Wednesday, February 20, 2013

Greenland Melting detected during Winter a climate change concern

Satellite data for the first several weeks of 2013 is showing that melting is occurring in south east Greenland. In summer this would be expected, but January-February is the dead of winter. Some portions of Greenland have experienced more than 30 days of melting since the start of this year, a worrying trend.

According to email correspondence with Ted Scambos from National Snow and Ice Data Centre (NSIDC) sent to Tom Yulsman, all of Greenland has been 2 to 6 degrees C warmer than the 30 year mean. Tom quotes Ted Scambos on his blog: "Air temperatures along the southeastern coast for the period Feb 10 – 15 are running 2 to 6 C above normal. Nuuk, the capital, on the very southern west coast, is currently just a couple of degrees below freezing."

Related: Is Climate Change causing an exponential rate of Ice sheet Mass Loss, sea level rise? | Global Warming threshold for Greenland Ice Sheet collapse reduced to 1.6 degrees C


Now the incidence of melting may actually be fairly small, but the fact it is occurring and being detected is symptomatic of the rate of global warming in Greenland. Warming is occurring at twice the global average. Again a quote from Yulsman's blog - Ted Scambos said: "The main message is that a short period of melting during the day will trip our melt detection algorithm and count as a day. Overall, this is a bit unusual — a warm spell — but I would downplay its exceptional nature at this point."

This winter melting has been detected in the south east, but according to researchers parts of west Greenland have warmed more than 10°C in winter in the last 20 years.

"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."



The recent warming has also been compared to earlier less pronounced episodes during the early twentieth century. The paper by Edward Hanna and other researchers - Recent warming in Greenland in a long-term instrumental (1881–2012) climatic context: I. Evaluation of surface air temperature records - says: "We demonstrate very strong recent warming along the west coast of Greenland, especially during winter (locally >10?°C since 1991), and rather weaker warming on the east Greenland coast, which is influenced by different oceanographic/sea-ice and meteorological synoptic forcing conditions to the rest of Greenland."

Edward Hanna said "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."

While Greenland is warming faster than average, an even greater winter temperature anomaly is occurring at Svalbard with temperatures 10-12 degrees C above normal since December, according to Scambos. "A very strong winter warming is identified for the latest decades," for Svalbard according to a Eirik J Forland et al (2011), with projected warming rates three times stronger than observed in the last 100 years.

Greenland Summer melting set a new record in 2012 with surface melting recorded over 97% of the ice sheet surface. Detection of winter surface melting may be symptomatic and presage another record melt year for Greenland in 2013.

It is estimated that the Greenland Ice sheet lost 263±30 billion tons of ice per year from 2005 to 2010. Another 81 billion tons per year was lost from Antarctica. While the East Antarctic ice sheet has marginally increased in mass from extra precipitation, the small gain has been more than offset by losses from the Antarctic Peninsula and West Antarctic Ice sheet (WAIS). So far ice sheet mass loss has contributed about 0.6 millimetres per year to the 3 millimetre average global rise of sea levels.

Sources:
  • Tom Yulsman, 18 February 2013 - Snow in Greenland is melting — in winter
  • Liz Kalaugher, 7 January 2013 - West Greenland warming hits 10°C
  • Edward Hanna et al (2012), Environ. Res. Lett. 7 045404
    doi:10.1088/1748-9326/7/4/045404 Recent warming in Greenland in a long-term instrumental (1881–2012) climatic context: I. Evaluation of surface air temperature records (Full Paper)
  • Eirik J. Førland, Rasmus Benestad, Inger Hanssen-Bauer, Jan Erik Haugen, and Torill Engen Skaugen, Temperature and Precipitation Development at Svalbard 1900–2100 (Full paper), Advances in Meteorology, vol. 2011, Article ID 893790, 14 pages, 2011. doi:10.1155/2011/893790
  • Images from the NSIDC 19 February Greenland Ice Sheet Today website