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
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Doing great! Won a Nintendo Wii at the Christmas party yesterday and the bowling game is rather addictive! Glad to hear you're having a good day. How is the weather looking? Still cold?
RFDS(Royal Flying Doctors Service) fly in to evacuate man, 26, injured in Cyclone Laurence roof fall
A 26-YEAR-old man has been seriously injured and is being flown to Perth by Royal Flying Doctor after being blown off a roof by high winds from Tropical Cyclone Laurence.
The man, who will be evacuated by Royal Flying Doctor, appears to have damage to his spine and hip and has a broken arm.
The RFDS will be sending its Rio Tinto Life Flight jet and a medical crew from Perth to evacuate the badly injured patient from Kununurra, after Tropical Cyclone Laurence forced the RFDS Derby base into lock down.
RFDS aircraft at the Derby base which normally would have been used to pick up the man from Kununurra hospital and transfer him to Darwin have been locked down due to strong wind gusts and heavy rain.
However, the RFDS Jet will fly into the cyclonic weather, leaving Perth airport at about 10.30am and arriving in Kununurra at about 1.30pm.
The crew will then decide whether to transfer the injured man to Darwin or Perth, depending on weather conditions.
“If we didn’t have the Rio Tinto Life Flight jet this badly injured man would have been stuck at Kununurra,” said RFDS Medical Director, Stephen Langford.
“Instead he’ll be transferred to specialist care in a matter of hours.”
All clear for Derby as storm moves south
Cyclone Laurence weakened today but authorities are still warning residents in the path of its destructive winds - and the chance it could restrengthen in coming days.
An all clear was issued for the town of Derby about 6.30pm as the cyclone continued on its southerly track, weakening to a category 1 storm. Communities at Cape Leveque, One Arm Point, Djarindjin, Lombadina and nearby were also given the all clear.
At 5 pm Laurence, Category 1, was estimated to be 85km east of Derby and moving south at five kilometres per hour.
It had moved slowly over land east of Derby and had gradually weakened.
Gales with gusts to 100 kilometres per hour are possible close to the cyclone centre, FESA said.
Gales are possible near the centre overnight as Laurence moves to the south or southwest.
Heavy raid is expected to continue over the northwest Kimberley.
Daily rainfall totals in excess of 100mm are expected with isolated falls as high as 300mm possible near the path of the cyclone.
``It's really slowed down overnight but there's still a possibility of destructive winds,'' James Ashley, a forecaster at Perth's Tropical Cyclone Warning Centre told AAP on Thursday.
``Cyclones gradually weaken over land and this will be no exception but it's still strong enough to do some damage.''
``People shouldn't get complacent about it.''
Wind gusts of up to 155km/h are still possible close the the cyclone centre, he said.
A cyclone watch is current for Beagle Bay to Bidyadanga, including Broome, and also extending inland to Fitzroy Crossing.
Laurence, the first cyclone of the season off the WA coast, formed in the Timor Sea on Sunday.
So now is our chance to talk about her all we want and all she can do is hurl insults at her monitor.
I'll start.
Is AIM a cougar?
Several communities in Western Australia's Kimberley region remain on red alert as a rapidly weakening cyclone moves inland.
Emergency services were worried as the small but intense Tropical Cyclone Laurence intensified to a category 5 system yesterday.
With gusts up to 285 kilometres per hour, there were fears the destructive winds could hit remote communities.
But the storm threaded its way past Kuri Bay before making landfall last night about 100km north of Derby.
It has now been downgraded to a category 2 cyclone but still has winds up to 155kph.
Residents in Derby, Koolan Island and Cockatoo Island have been warned to take shelter.
Cyclone Laurence is expected to sweep inland past Derby this afternoon, weakening to a category 1 as it reaches the town of 4,500.
Lee Vallance from the Fire and Emergency Services Authority (FESA) has warned residents to expect damage to the town.
"It just means they should expect some kind of impact from the cyclone and to seek shelter," he said.
FESA is warning people to remain indoors, keep windows and doors closed, disconnect electrical appliances and turn off gas supply valves.
Motorists are being asked to park vehicles in sheltered areas with the handbrake on.
The town's shops and schools will stay closed until the alert is lifted.
FESA's Rob Cox says parts of the highway between Derby, Fitzroy Crossing and Broome will be closed until the all-clear is issued.
"People coming from Port Hedland need to stop at Roebuck Roadhouse or don't travel, and people in Fitzroy Crossing need to stay in Fitzroy Crossing," he said.
"The people in Derby need to stay in Derby, until through the ABC or through the media there is an advice from BOM [the weather bureau] that there is an all-clear."
Cyclone Laurence has already brought heavy rains and destructive winds to communities and cattle stations across the north Kimberley.
But Gordon Tiddums from FESA says Kuri Bay was relatively unscathed.
"Really there's no damage, just trees down. They've had some strong gusts of wind but no buildings destroyed," he said.
Linda Pearson from Theda Station says the property received 175 millimetres of rain in 24 hours and she expects to be stranded for several days.
"We've just had a very heavy storm. You can't go anywhere, literally, because the water on the roads is too deep," she said.
"We've got water above our lawns, our septic tanks are flooding, our roads are now rivers and our driveway is a river."
- ABC
AIM??? who's she?
Windows were blown out as lightning struck an Adelaide house during thunderstorms.
An elderly Adelaide couple is in shock after their house at Hallett Cove in the southern suburbs was hit.
Jan Nittsjo was in bed and his wife Brigitte was watching television when the bolt struck their TV antenna just after 9:30pm on Wednesday.
The ceiling caved in, hitting Mrs Nittsjo on the head and she screamed.
The couple says there was a deafening bang and the bolt shook the house, shorting electrical wiring and leaving a large hole in the roof.
Mrs Nittsjo says she was momentarily deafened by the noise and Mr Nittsjo says he did not know what to think at the time.
"It was terrible," he told reporters. "She was watching TV and I was listening to the radio in the bedroom and all of a sudden 'bang', the ceiling fell down, all the paintings and things fell off."
The couple is now cleaning up the house but making plans to go elsewhere for Christmas.
The damage bill is put at $100,000.
- ABC
AwakeInMaryland
Awake in Maryland
A little chilly; high to day around 50 or so but the wind is calm.
That bowling game is addictive, isn't it?
Not that I've seen, and it's irritating me. Title should be "SLOWED DOWN." "SLOWN" isn't a word!
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