How a delayed Antarctic melt season reduces albedo feedback

How a delayed Antarctic melt season reduces albedo feedback
by Staff Writers
Beijing, China (SPX) Jul 28, 2023
The ice-covered continent of Antarctic is not free from climate change. On the contrary, the rise in temperatures at high latitudes is much stronger than the rise in the global mean temperature, a phenomenon known as polar amplification effect.

A research team led by Prof. Guo Huadong from the International Center of Big Data for Sustainable Development Goals (CBAS) and the Aerospace Information Research Institute (AIR), Chinese Academy of Sciences (CAS), in partnership with renowned experts in the field of glacier and climate change investigated into the ocean-ice-atmosphere interaction mechanism of the region, with advances published in the National Science Review.

The team developed an ice sheet surface snowmelt detection method based on machine learning and passive microwave remote sensing data as well as temperature observation data from automatic weather stations, and discovered the overall delay of the melting season of the Antarctic ice sheet in the past 40 years from 1978 to 2020.

This study found that the Antarctic summer is not only "coming late" but also "ending late". Specifically, most Antarctic snowmelt regions have experienced delays in the onset and end of melt, wherein 67% of the snowmelt areas experience delays in onset, and 65% delays in the termination dates. The accumulated delays in both the melt onset and end dates over the 40-year observational period amount to 10-15% of the whole summer melt period.

Through Granger-causality analysis, the research team clarified the delay mechanism of the melting season on the surface of the Antarctic ice sheet: in the late spring and early summer of Antarctica, affected by the movement of the westerly jet to the poles, the surface temperature near the poles dropped, making the melting of the Antarctic ice sheet start time delayed. At the end of the Antarctic summer, due to the shrinking sea ice extent, the heat released from the ocean to the atmosphere increased, resulting in a delay in the end of the melting of the ice sheet surface.

The team evaluated the impact of the delayed melting season on the surface of the Antarctic ice sheet on the change in surface net solar radiation and found that the delay in the melting season in the snowmelt area can change the annual surface net solar radiation by -5+/-3+ 1018 J/year (or -0.26+/- 0.14 W/m2). Compared with the change of surface net solar radiation (-0.19+/-0.31 W/m2 per year) caused by the increase of sea ice, the delay of the melting season in the snowmelt region has more influence on the total change of the radiation balance.

This study points out that incorporating ice sheet surface melting processes into climate and ice sheet models will help improve predictions of regional climate change, ice sheet mass balance, and sea level rise.