These increasingly frequent events are altering the traditional dynamics of melting and profoundly changing the state of snow and ice, the most vulnerable elements of the polar climate system. 

Snow accumulation during winter no longer compensates for summer losses: for decades, the annual balance has been clearly negative. Extreme melting episodes — which can last for days or weeks — cause much higher than usual melting rates. These are genuine heatwaves, but they are not defined by air temperature, but rather by the melting that causes ice and snow to disappear. 

This article was originally published in The Conversation.