Why Southeast Greenland's glaciers have slown down since 2005
I'm in San Francisco for the annual meeting of the American Geophysical Union, the world's largest gathering of climate scientists. I saw ten or so great talks yesterday (and five really boring ones!) Here's a summary of the the most interesting talk I heard yesterday:
If you plan on owning ocean front property after the year 2050, you should pay close attention to the glaciers In Greenland. Greenland holds enough ice to raise global sea level by over 20 feet (6.5 meters), should its ice cap completely disintegrate--though such an event would likely take centuries to occur. Still, should the climate warm 2°C or more this century, partial melting of the Greenland Ice Sheet could readily raise global sea level by a meter or more by 2100. That's why scientists reacted with concern during 2003 - 2005, when all of the glaciers in southeastern Greenland accelerated in synchrony to speeds 30% to 210% faster than they had flowed in 1996. As they sped up, the glaciers began dumping huge amounts of ice into the ocean off the coast of southeast Greenland, more than doubling Greenland's contribution to global sea rise, to .57 mm/year. Would the glaciers keep accelerating, bringing about an increasing disintegration of the Greenland Ice Sheet? Nobody knew, since computer models of glacial dynamics were (and still are) in a primitive state.
Figure 1. Helheim Glacier in southeast Greenland, in three images captured in 2004, 2005, and 2006. The glacier accelerated significantly in 2005, and the face of the glacier retreated 5 km inland (middle frame) compared to 2004. However, by the summer of 2006, the acceleration ceased, the the glacier returned back to its 2004 position. Image credit: Ian Howat, University of Washington.
Well, it turned out that 2005 was the peak of the glacial acceleration event. The glaciers in southeast Greenland have returned to where they were eight or nine years ago--still causing a net loss of mass that is raising global sea level, but not as fast as in 2003 - 2005. In a talk titled, "Ocean regulation of glacier dynamics in south-east Greenland and implication for ice sheet mass changes", Tavi Murray and colleagues from the UK's Swansea University presented a plausible theory for why this strange synchronous speed-up and slow-down occurred. Using satellite, aircraft, and surface observations, the researchers found that air temperatures in the region did not vary much over 2003 - 2005 (Figure 2). Thus, a major increase in temperature could be ruled out as the cause of the glacier surge. However, study of the ocean temperatures near the coast revealed strong clues that ocean currents were responsible for the surge.
Figure 2. Ocean currents off the east coast of Greenland feature the cold East Greenland Coastal Current flowing north to south (white arrows) and the warm Irminger Current flowing south to north (red arrows). Image credit: Arctic Climate Impact Assessment.
Ordinarily, the southeast coast of Greenland features a cold water current flowing north to south, called the East Greenland Coastal Current (EGCC). Much of the cold water for this current is supplied by melting of the 14 glaciers in southeast Greenland that empty into the sea (two of these glaciers, Kangerdlugssuaq and Helheim, represent 35% of east Greenland's total glacial discharge). A few hundred kilometers offshore, a warm water current called the Irminger Current flows the opposite direction, bringing warm water from the North Atlantic northward. In 2003, it happened that weather conditions over Greenland brought an unusually low amount of run-off of precipitation. With little new mass pushing the glaciers seaward, the glaciers responded by greatly reducing the amount of ice they dumped into the ocean by the shore. As a result, the East Greenland Coastal Current slowed down and warmed, which allowed the warm Irminger Current to advance towards the coast, warming the coastal waters even more. All that warm water near the coast began melting the glaciers where they reached the sea, causing the glaciers all along the southeast coast of Greenland to accelerate and rapidly thin between 2003 - 2005. By 2006, the thinning glaciers had dumped so much new ice into the ocean near the coast that the waters cooled and the East Greenland Coastal Current re-established itself. This cooled the glaciers at their marine termination points and slowed down the glacial surge, putting the glaciers back where they had been before 2003. This is a classic example of a negative feedback process--a change in weather conditions which generates a response, but the response creates conditions that tend to dampen the response.
Figure 3. Average temperatures for the only station in southeast Greenland with a century-long temperature record, Angmagssalik (called Ammassalik on the map in Figure 2). Temperatures in southeast Greenland during the 1930s and 1940s were similar to today's temperatures, suggesting that glacial surges like we witnessed in 2005 may have also occurred in the 1930s and 1940s, before we had monitoring capability. Image credit: NASA Goddard.
