The Impacts of Changes in Cloud Radiative Effects on Poleward Atmospheric and Oceanic Energy Transport in a Warmer Climate

Abstract:

The changes in cloud radiative effect (CRE) under global warming, or the cloud feedback, are suggested to modulate the responses of meridional energy transport and largely contributes to the uncertainty in anomalous energy transport by previous studies that theoretically estimate the contributions of different feedback processes to the anomalous energy transport via meridionally integrating individual radiative feedbacks. Here, we apply a cloud-locking technique to further investigate the radiative and dynamical adjustments induced by the CRE changes in a fully-coupled climate model, CESM. Under global warming, most of the increase of southward energy transport in the Southern Hemisphere can be attributed to changes in CRE. In contrast, 87% of the changes in CRE are balanced by increasing outgoing longwave radiation in the Northern Hemisphere, revealing an overestimation of CRE’s influence on energy transport using the theoretical integration approach. The increase in poleward transport in the Southern Hemisphere is mostly accomplished by an anomalous wind-driven overturning circulation in the ocean around 30^oS and by enhanced eddy-induced anomalous atmospheric heat transport related to the increased moist static energy gradient in high latitudes. The analyses also suggest an important role of ocean heat uptake in modulating the responses of temperature and energy transport to CRE changes.