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- Title
Surface Albedo Feedback, Seasonal Heat Storage and Meridional Heat Transport Determine the Seasonality of Recent Warming in Antarctica.
- Authors
Dai, Haijin
- Abstract
The reanalysis data suggest that recent surface warming over Antarctica start in 2016. In this study, using reanalysis data and numerical simulations, I attempt to determine the important mechanisms accounting for seasonal surface warming in Antarctica. The results suggested that seasonal surface warming in Antarctica is mainly determined by the surface energy budget over the Antarctic via horizontal heat advection. The surface energy budget anomaly over the Antarctic, which is mainly determined by anomalous solar radiation absorption, anomalous ocean heat content, and anomalous meridional atmospheric heat transport (AHT), is triggered by Antarctic sea‐ice loss and thus determines the observational seasonality of recent warming in Antarctica via surface horizontal heat advection. In austral summer (December–January–February), additional solar radiation absorption induced by sea‐ice loss and additional AHT from lower latitudes increase the energy budget over the Antarctic. Surface warming, more longwave radiation, and additional energy stored in the upper (deeper) ocean for short (long) time periods explain the additional energy sinks. During austral autumn‐winter (March–August), additional seasonal heat storage (SHS; mainly stored in the upper ocean) is released to the atmosphere and warms the surface. Although the AHT anomaly contributes similarly to the solar radiation absorption/SHS anomaly during April–August, the poleward AHT largely decreased in June due to the weaker eddy activity induced by strong warming at Southern Hemisphere midlatitudes, which counteracts the additional SHS release and cools the Antarctic(a). Plain Language Summary: The Antarctic is the polar region in the Southern Hemisphere, which includes both continent (Antarctica) and ocean (Southern Ocean). In contrast to Arctic warming, which is mainly determined by local forcing and feedback; recent SH polar (Antarctic) warming has been determined by local radiation and ocean heat content anomalies, as well as by meridional heat transport anomalies. With reanalysis data and numerical simulations, we obtained the following conclusions. (a) The seasonality of recent surface warming in Antarctica is mainly induced by additional energy over the Southern Ocean, since additional energy over the Southern Ocean can be transported to Antarctica via anomalous winds. (b) Additional solar radiation reaches the sea surface due to sea‐ice loss, which is stored (released) in (from) the upper ocean and causes weaker (stronger) surface warming in the warm (cold) season. (c) In recent years, Antarctic warming has increased the meridional temperature gradient and strengthened eddy activity, which has led to an increase in meridional heat transport and Antarctic warming. However, there is an exception in June. Strong warming at Southern Hemisphere midlatitudes decreases the meridional temperature gradient and weakens eddy activity, which leads to a decrease in meridional heat transport and results in Antarctic cooling. Key Points: Local radiative feedback and remote forcing warm the polar region of Southern Hemisphere, although additional energy is stored in the oceanSeasonal warming in Antarctica is mainly determined by anomalies in solar radiation, seasonal heat storage and meridional heat transportStronger (weaker) eddy activity increases (decreases) poleward meridional heat transport and warms (cools) Antarctica in most months (June)
- Subjects
ANTARCTICA; ALBEDO; HEAT storage; SEA ice; ENERGY budget (Geophysics); RADIATION absorption; SOLAR radiation; ENTHALPY
- Publication
Journal of Geophysical Research. Atmospheres, 2024, Vol 129, Issue 5, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD040000