Scientists Put Recent Antarctic Minimum Snowmelt into Context
28.10.2009 - Atmosphere & Space, Water & Oceans, Ice & Snow, Other, Antarctic
A recent study by Drs. Andrew Monaghan and Marco Tedesco published in October 2009 in Geophysical Research Letters documented minimum snowmelt n Antarctica during the 2008-09 austral summer and a lower than normal snowmelt during several recent years. The results, which are based on records from the satellite era going back 30 years, were incorrectly interpreted by numerous blogs, which prompted the two scientists to debunk on RealClimate.org the myths circulating in the blogosphere.
Many blogs jumped to the conclusion that the study meant Anatarctica wasn't warming, when in fact they neglected that the study showed warming in Antarctica has been occurring mostly in winter and spring. The bloggers also oversimplified causality, confusing the scientists' prediction for the future, and neglected that the study showed that the same mechanism that has primarily caused low snowmelt in recent years will likely change so that snowmelt will be enhanced in the coming decades.
Monaghan and Tedesco's study found that low melt rates between 1979 and 2009 have been related to the westerly winds around Antarctica, known as the Southern Hemisphere Annular Mode (SAM). During the past 30-40 years, the SAM has been strengthened due to the man-made hole in the ozone layer, which in turn has weakened the longer-term summer warming over Antarctica.
Thanks to the Montreal Protocol, the ozone layer is expected to recover in the next 15-50 years, which will cause the increasing summer SAM trends to subside. As the cooling impact of the SAM subsides, it will likely cause summer temperature increases over Antarctica to become stronger and more widespread. This was in fact the key conclusion that the pair of researchers had reached in their study. Additionally, their results also agree with studies that have shown cooling or slower warming trends over the past three decades due to increasing SAM trends over the same period of time, and do not contradict findings that have shown strong regional warming in West Antarctica and along the Antarctic Peninsula.
