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article imageGreenland Ice Sheet melt 'unprecedented' in 2012

By Robert Myles     Feb 12, 2013 in Environment
After 2012's unprecedented melting of Greenland's Ice Sheet, the National Snow and Ice Data Center (NSIDC) last week launched a new website dedicated to providing up to date satellite data and scientific analysis of what is happening in Greenland.
The new NSIDC pages, are titled “Greenland Ice Sheet Today” and will feature satellite images of ice sheet updated daily showing the melt experienced by the Greenland Ice Sheet as well as scientific analysis.
The Greenland Ice Sheet is an important climate indicator as well has having a significant impact on climate. It contains massive volumes of frozen fresh water with the potential to raise sea levels and cause coastal flooding in many areas if ice sheet melt continues.
Greenland’s Ice Sheet expands in winter and contracts in summer but over the past 34 years or so of satellite and ground observation, the mass of the ice sheet has been reducing. That is to say, the winter ice sheet has gradually become both thinner and less widespread. Whilst the NSIDC records that ice core records reveal similar evidence of past heatwaves, the current annual extent of Greenland Ice Sheet melt has never been seen at such levels since satellite records began.
In 2012, as reported in Digital Journal, the Greenland Ice Sheet experienced the strongest melt season yet seen with some of the most massive icebergs ever recorded calving from Greenland’s glaciers at an unprecedented rate. As NSIDC puts it,
“Greenland’s surface melting in 2012 was intense, far in excess of any earlier year in the satellite record since 1979. In July 2012, a very unusual weather event occurred. For a few days, 97% of the entire ice sheet indicated surface melting.”
So significant was the heightened ice sheet melt in Greenland during 2012, that the NSIDC has now published a special report, “An intense Greenland melt season: 2012 in review.” The key points to emerge from the report are:
• The 2012 melt was the most intensive observed since satellite observation started in 1979. At one point in July 2012, 97% of the Greenland Ice Sheet was experiencing ice melt.
• The 2012 melt season lasted two months longer than the average since 1979.
• 2012 was the first year where ice melt was recorded at some point over the whole ice sheet.
• In July 2012, some inland areas two miles above sea level, experienced ice melt for the first time since observations began. Previously, such events had only been observed on a few occasions in ice core samples dating back 1,000 years.
• Such was the increased and unprecedented ice melt at higher elevations that the intensity of run-off water caused damage to bridges and other structures.
• Zones where ice melts and refreezes, known as ‘facies,’ are steadily moving uphill. In turn this is contributing to a ‘runaway’ melt effect as the underlying, previously unexposed surface warms up causing future melts to become more rapid and frequent.
• Summer warmth in Greenland in 2012 was both more widespread and more intense. In melt areas, June to August temperatures were some 2°C higher than the 1981 to 2010 average. Over the ice sheet as a whole, temperatures were 1.5°C above the average.
The graph above shows the daily extent of melt during 2012 on the Greenland Ice Sheet surface as a p...
The graph above shows the daily extent of melt during 2012 on the Greenland Ice Sheet surface as a percentage, compared to the average from 1981 to 2010.
National Snow & Ice Data Center/University of Georgia
Not only is the ice sheet significant from the observational standpoint of accelerated melt, but the effects of increased melting of the Greenland Ice Sheet can alter weather patterns over great distances. Increasing ice sheet melt means increasing flows of denser fresh water into the northern Atlantic and higher temperatures in the Arctic generally due to a reduction in the amount of the Sun’s rays reflected back into space as a result of reduced ice cover. White ice and snow is highly reflective but darker, bare rocks and earth absorb the Sun’s rays, heating up.
2012 was the warmest year on record for the Greenland Ice Sheet since records began in 1979 and whilst a contributing factor last year was undoubtedly an area of high pressure which persisted for most of the 2012 summer, the NSIDC review of 2012 also highlighted another trend observed by researchers from the University of Sheffield. In a paper "Recent warming in Greenland in a long-term instrumental (1881–2012) climatic context: I. Evaluation of surface air temperature records," Professor Edward Hanna and his colleagues found that warming had been much stronger along western Greenland than in the east since 1991. Focussing on data from 1991 to 2012, they found some locations along Greenland’s west and northwest coast had warmed between 2°C and 4°C during summer. More alarmingly, the Sheffield researchers also discovered that some locations along those same coasts had warmed by as much as 10°C in winter.
More about Greenland Ice Sheet, Arctic, Global warming, Climate change, Ice melt
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