"Some locations along the west coast of Greenland have warmed really strongly by about 2–4°C in summer and as much as 10°C locally in winter – in their average surface air temperatures since 1991," Edward Hanna of the University of Sheffield, UK, told environmentalresearchweb. "In general, warming has been much stronger in west Greenland than in the east. Similar warming trends are seen on the western flank of the ice sheet – at 1200 metres above sea level – as on the west coast, which indicates a significant impact of this strong warming on enhancing ice-sheet melt and mass loss."

As west Greenland has been one of the strongest warming regions globally over the last decade, Hanna said that we should not be surprised about the recent findings of record loss of mass from the Greenland ice sheet (Rignot et al. 2011 Geophys. Res. Lett.) or by the NASA announcement of record surface melt of the ice sheet in July 2012.

Along with colleagues from Los Alamos National Laboratory, US, the Danish Meteorological Institute, Swiss Federal Institute WSL, Swiss Federal Institute of Technology and École Polytechnique Fédéral de Lausanne, Switzerland, Hanna used data on daily mean, minimum and maximum surface air temperature from Greenland coastal weather stations and a single site on the Greenland ice sheet. Five sites had records going back to before 1900; many others started collecting measurements in around 1960.

"There has not been a systematic analysis of the main meteorological station surface air-temperature records for a decade, and during that time there have been significant warming and other climate changes affecting Greenland," said Hanna. "We wanted to know how this warming varies by region and season, and also how significant the recent high temperatures are compared with a well known previous warm period around 1940."

The 1930s warming trend was much more modest, wrote the researchers in Environmental Research Letters (ERL) , but was also strongest – at ∼5°C – for west Greenland in winter for 1901–1930 and 1911–1940. From 2001–2012, the Greenland coastal mean surface air temperature in winter was around 1.6°C above its early 20th century peak, and roughly 0.8°C higher in summer.

In addition to climate change, the team ascribed the west Greenland warming to changes in the North Atlantic Oscillation and Greenland blocking index that have caused mild southerly airflows to hit the western flank of the Greenland ice sheet more frequently. The airflows may not always reach east Greenland, which is also often influenced by the cold east Greenland current.

Now the team plans to analyse in detail the reasons for the regional and seasonal variations in temperature changes over Greenland for the last one to a hundred years. "We are studying causal factors such as the North Atlantic Oscillation and Greenland blocking index, which both measure changes in atmospheric circulation and jet-stream activity over Greenland, as well as human-driven global warming," said Hanna. "The extreme warming over west Greenland recently is most likely due to these natural and human climate-forcing factors conspiring together."

Hanna believes the team's analysis of maximum and minimum daily temperatures, in addition to mean daily temperatures, will give a greater insight into the climatic factors behind the warming.