Greenland Melt Accelerating

Terra Daily ^ | 12/12/2007 | Staff Writers

[cogitator]

The 2007 melt extent on the Greenland ice sheet broke the 2005 summer melt record by 10 percent, making it the largest ever recorded there since satellite measurements began in 1979, according to a University of Colorado at Boulder climate scientist.

The melting increased by about 30 percent for the western part of Greenland from 1979 to 2006, with record melt years in 1987, 1991, 1998, 2002, 2005 and 2007, said CU-Boulder Professor Konrad Steffen, director of the Cooperative Institute for Research in Environmental Sciences. Air temperatures on the Greenland ice sheet have increased by about 7 degrees Fahrenheit since 1991, primarily a result of the build-up of greenhouse gases in Earth's atmosphere, according to scientists.

Steffen gave a presentation on his research at the fall meeting of the American Geophysical Union held in San Francisco from Dec. 10 to Dec. 14. His team used data from the Defense Meteorology Satellite Program's Special Sensor Microwave Imager aboard several military and weather satellites to chart the area of melt, including rapid thinning and acceleration of ice into the ocean at Greenland's margins.

Steffen maintains an extensive climate-monitoring network of 22 stations on the Greenland ice sheet known as the Greenland Climate Network, transmitting hourly data via satellites to CU-Boulder to study ice-sheet processes.

Although Greenland has been thickening at higher elevations due to increases in snowfall, the gain is more than offset by an accelerating mass loss, primarily from rapidly thinning and accelerating outlet glaciers, Steffen said. "The amount of ice lost by Greenland over the last year is the equivalent of two times all the ice in the Alps, or a layer of water more than one-half mile deep covering Washington, D.C."

The Jacobshavn Glacier on the west coast of the ice sheet, a major Greenland outlet glacier draining roughly 8 percent of the ice sheet, has sped up nearly twofold in the last decade, he said. Nearby glaciers showed an increase in flow velocities of up to 50 percent during the summer melt period as a result of melt water draining to the ice-sheet bed, he said.

"The more lubrication there is under the ice, the faster that ice moves to the coast," said Steffen. "Those glaciers with floating ice 'tongues' also will increase in iceberg production."

Greenland is about one-fourth the size of the United States, and about 80 percent of its surface area is covered by the massive ice sheet. Greenland hosts about one-twentieth of the world's ice -- the equivalent of about 21 feet of global sea rise. The current contribution of Greenland ice melt to global sea levels is about 0.5 millimeters annually.

The most sensitive regions for future, rapid change in Greenland's ice volume are dynamic outlet glaciers like Jacobshavn, which has a deep channel reaching far inland, he said. "Inclusion of the dynamic processes of these glaciers in models will likely demonstrate that the 2007 Intergovernmental Panel on Climate Change assessment underestimated sea-level projections for the end of the 21st century," Steffen said.

Helicopter surveys indicate there has been an increase in cylindrical, vertical shafts in Greenland's ice known as moulins, which drain melt water from surface ponds down to bedrock, he said. Moulins, which resemble huge tunnels in the ice and may run vertically for several hundred feet, switch back and forth from vertical to horizontal as they descend toward the bottom of the ice sheet, he said.

"These melt-water drains seem to allow the ice sheet to respond more rapidly than expected to temperature spikes at the beginning of the annual warm season," Steffen said. "In recent years the melting has begun earlier than normal."

Steffen and his team have been using a rotating laser and a sophisticated digital camera and high-definition camera system provided by NASA's Jet Propulsion Laboratory to map the volume and geometry of moulins on the Greenland ice sheet to a depth of more than 1,500 feet. "We know the number of moulins is increasing," said Steffen. "The bigger question is how much water is reaching the bed of the ice sheet, and how quickly it gets there."

Steffen said the ice loss trend in Greenland is somewhat similar to the trend of Arctic sea ice in recent decades. In October, CU-Boulder's National Snow and Ice Data Center reported the 2007 Arctic sea-ice extent had plummeted to the lowest levels since satellite measurements began in 1979 and was 39 percent below the long-term average tracked from 1979 to 2007.

[cogitator]

are already proclaiming 2007 as one of the hottest years ever.

It will probably end up 7th all-time (since the start of the instrumental record around 1880).

[cogitator]

Sorry for the double reply.

Also, the ‘record’ loss of sea ice from this summer has been replaced with a ‘record’ freeze of sea ice, earlier than normal.

Sea Ice Extent in the Arctic Ocean

"Record sea ice growth rates after a record low may sound surprising at first, but it is not completely unexpected. The more ice that survives the summer melt, the less open water there is for new ice to grow. When summertime ice extent hits a record low, on the other hand, large areas of open water provide room for the ice to grow once temperatures cool off enough. While summer warming of the upper ocean surface can cause wintertime sea ice regrowth to lag initially, as the fall season progresses and sunlight weakens, the rate of energy loss from the ocean increases. That heat loss coupled with a large area of open water creates ideal conditions for sea ice to form rapidly over large areas."

[cogitator]

Greenland's ice loss accelerating rapidly, gravity-measuring satellites reveal

"The estimates showed that 69 percent of the ice-mass loss in recent years came from eastern Greenland. Of the 57 cubic miles (239 cubic kilometers) of water mass lost on average each year, 39 cubic miles (164 cubic kilometers) were from the eastern shoreline. More than half of that eastern loss involved ice from the glacier complex in southeast Greenland."

There's your number for the whole ice sheet.

