Delayed Antarctic melt season reduces albedo feedback

Antarctica's response to climate change varies greatly both spatially and temporally. Surface melting impacts mass balance and also lowers surface albedo. We use a 43-year record (from 1978 to 2020) of Antarctic snow melt seasons from space-borne microwave radiometers with a machine-learning algorithm to show that both the onset and the end of the melt season are being delayed. Granger-causality analysis shows that melt end is delayed due to increased heat flux from the ocean to the atmosphere at minimum sea-ice extent from warming oceans. Melt onset is Granger-caused primarily by the turbulent heat flux from ocean to atmosphere that is in turn driven by sea-ice variability. Delayed snowmelt season leads to a net decrease in the absorption of solar irradiance, as a delayed summer means that higher albedo occurs after the period of maximum solar radiation, which changes Antarctica's radiation balance more than sea-ice cover. The Antarctic snowmelt season shows a delay over the satellite record. Decreasing spring and early summer surface temperature leads to delay of snowmelt onset, while the melt season ends later mainly due to enhanced ocean-atmosphere heat exchange. The delay in snowmelt season results in reduction of net surface solar radiation.

Automated summary

Antarctica's response to climate change varies greatly in location and time. Using a 43-year record, we found that both the start and end of the snowmelt season in Antarctica are being delayed. The delay in the melt season is caused by increased heat flux from the ocean to the atmosphere and is influenced by sea-ice variability. This delay in snowmelt season results in a decrease in surface solar radiation absorption.