Subtropical Clouds Key to Southern Ocean Teleconnections to the Tropical Pacific

Abstract
Excessive precipitation over the southeastern tropical Pacific is a major common bias that persists through generations of global climate models. While recent studies suggest an overly warm Southern Ocean as the cause, models disagree on the quantitative importance of this remote mechanism in light of ocean circulation feedback. Here, using a multimodel experiment in which the Southern Ocean is radiatively cooled, we show a teleconnection from the Southern Ocean to the tropical Pacific that is mediated by a shortwave subtropical cloud feedback. Cooling the Southern Ocean preferentially cools the southeastern tropical Pacific, thereby shifting the eastern tropical Pacific rainbelt northward with the reduced precipitation bias. Regional cloud locking experiments confirm that the teleconnection efficiency depends on subtropical stratocumulus cloud feedback. This subtropical cloud feedback is too weak in most climate models, suggesting that teleconnections from the Southern Ocean to the tropical Pacific are stronger than widely thought.

The effect of the Antartic climate change on the changes in the sea surface temperature in the Pacific Ocean has been identified. Since an increase in the average global sea surface temperature (SST) could have profound impacts on climate and weather systems, their findings are expected to be of great help in improving climate forecasts in the mid-latitude, as well as future climate predictability.

A research team, led by Professor Sarah Kang in the Department of Urban and Environmental Engineering at UNIST, has recently demonstrated the Southern Ocean–driven teleconnection mechanism mediated by subtropical low cloud feedback, which is erroneously weak in climate models. This suggests that the impact of the Southern Ocean bias on the tropical precipitation bias is likely to be stronger than recent studies suggest, noted the research team.

Figure. The impact of Southern Ocean cooling on the tropical Pacific. 

Their findings have been published in the August 2022 issue of PNAS. This work has been supported by the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT of South Korea.

Journal Reference
Hanjun Kim, Sarah M. Kang, Jennifer E. Kay, et al., “Subtropical clouds key to Southern Ocean teleconnections to the tropical Pacific,” PNAS, (2022).