Polar Maritime

Like butter: Study explains surprising acceleration of Greenland’s inland ice 16 July 2013 AGU Release No. 13-35 For Immediate Release WASHINGTON, DC — Surface meltwater draining through cracks in an ice sheet can warm the sheet from the inside, softening the ice and letting it flow faster, a new study finds. During the last decade, researchers have captured compelling evidence of accelerating ice flow at terminal regions, or "snouts," of Greenland glaciers as they flow into the ocean along the western coast. Now, the new research shows that the interior regions are also flowing much faster than they were in the winter of 2000-2001, and the study authors propose a reason for the speedup. "Through satellite observations, we determined that an inland region of the Sermeq Avannarleq Glacier, 40 to 60 miles from the coast, is flowing about 1.5 times faster than it was about a decade ago," said Thomas Phillips, lead author of the new paper and a research associate at the time of the study with the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, Boulder. In 2000-2001, the inland segment was flowing at about 40 meters (130 feet) per year; in 2007-2008, that speed was closer to 60 meters (200 feet) per year. "At first, we couldn't explain this rapid interior acceleration," Phillips said. "We knew it wasn't related to what was going on at the glacier's terminus. The speedup had to be due to changes within the ice itself." To shed light on the observed acceleration, Phillips and his team developed a new model to investigate the effects of meltwater on the ice sheet's physical properties. The team found that meltwater warms the ice sheet, which then—like a warm stick of butter—softens, deforms, and flows faster. Previous studies estimated that it would take centuries to millennia for new climates to increase the temperature deep within ice sheets. But when the influence of meltwater is considered, warming can occur within decades and, thus, produce rapid accelerations. The paper has been accepted for publication in theJournal of Geophysical Research: Earth Surface, a journal of the American Geophysical Union. The researchers were tipped off to this mechanism by the massive amount of meltwater they observed on the ice sheet's surface during their summer field campaigns, and they wondered if it was affecting the ice sheet. During the last several decades, atmospheric warming above the Greenland Ice Sheet has caused an expanding area of the surface to melt during the summer, creating pools of water that gush down cracks in the ice. The meltwater eventually funnels to the interior and bed of the ice sheet. As the meltwater drains through the ice, it carries with it heat from the sun. "The sun melts ice into water at the surface, and that water then flows into the ice sheet carrying a tremendous amount of latent energy," said William Colgan, a coauthor and CIRES adjunct research associate. "The latent energy then heats the ice." The new model shows that this speeds up ice flow in two major ways: One, the retained meltwater warms the bed of the ice sheet and preconditions it to accommodate a basal water layer, making it easier for the ice sheet to slide by lubrication. Two, warmer ice is also softer (less viscous), which makes it flow more readily. "Basically, the gravitational force driving the ice sheet flow hasn't changed over time, but with the ice sheet becoming warmer and softer, that same gravitational force now makes the ice flow faster," Colgan said. This transformation from stiff to soft only requires a little bit of extra heat from meltwater. "The model shows that a slight warming of the ice near the ice sheet bed—only a couple of degrees Celsius—is sufficient to explain the widespread acceleration," Colgan said. The findings have important ramifications for ice sheets and glaciers everywhere. "It could imply that ice sheets can discharge ice into the ocean far more rapidly than currently estimated," Phillips said. "It also means that the glaciers are not finished accelerating and may continue to accelerate for a while. As the area experiencing melt expands inland, the acceleration may be observed farther inland." The study's results suggest that to understand future sea-level rise, scientists need to account for a previously overlooked factor—meltwater's latent energy—and its potential role in making glaciers and ice sheets flow faster into the world's oceans. In 2007, the Intergovernmental Panel on Climate Change (IPCC) wrote that one of the most significant challenges in predicting sea-level rise was "limited" understanding of the processes controlling ice flow. The IPCC's next assessment is due out in 2014. "Traditionally, latent energy has been considered a relatively unimportant factor, but most glaciers are now receiving far more meltwater than they used to and are increasing in temperature faster than previously imagined," Colgan said. "The chunk of butter known as the Greenland Ice Sheet may be softening a lot faster than we previously thought possible." http://www.agu.org/news/press/pr_archives/2013/2013-35.shtml

Temps or Rainfall BFTV ? Thanks.

Not long to wait now then, have snow every year here, March produced some of the largest drifts I have seen for years with severe drifting in Easterly gales, some 4/5 meters and up to the bedroom windows in places localy. I see you are at 300m to, it helps being out in open away from built up areas as temps can really plummet, we had a low of -20c during 2010 winter here. Thanks Bish, took them specially for you It looked a lot better than that before they cut for hay last week !

