Antarctic skin temperature warming related to enhanced downward longwave radiation associated with increased atmospheric advection of moisture and temperature

Abstract

We investigate linear trends in Antarctic skin temperatures (temperatures from about the top millimeter of the surface) over the four seasons using ERA5 ensemble mean reanalysis data. During 1950–2020, statistically significant warming occurred over East and West Antarctica in spring, autumn and winter, and over the Antarctic Peninsula in autumn and winter. A surface energy budget analysis revealed that increases in downward longwave radiation related to increases in air temperature and total column integrated cloud had a key role in Antarctic surface warming. There were negative sea level pressure trends around the periphery of Antarctica throughout the year, and the associated circulation contributed to warm advection from the middle latitudes to West Antarctica and the Antarctic Peninsula. Over the interior of East Antarctica, increase in moisture advection from lower latitudes enhanced the low-level cloud cover. A two-dimensional parameter diagram showed that skin temperature trends for time segments longer than 30 years starting before 1960 exhibited statistically significant warming in autumn and winter in East and West Antarctica and the Antarctic Peninsula. In spring, West Antarctica also showed statistically significant warming for long segments. In summer, the Antarctic Peninsula had statistically significant warming trends for long segments and cooling trends for segments less than 30 years. For all the studied time intervals, when skin temperatures had statistically significant positive trends, increases in downward longwave radiation contributed more than 70% of the warming and vice versa. This result demonstrates that on all time and space scales, changes in downward longwave radiation associated with variations in air temperature and atmospheric moisture loading play a dominant role controlling skin temperatures.

Keywords

• Antarctica
• skin temperature
• long-term temperature trend
• longwave radiation
• ERA5