Abstract
We document the occurrence in December 2015 of unprecedented high monthly mean temperatures in the observational record of mountain sites in the eastern Alps. For the first time in the last 150 years mean December temperature exceeded 0 °C at elevations between 2100 and 2500 m, with December mean anomalies exceeding 6.5 °C with respect to the 1971–2000 mean. Along with the absence of snow cover, such temperatures might have lead to unprecedented winter ablation of glaciers in this elevation range. Smaller temperature anomalies occurred in surrounding low elevation sites, highlighting the key role of topography in this event. Specifically, strong inversions associated with the very stable synoptic conditions during the month amplified the anomalies at the high elevations of the mountain glacier sites. We analyze the processes underlying this exceptional event and place this anomaly within the context of future warming scenarios over the region.
Highlights
Recent decades have been characterized by the occurrence of heat waves and warm periods of exceptional magnitude, such as the summer of 2003 in Europe[1], the 2010 heat wave in Russia[2], or the summer of 2013 in Australia[3]
This issue is relevant for mountain environments, since different studies have shown that topography can locally amplify the surface warming[10,11,12]
Mountain glaciers are considered to be sensitive indicators of climate variability[16]. They react in a relatively simple way to changes in climate, as their mass balance mainly depends on variables such as air temperature, precipitation, humidity and wind speed[16, 17]
Summary
Recent decades have been characterized by the occurrence of heat waves and warm periods of exceptional magnitude, such as the summer of 2003 in Europe[1], the 2010 heat wave in Russia[2], or the summer of 2013 in Australia[3].
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