Commentary
As I commented in my previous post, Arctic sea ice loss appears to have created a new atmospheric circulation pattern that brings more warm air in the Arctic, creating a positive feedback loop that causes even more sea ice loss. This positive feedback loop was a bad news surprise that our climate models did not predict. Now we have evidence of a good news surprise that no model predicted--a negative feedback loop that acts to keep the southeast portion of Greenland's Ice Sheet from runaway glacial acceleration. We can expect many more surprises--good and bad--over the coming decades, as our climate responds to the huge shove human activities are giving it.
Ricky Rood in Copenhagen
Our Climate Change expert, Dr. Ricky Rood, is in Copenhagen for the COP15 climate change treaty negotiations. His latest post, called Have you no sense of decency, sir, at long last? makes for very interesting reading on how the U.S. is "wasting its intellect and time on disruptions designed to play to people at home".
Next post
I'll have another post from the AGU meeting Thursday or Friday this week.
Jeff Masters
Reader Comments
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Link 18Z GFS model current through 12-22-09 below:
Link
This El Nino is warming the C PAC. So the Sub-Tropical Jet is being supercharged with warm, moist, tropical mositure, while Arctic intrusions still take place over Canada and the CONUS from time to time, producing prolific rain/snow producers around the counrty. Now with the NEG AO and NEG NAO, even more cold air is going to be dumped into the US, producing he possibilities for S Plains, SE US, Mid Atlantic, NE and New England Snowstorms!!!
READ LINK :o) And enjoy your snowstorm!!!
Link
Howdy, folks!
For something as uncommon as snow in the "south", I would not pay much attention to any model more than 5 days out. Also, the 18z GFS is the least accurate of all the model runs. 0z and 12z are usually the most accurate, as they have the most recent sounding information added in. 06z' uses data that is at least 6 hours old, and 18z uses data that is anywhere from 6-18hr old.
CMC brings cold air, but then backs it off slowly from Florida, but remains below average.
It's still VERY early, but here is an early look at the
SPECIAL Graphics Update:
2010 Hurricane Season Names
Shouldnt it be the 2004 names retired? Charley, Frances, Ivan, Jeanne?
It is that graphic is wrong.
I enjoy reading your entries, as they are very detailed and very intersting,
Do you have any links you could share with me, so I can see the raw details!
P.S. Please join us in Weather Chat! Thank you!
fixed now....sorry about the error
I am here in Raleigh, and its about time it REALLY SNOWED! Woohooo.
Is there a model output showing expected snowfall totals?
URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
507 PM EST WED DEC 16 2009
...SIGNIFICANT SNOW POSSIBLE FRIDAY THROUGH SATURDAY AFTERNOON...
.A COASTAL STORM SYSTEM IS EXPECTED TO SPREAD PRECIPITATION OVER
THE MOUNTAINS FRIDAY INTO SATURDAY. TEMPERATURES ACROSS THE
NORTHERN NORTH CAROLINA MOUNTAINS AND ADJACENT FOOTHILLS ARE
FORECAST TO REMAIN COLD ENOUGH TO SUPPORT MAINLY SNOWFALL...WITH
PERIODS OF SLEET AND FREEZING RAIN. BY SATURDAY AFTERNOON...STORM
TOTAL SNOWFALL IS EXPECTED TO RANGE FROM 3 TO 6 INCHES ACROSS THE
NORTHERN NORTH CAROLINA MOUNTAINS TO 1 TO 4 INCHES ACROSS THE
FOOTHILLS ADJACENT TO THE EAST FACING MOUNTAIN SLOPES.
NCZ033-049-050-053-065-501>507-509-170900-
/O.NEW.KGSP.WS.A.0008.091218T1100Z-091219T2300Z/
AVERY-YANCEY-MITCHELL-BUNCOMBE-HENDERSON-CALDWELL MOUNTAINS-
GREATER CALDWELL-BURKE MOUNTAINS-GREATER BURKE-MCDOWELL MOUNTAINS-
EASTERN MCDOWELL-RUTHERFORD MOUNTAINS-POLK MOUNTAINS-
INCLUDING THE CITIES OF...NEWLAND...SPRUCE PINE...ASHEVILLE...
