Increased cloud cover acts as a blanket, keeping heat in, less clouds allows cooling and more ice.

BEIJING, April 26 (Xinhua) — Researchers have discovered that lower cloud coverage in the Antarctic can promote sea ice growth.

Unlike the rapid decline of Arctic sea ice in the warming climate, Antarctic sea ice witnessed a modest extension over the past four decades, according to the paper published in the Journal of Geophysical Research-Atmospheres.

The researchers from China and the United States found that Antarctic sea ice had a strong rebound from 2011 to 2012.

“We quantified the effects on sea ice growth via a thermodynamic model based on reanalysis and satellite data and concluded that lower cloud coverage cooled the sea surface and accelerated the sea ice storage,” said Wang Yunhe, a researcher from the Institute of Oceanology, Chinese Academy of Sciences.

“Clouds are like a down jacket for the Antarctic to preserve heat during winter,” said Bi Haibo, a researcher from the institute. “Fewer clouds mean more heat is lost from the ocean.”

Rapid temperature decline and thicker sea ice in the Antarctic during the winter in 2011 was mainly due to fewer clouds, he said.

The paper:
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JD029435

The Contributions of Winter Cloud Anomalies in 2011 to the Summer Sea‐Ice Rebound in 2012 in the Antarctic

Abstract

Unlike the rapid decline of Arctic sea ice in the warming climate, Antarctic sea‐ice extent exhibits a modest positive trend in the period of near four decades. In recent years, the fluctuation in Antarctic sea ice has been strengthened, including a decrease toward the lowest sea‐ice extent in February 2011 for the period of 1978–2016 and a strong rebound in the summer of 2012. The sea‐ice recovery mainly occurs in the Weddell Sea, Bellingshausen Sea, Amundsen Sea, southern Ross Sea, and the eastern Somov Sea. This study offers a new mechanism for this summertime sea‐ice rebound. We demonstrate that cloud‐fraction anomalies in winter 2011 contributed to the positive Antarctic sea‐ice anomaly in summer 2012. The results show that the negative cloud‐fraction anomalies in winter 2011 related to the large‐scale atmospheric circulation resulted in a substantial negative surface‐radiation budget, which cooled the surface and promoted more sea‐ice growth. The sea‐ice growth anomalies due to the negative cloud forcing propagated by sea‐ice motion vectors from September 2011 to January 2012. The distribution of the sea‐ice anomalies corresponded well with the sea‐ice concentration anomalies in February 2012 in the Weddell Sea and eastern Somov Sea. Thus, negative cloud‐fraction anomalies in winter can play a vital role in the following summer sea‐ice distribution.