LB 9-82 - “Little summer” drives big melt in the McMurdo Dry Valleys of Antarctica

Background/Question/Methods:

The polar regions experienced record heat waves in March 2022. In the Arctic, March temperatures reached 30 °C above average and sea ice extent was the lowest on record for this typically cold month. In the Antarctic, record temperatures were observed at multiple research stations in continental East Antarctica in late March 2022. Notably, Vostok Station, literally the coldest place on Earth, recorded a new high temperature of -17 °C, more than 40 °C above average conditions for this time of year. Unlike Vostok and other stations on the polar plateau, the McMurdo Dry Valleys are located in a coastal ice-free mountain and valley landscape consisting of alpine glaciers, arid soils, streams, and perennial ice-covered lakes, and are also the focus of an NSF-supported Term Ecological Research (LTER) project that has collected meteorological, hydrological, and ecological data for nearly 30 years. The McMurdo Dry Valleys are uniquely poised to examine the hydrological and ecological impacts of this extreme weather event. Here we describe the extreme weather event from data obtained by automated weather stations and satellite imagery and extrapolate the potential influences of this hot fall on the biotic communities of this extreme ecosystem.

Results/Conclusions:

A record high temperature was observed in the McMurdo Dry Valleys on March 18, 2022, of +6.74 °C at the Lake Vanda automated weather station. This temperature exceeded the previous March record of +1.8 °C in 1996, and the average March temperatures by > 20 °C. High temperatures, winds, and lake-ice ablation were recorded by other automated stations in this region. Additionally, satellite imagery shows significant darkening of soil and sediment surfaces consistent with wetting within 2 days of this event. Soils and sediments in the vicinity of Canada Stream may have experienced wetting up to 20% volumetric water content.

The ecological significance of this extreme weather event is difficult to quantify because the field season in this region ends in February. However, the resident microbial mats and soil biota are capable of rapid activation following wet-up. Wetting of the surface soil as indicated by the satellite imagery suggests a large proportion of the soil community re-emerged from anhydrobiosis in areas where liquid water content exceeded 5%. This weather anomaly may be a harbinger of future climate states where warmer temperatures, higher melt, and thaw are characteristics of a new climate regime in this region of Antarctica.