A high of 26.8 here today, And 31.1c in the sun...

Snow patches remaining on and around Braeriach today.http://glencoemountaineer.blogspot.co.uk/2013/07/crystal-ridge.html

Even the models dont have a clue a.t.m, after the stormy spell 2nd half of next week, we could have another reload of hot/warm weather, or it could turn unsettled of the Atlantic... Im more on the thought's of unsettled with high pressure to our N/W, but we shall see. Wait until later next week for a clearer picture from the models.

Well the tarmac is melting on some of the tight hair-pin bends round here, currently 27.7c.. in the shade. Some nice cumulus bubbling up now.

Here you go Bish..Taken 10min ago, comparison now and 4 months ago, Hopefully we will see the same in 4 months ! 27.7c just now.

Yes Bish, will pop them up later, will take a few shots this afternoon for you.

Up to 25,5c here in the shade and 28.8c in the sun, Yes Botty, certainly the longest hottest spell since 2006.

25.5c here in the shade, and 28.7c in the Sun, Some prime places could touch 32/33c later i think. Just got back from a cheeky dip down Lathkill Dale, the water is freezing as its all spring water at the head of the river. Perfect for cooling me off... I now have ball's like isotopes.

23.4c here now and rising..

HOW HIGH ARE NOCTILUCENT CLOUDS? Noctilucent clouds are our planet's highest clouds--but exactly how high are they? The textbook answer is 82-82 km, but textbooks can be wrong. Peter Rosén of Stockholm, Sweden, decided to find out for himself. "On July 4th I photographed some interesting NLCs," he explains. "After uploading them on Spaceweather, I noticed that P-M Hedén had photographed the same formations and at the same time from a location 26 km (16 miles) north of mine. I decided to make precise measurements of the same features in both pictures with respect to the stars and try to determine the exact geographical position and height of these NLCs." Scroll past the images to learn more: "Some years ago I found a very useful calculator put online by Paul Schlyter to measure the position and altitude of Perseid meteors. By entering the geographical position of both observers and the respective coordinates of an object in the sky, it will compute the position and altitude of the object. In this case, I used it for NLCs." He picked four features color-coded in the figure above (best seen in the full-sized version) and measured their positions. "The height of these NLCs ranged from 75.1 km (blue dot) to 78.6 km (red dot)," he says. "These results seem to be a little bit lower than the value of 83 km that is often referenced." http://www.spaceweather.com

CORONAL HOLE: Opening up like a zipper almost a million kilometers long, a vast coronal hole has appeared in the sun's northern hemisphere. NASA's Solar Dynamics Observatory took this picture of the UV-dark chasm on July 18th: Coronal holes are places in the sun's upper atmosphere where the magnetic field opens up and allows solar wind to escape. A broad stream of solar wind flowing from this particular coronal hole should reach Earth on July 19-20. In addition, NOAA forecasters say a CME could hit Earth's magnetic field late on July 18th. The combined impact of the CME and the incoming solar wind stream could cause some stormy space weather around Earth in the days ahead. NOAA forecasters estimate a 65% chance of polar geomagnetic storms on July 19-20. http://www.spaceweather.com/

Same here Botty, no haze or cloud and crystal clear deep blue skys,, 22.1c

There will be a change at some point towards the end of next week, where some big storms are possible. As to what extent is unknown at this point, as the models are struggling past Tuesday, Which is also a good indicator of some sort of change in the pattern. A very warm/ hot weekend, and start to the new working week coming up. By which time things should be much clearer. I think our mate with the glasses should be out with them chart's Karl

I closed my eye's and imagined for a moment..

Yes IHTR, im sure elevation and living in the sticks helps keep temps a little cooler here during the night, I keep every window open to keep cool, I really am looking forward to some sort of breakdown now. I dont want to spoil it for others, Im just crap in hot weather.. Plus im having to take a charity group of 22 up Snowdon for sunrise on Saturday night, im just glad it's through the night and not in the daytime heat. 3mm rain so far this month.

The end is nigh...

Dropped to pleasant 12,1c here last night, it's going to be a hot one today, no haze or cloud here this morning. Temp 15.2c

A warm dry night with clear skys and light winds, An overnight low of 12.1c. Currently. Crystal clear sky's this morning with no haze and wall to wall sunshine, As pit says, it's going to get unpleasant later today.... Temp 15,1c Wind N/E 2mph Humidity 89% Dp 13.8c

Im glad i live out in the sticks, must be awful living in built up area's in this heat. 21.4c here now,

You could touch 32c later.. cloud dependant.

27c here now in the shade. just touched 30c in the sun.

27c here in the shade, and 30c in the sun. Patchy cloud.