HENDERSONVILLE...LENOIR...MORGANTON...MARION...LAKE LURE
507 PM EST WED DEC 16 2009
...WINTER STORM WATCH IN EFFECT FROM FRIDAY MORNING THROUGH
SATURDAY AFTERNOON...
THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED
A WINTER STORM WATCH...WHICH IS IN EFFECT FROM FRIDAY MORNING
THROUGH SATURDAY AFTERNOON.
LIGHT SNOW...WITH PERIODS OF SLEET AND FREEZING RAIN...WILL
SPREAD NORTH ACROSS THE NORTH CAROLINA NORTHERN MOUNTAINS AND
FOOTHILLS ON FRIDAY. BY FRIDAY AFTERNOON...PRECIPITATION RATES
WILL INCREASE AS DEEP LIFT ASSOCIATED WITH A COASTAL LOW SWEEPS
OVER THE REGION. THE LOW WILL BEGIN TO DEPART ON
SATURDAY...RESULTING IN A GRADUAL DECREASE IN PRECIPITATION
RATES. TEMPERATURES WILL COOL FRIDAY EVENING AND WILL LIKELY
REMAIN NEAR FREEZING THROUGH MID DAY SATURDAY.
BY SATURDAY AFTERNOON...STORM TOTAL SNOWFALL IS EXPECTED TO RANGE
FROM 3 TO 6 INCHES ACROSS THE NORTHERN NORTH CAROLINA MOUNTAINS TO
1 TO 4 INCHES ACROSS THE FOOTHILLS ADJACENT TO THE EAST FACING
MOUNTAIN SLOPES.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.
&&
$$
NED
Awww, will maybe so much snow won't happen in Raleigh. It looks like its going to dump all the snow west of the piedmont and be concentrated in the foothills (maybe a little snow mixing with rain here).
Thanks for the map, looks like we're on the fence out here (really sharp edge between 1 to 6 inches). I've seen these type of events before. If I remember right, one time here we got 22 inches of snow in January 2000 (the most ever in Raleigh), and everywhere else around us got a lot less. Then there was one storm not longer after that where Raleigh was expecting 18 inches in the forecast. Instead, the forecast was a total failure, and Raleigh got zero while literally 1 or 2 counties just to our east got a foot!
Hey, lil' ol' us is south of the Mason-Dixon line! Try telling that to a Texas cop, though. :(
Yea. With the teleconnections and the positive height anomalies I think the storm will come further west than the GFS and ECMWF and give several Mid-Atlantic states snow but time will tell.
The 18Z GFS model output for the possible east coast storm just updated the snow fall totals. It is becoming a much better storm for the big cities.
I tihnk it's great where it is right now, and actually may be a bit too far west.
As of now, I don't think the storm will come enough west to have a major impact on New England and Long Island because of the jet stream but we will see.
I understand that the 00, 06 and 12Z GFS runs are more reliable! I hear the 18Z run uses data that is about 12 hrs old! Ridiculous to use a super-computer to download a bunch of antique information, then call it a forecast! Come on NWS, you're better than THAT!!
I hope the E Coast has a white and snowy Fr-Su. Maybe the rest of us S Plains and SE US folks will get a shot of snow next week. We'll take whatever we can get!
from that jet stream picture (12Z GFS model, 96 hours out), it seems clear that the storm would have minor impacts at best on new england and long island.
However, from the latest gfs picture (18Z GFS model, 90 hours out), the NW part of the jet stream is starting to move more to the NW. Granted it is a small move (about 100 miles or so), but it may be enough to cause a substantial increase in snow for some of the big cities, as shown in the 18Z GFS.
The key to any snow in the big cities is the placement of the 1126 heights signature in eastern canada. Further to the se, the jet storm kinks more to the north, the surface low is much stronger, and we have a major east coast storm. If the 1126 heights signature stays where it is placed on the 12Z GFS, then yes, there will be very minor affects for just about everyone north of 40N.
In any case, I don't expect a final solution to be evident for those from Raleigh to Boston until mid day friday.
what about it?
Around 1000mb
What St. Simmons said.
is this christmas?
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