[cogitator]

Considering that Greenland had no ice over much of the SE and SW portions just 600 years ago, this isn't surprising.

Really? I would be interested in the source of this information.

Why do they think its called Greenland?

Because duplicitous but clever Erik the Red called it that. See point 8 in my profile.

[cogitator]

Funny - good comeback

If you are referring to Ms. Berry, it wasn't easy finding a picture from the movie that did not involve an orange bikini.

[nomorelurker]

“Why do you think its called Greenland?” Maybe just a marketing gimmick????

[G Larry]

Call me when it’s warm enough to start vinyards in Greenland.....again...you know, like the last time the V-8 engines warmed up that island sufficient to produce a great wine.

[Jotmo]

What, exactly, are we supposed to extrapolate from a 12 year trend snap shot of sea levels, from the billions of yeas of history of the planet? Eminent disaster?

[Tolerance Sucks Rocks]

Damn, your woman sure looks fine!

[BlazingArizona]

I am excited about this ice melt. We know Greenland used to be ice free and have vineyards. There is a chance some very good (and old) wine will be uncovered.

It was never 'ice free' in historical times, but during the Medieval Warm Period it was settled and farmed around fertile edges. If we get some more melting on this cycle, archaeologists will have a field day rediscovering Norse settlements.

[BigBobber]

Well, thanks for the link, but those data are based on gravimetric readings. I would be much more confident in actual measurements of the ice surface elevation, which is what the posted article is based on.

BTW, at the average rate of 239 cubic kilometers per year, it will take 12,000 years to melt the Greenland ice cap.

[Fred Nerks]

http://www.iceagenow.com/Volcanoes_in_Arctic_Ocean.htm

Underwater volcanic activity in the Arctic Ocean
far stronger than anyone ever imagined!
(This strongly confirms my belief that underwater volcanic activity
is heating the seas; not human activity.)

German-American researchers have discovered more hydrothermal activity at the Gakkel Ridge in the Arctic Ocean than anyone ever imagined.

“The Gakkel ridge is a gigantic volcanic mountain chain stretching beneath the Arctic Ocean. With its deep valleys 5,500 meters beneath the sea surface and its 5,000 meter- high summits, Gakkel ridge is far mightier than the Alps.”

Two research icebreakers, the “USCGC Healy” from USA and the German “PFS Polarstern,” recently joined forces in the international expedition AMORE (Arctic Mid-Ocean Ridge Expedition). In attendance were scientists from the Max Planck Institute for Chemistry and other international institutions.

The scientists had expected that the Gakkel ridge would exhibit “anemic” magmatism. Instead, they found “surprisingly strong magmatic activity in the West and the East of the ridge and one of the strongest hydrothermal activities ever seen at mid-ocean ridges.”

“The Gakkel ridge extends about 1800 kilometers beneath the Arctic Ocean from north of Greenland to Siberia, and is the northernmost portion of the mid-ocean ridge system.”
To their surprise, the researchers found high levels of volcanic activity. Indeed, magmatism was “dramatically” higher than expected.

Hydrothermal hot springs on the seafloor were also far more abundant than predicted. “We expected this to be a hydrothermally dead ridge, and almost every time our water measurement instrument came up, they showed evidence of hydrothermal activity, and once we even ‘saw’ an active hot spring on the sea floor,” said Dr. Jonathan Snow, the leader of the research group from the Max Planck Institute.

No wonder the ice is melting!

[Winniesboy]

If we get some more melting on this cycle, archaeologists will have a field day rediscovering Norse settlements.

Unlikely, at least not for this reason, since the coastal fringe always thaws every summer anyway, and possible early settlement sites have thus always been available for excavation. The two main settlements have already been well studied by the Danes.

[justa-hairyape]

While summer warming of the upper ocean surface can cause wintertime sea ice regrowth to lag initially, as the fall season progresses and sunlight weakens, the rate of energy loss from the ocean increases.

So which of the following is more likely to be true ?

A - Warmer water caused massive ice melting and then massive ice freezing.

B - Warmer water caused massive ice melting and then weaker sunlight caused massive ice freezing ?

C - Increased sunlight caused massive ice melting and then decreased sunlight caused massive ice freezing ?

[cogitator]

Damn, your woman sure looks fine!

Alright, there's out of my league and then there's The Impossible Dream. What category do you think she's in?

[cogitator]

Eminent disaster?

Well, perhaps not that distinguished, but cause for concern when all the trends are noted.

[cogitator]

BTW, at the average rate of 239 cubic kilometers per year, it will take 12,000 years to melt the Greenland ice cap

If you read the concerns of the climatologists, one of them is that the dynamics of ice sheet decline (for lack of a more descriptive word) are not well understood. Read closely, and you'll find many references to the movement of meltwater under the ice sheets lubricating their movement. So the potential for a rapid acceleration of ice loss is on their minds.

Ever see this?

Description:

Collapse of Antarctic Ice Shelf Unprecedented

Now, I know continental ice sheets and floating ice shelves are different things. My point is that the Larsen ice shelf was fairly solid until the month in 2002 when it wasn't -- and then it was gone.

Food for thought, maybe.

[Grizzled Bear]

Planetary Bovine Scatology!

Sorry.

I’ll go sit down now.

[<1/1,000,000th%]

Really? I would be interested in the source of this information.

I don't remember where I saw it and I can't seem to find any reference to it in a quick search.

You've got some very interesting links though. Thanks for pointing those out.

[steelyourfaith]

~~AGW ™ ping~~