The early melt onset (left), red shows areas where melting is occurring. Centre: the dry winter over most of Greenland compared to normal is shown in red, the blue area shows places where more snow than usual has fallen since 1st September 2018. Warmer than usual air over Greenland, Baffin Bay and the central Arctic is visible in red (right), the North Atlantic Oscillation is shown in the graph underneath.



“This winter a persistently positive north Atlantic Oscillation – the weather pattern that also largely controls how cold and wet northern European winters are has led to a generally dry and cold winter in Greenland” said climate scientist Martin Stendel. “IN many ways Europe and Greenland have opposite weather patterns, a mild wet winter in europe often means a relatively cold and dry winter in Greenland”.



The persistent dry winter followed by a mild April has consequences for Greenland glaciers.



“Through most of the winter, the majority of the ice sheet has been unusually dry, which sets it up for enhanced melting - if the right weather conditions occur – in the summer this year” said scientist Ruth Mottram. “A period of warm sunny weather will soon melt this winter’s thin snow cover exposing the darker glacier ice underneath. If this happens we would then expect much faster melting as the dark glacier ice absorbs more energy from the sun than snow. But it all depends on the weather”.



There is an exception though, south east Greenland, where most of the snow in Greenland falls has had an exceptionally wet spring with a lot of snow and rain associated with storms tracking through the north Atlantic. “Actually, there have been several records broken in Greenland for extreme weather in April. Tasiilaq in south east Greenland had its wettest April on record. Aputiteeq, Tasiilaq, Ikermiuarsuk and Summit had their warmest April on record and the Summit station on the top of the ice sheet measured the warmest temperature ever in April, -1,2C on April 30, which is incredibly warm for more than 3000m in altitude. The old record was -6.5C, though this record only goes back about 20 years.” said DMI climatologist John Cappelen.



The warm air mass moving over the Greenland ice sheet has been key to the extensive melting observed this week but substantial melting started already in early April and on the 15th April, field scientists from the PROMICE project observed unusual amounts of melting at quite high elevations in southern Greenland.

https://twitter.com/climate_ice/status/1117809484737536000



Most of this early melting will first refreeze in the underlying snowpack, as shown in the beautiful blue colours visible from satellite (see below) in areas where melting has already got under way. Only later in the season, when the snowpack has disappeared will the melt start running off to the ocean in large quantities, the period known as the ablation season to ice sheet scientists. Overall, the date of onset of the melt season in Greenland does not appear to be strongly connected with the amount of ice that melts over a full season and much will depend on weather over the summer season as to whether or not this will be another record-breaking ice loss season like 2012 or a more muted affair like 2016.