Five consecutive years of mass balance observations to understand glacier reaction to present climate change (Austre Lovénbreen, Svalbard 79°N)

Résumé En

Since 2008, mass balance is measured on the Austre Lovénbreen (Spitsbergen, Norway, 79 N) as part of the Hydro-Sensor-FlOWS program. The observations are made at a very fine scale: on the 4.5 km 2 glacier, mass balance is measured each September with 36 stakes. Snow cover is measured at the end of April. 20 air-temperature loggers give hourly data on the thermal state of the glacier. In addition automatic cameras provide 3 pictures per day. These pictures are used to determine whether ice is visible or snow covered all over the glacier. Climate parameters provided by the nearby Ny-Alesund weather station are also used. The influence of climatic parameters on mass balance has been explored. Over the last five years, Austre Lovénbreen's mean mass balance is -17 cm. Four of the five years are between -9 and -26 cm. One year (2010-2011) clearly stands out with a value of -123 cm corresponding to a very important ablation on the entire glacier. There is no clear correlation between mass balance values and yearly cli- matic parameters. Seasonal variations seem to explain more. High temperatures and consequent liquid precipitation are partially explaining mass balance results. A "warm" winter with important precipitation (like in January 2012) will give rain at sea level but huge amounts of snow on the glacier at higher altitude (100-550 masl). A hot summer will result in important ablation, even more so if it is rainy too. The five-year survey also shows the importance of short-term warm and rainy events. Strong events can account for an important part of a year's mass balance. Considering the longest mass balance series of the neighbouring glacier (Midtre Lovénbreen), we will also discuss the relationship between mass balance and the North Atlantic Oscillation or the Arctic Oscillation.