Extreme temperature events for the past 19 years in the McMurdo Dry Valleys, Antarctica linked to mesoscale meteorological variability

Abstract

The McMurdo Dry Valleys (MDVs) in Antarctica have a unique environment classified as a hyper-arid desert with glacier runoff being the main source of liquid water. Previous studies have identified winds as the controlling factor of the climate in this region and especially the occurrence of foehn induced warming. Episodic foehn warming during the austral summer can contribute to above freezing temperatures sustained for multiple days. Years with extreme glacial runoff leading to flooding have been correlated with a higher occurrence of foehn induced warming events. Understanding the temporal availability of meltwater caused by extreme meteorological events is highly important since it is a dependant variable to the functioning of the area’s fragile ecosystem. Synoptic scale circulations in the surrounding Ross Sea Region are a driving factor for the occurrence of foehn warming in the MDVs with the local mesoscale meteorology modulating the spatiotemporal variability of the foehn-induced near-surface warming. AntAir ICE, a newly developed daily mean near surface air temperature dataset with a spatial grid resolution of 1 km2 has proven capable of capturing these mesoscale temperature variabilities for multiple seasons within the complex topography of the MDVs. A case study on the 2nd of January 2020 where the maximum temperature measured in a Lake Vanda automatic weather station was above +9 degrees Celsius with multiple valleys experiencing foehn induced warming, displayed a clear warming signal for the MDVs in AntAir ICE. The atmospheric dynamic analysis from the numerical weather prediction model the Antarctic Mesoscale Prediction System (AMPS) indicated a clear foehn signature. This event was linked to a meso-low located in the Ross Sea which was detected in the climate re-analysis ERA5 mean sea level pressure dataset. By confidently identifying these warming events within the MDVs where there is a relatively high availability of Automatic Weather Stations and AMPS predictions, has allowed for further exploration of extreme sustained warming and potentially foehn induced warming along the terrestrial coastal margin of Antarctica. Using AntAir ICE, warming events during the austral summer season from November to February for the period 2003 to 2021 with sustained daily mean temperatures above freezing for multiple days have been identified for the Ross Sea Region. This study aims at capturing the mesoscale meteorological and climatological variability for multiple seasons within the Ross Sea Region, while linking these extreme warming events to larger scale circulation patterns can allow for understanding local extreme events in context of shifting large scale circulation drivers.