Atmospheric Warming Slowdown during 1998–2013 Associated with Increasing Ocean Heat Content

Although atmospheric greenhouse gas concentrations continuously increased, there was relatively little change in global-averaged surface temperatures from 1998 to 2013, which is known as atmospheric warming slowdown. For further understanding the mechanism involved, we explored the energy redistribution between the atmosphere and ocean in different latitudes and depths by using data analysis as well as simulations of a coupled atmosphere-ocean box model. The results revealed that, compared with observational changes of ocean heat content (OHC) associated with rapid warming, the OHC changes related to warming slowdown are relatively larger in multiple ocean basins, particularly in the deeper layer of the Atlantic. The coupled box model also showed that there is a larger increasing trend of OHC under the warming slowdown scenario than the rapid warming scenario. Particularly, during the warming slowdown period, the heat storage in the deeper ocean increases faster than the ocean heat uptake in the surface ocean. The simulations indicated that the warming patterns under the two scenarios are accompanied by distinct outgoing longwave radiation and atmospheric meridional heat transport, as well as other related processes, thus leading to different characteristics of ocean heat uptake. Due to the global energy balance, we suggest this slowdown has a tight relationship with the accelerated heat transport into the global ocean.