a method to estimate the heat transports, and can be used to analysis the ocean warming rates and Earth’s energy changes, and to detect the future climate variability.