The ice-covered continent of Antarctic is not free from climate change. On the contrary, rise in temperatures at high latitudes is much stronger than that in 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) of the Chinese Academy of Sciences (CAS) and their collaborators investigated the ocean-ice-atmosphere interaction mechanism of the region.
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. They discovered the overall delay in melting season of Antarctic ice sheet in the past 40 years from 1978 to 2020.
They found that 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 regions experience delays in onset, and 65% experience delays in termination. The accumulated delays in both melt onset and end dates over the 40-year observational period amount to 10-15% of the whole summer melt period.
Moreover, the research team clarified delay mechanisms of melting season of Antarctic ice sheet surface: in late spring and early summer of Antarctica, affected by the movement of westerly jet to the poles, surface temperature near the poles dropped, making start time of Antarctic ice sheet melting delayed. At the end of the Antarctic summer, due to the shrinking sea ice extent, heat released from the ocean to the atmosphere increased, resulting in a delay in the end of ice sheet surface melting.
They evaluated how delayed melting season of Antarctic ice sheet surface impacted changes in surface net solar radiation and found that melting season delay in snowmelt region could change 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 increase of sea ice, the delay of melting season has more influence on the total change of radiation balance.
This study suggests 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.
