2012: Unprecedented melting in Greenland

[pscot]

Figure 1. Over the course of several years, turbulent water overflow from a large melt lake carved this 60-foot-deep (18.3 meter-deep) canyon in Greenland's Ice Sheet (note people near left edge for scale). Image credit: Ian Joughin, University of Washington.

Watching the weather events of 2012 over Greenland made all seasoned climate watchers a little queasy. The vast ice sheet on the island holds enough water to raise global sea levels by 7.36 meters (24.15 feet) were it all to melt, and the ice melt season of 2012 gave notice that an epic melting of the Greenland Ice Sheet may be underway. According to NOAA's 2012 Arctic Report Card, the duration of melting at the surface of the ice sheet in summer 2012 was the longest since satellite observations began in 1979, and the total amount of summer melting was nearly double the previous record, set in 2010 (satellite records of melting go back to 1979.) A rare, near-ice sheet-wide surface melt event melted 97% of the surface of Greenland's ice sheet on July 11 - 12. While a similar melt event at the summit occurred 1889, but the 1889 event has no basis in the instrumental record from coastal Greenland. It's instead likely that 2012 was Greenland's warmest summer in at least 863 years, since the medieval warm period (see http://www.meltfactor.org/blog/?p=677 and http://www.meltfactor.org/blog/?p=725). It would not be a surprise if this sort of summer began occurring regularly, since the ice sheet reached its darkest value on record in 2012. The darkened surface was due to below average summer snow, soot particles from pollution and forest fires, and record melting. A darker ice sheet absorbs more solar energy, in a vicious cycle that raises temperatures, melts more ice, and further darkens the ice sheet. The amount of melting that was caused by soot from forest fires is important to know, since global warming is likely to increase the amount of forest fires in coming decades. However, the amount of forest fire soot landing on the Greenland Ice Sheet is almost completely unknown, which is why Dr. Box is determined to find out, via the Dark Snow Project.




Figure 2. Smoke from a fire in Labrador, Canada wafts over the Greenland ice sheet on June 17, 2012, as seen in this cross-section view of aerosol particles taken by NASA's CALIPSO satellite. Image credit: Dr. Jason Box, Ohio State University.

Greenland causing 25% of global sea level rise
In a landmark study published in November 2012 in Science,, 47 researchers from 26 laboratories reported that the amount of ice being lost from Greenland and Antarctica has tripled since the 1990s, with Greenland contributing more than twice as much to global sea level rise than Antarctica. The study, "A Reconciled Estimate of Ice-Sheet Mass Balance", found that the two ice sheets were responsible for 20% of the global sea level rise of 3.1 mm/year during the 20-year period 1992 - 2011. The remainder of the rise was due to expansion of the water due to heating of the oceans, melting of mountain glaciers, and unsustainable pumping of ground water. Said co-author Erik Ivins of NASA's Jet Propulsion Laboratory, "The pace of ice loss from Greenland is extraordinary, with nearly a five-fold increase since the mid-1990s." As of 2011, Greenland's contribution to global sea level rise on its own had risen to 20 - 25%, according to an international research group led by the GFZ German Research Centre for Geosciences, in an article published in Earth and Planetary Science Letters on 1 June 2012. If the current exponential ice loss trends continue for the next ten years, Greenland's contribution to sea level rise will double to 1.4 mm/yr by 2022, the researchers said. Many sea level rise researchers expect global sea level to rise by about 1 meter (3.3 feet) by 2100. During the 20th century, global sea level rise was about 0.18 meters (7 inches.)


Figure 3. Monthly smoothed (purple) and unsmoothed (blue) values of the total mass lost from the Greenland Ice Sheet (in Gigatons, Gt) from measurements by the GRACE satellites between March 2002-September 2012. An approximate equivalent global sea level rise figure is on the right axis. Note that the decline in ice mass lost from Greenland is not a straight line--it is exponential, meaning that more ice loss is lost each year than in the previous year. Image credit: 2012 Arctic Report Card.
http://www.wunderground.com/blog/JeffMasters/show.html

[chervilant]

1. I expect very few will understand exponential ...

I try to help my students understand that we're living in exponential times, but it's a difficult concept for most. (Add to this the concept of positive feedback loops, and watch all the glassy-eyed stares you'll get...)

[stuntcat]

2. understanding it is horrifying

There's a quote- Albert Bartlett, "The greatest shortcoming of the human race is our inability to understand the exponential function."
We're a plague right before it's only host dies.

[CRH]

3. Here you go, try this its eye opening, ...

Albert Bartlett on the exponential function

[joshcryer]

7. A must watch for all E&E'rs.

[Green Tea]

4. Please Explain

I am not a global warming skeptic by any means, but I wish someone would the following. If Greenland contains enough water in the form of ice to raise the world shorelines by 23' and all the ice melted last year in four days, why weren't shorelines flooded?

[NickB79]

5. All of the ice did not melt last year

What the scientists have been saying is that all of Greenland's glacial ice was experiencing surface melt.

Basically, the top later of every single glacier and ice sheet on the continent had a layer of liquid water on top of it. Think of it like an ice cube on your kitchen counter: the entire cube can be wet and melting on every side, but not melted away yet.

[TeamPooka]

8. and yet your question is very skeptical. nt