“This is the first time we’ve seen waters this warm in any of the fjords in Greenland,” says Straneo. “The subtropical waters are flowing through the fjord very quickly, so they can transport heat and drive melting at the end of the glacier.”

Greenland’s ice sheet, which is two-miles thick and covers an area about the size of Mexico, has lost mass at an accelerated rate over the last decade.  The ice sheet’s contribution to sea level rise during that time frame doubled due to increased melting and, to a greater extent, the widespread acceleration of outlet glaciers around Greenland.

While melting due to warming air temperatures is a known event, scientists are just beginning to learn more about the ocean’s impact — in particular, the influence of currents — on the ice sheet.

“Among the mechanisms that we suspected might be triggering this acceleration are recent changes in ocean circulation in the North Atlantic, which are delivering larger amounts of subtropical waters to the high latitudes,” says Straneo.  But a lack of observations and measurements from Greenland’s glaciers prior to the acceleration made it difficult to confirm.

The research team, which included colleagues from University of Maine, conducted two extensive surveys during July and September of 2008, collecting both ship-based and moored oceanographic data from Sermilik Fjord — a large glacial fjord in East Greenland.

Sermilik Fjord, which is 100 kilometers (approximately 62 miles) long, connects Helheim Glacier with the Irminger Sea. In 2003 alone, Helheim Glacier retreated several kilometers and almost doubled its flow speed.

Deep inside the Sermilik Fjord, researchers found subtropical water as warm as 39 degrees Fahrenheit (4 degrees Celsius). The team also reconstructed seasonal temperatures on the shelf using data collected by 19 hooded seals tagged with satellite-linked temperature depth-recorders. The data revealed that the shelf waters warm from July to December, and that subtropical waters are present on the shelf year round.

“This is the first extensive survey of one of these fjords that shows us how these warm waters circulate and how vigorous the circulation is,” says Straneo. “Changes in the large-scale ocean circulation of the North Atlantic are propagating to the glaciers very quickly — not in a matter of years, but a matter of months. It’s a very rapid communication.”

Straneo adds that the study highlights how little is known about ocean-glacier interactions, which is a connection not currently included in climate models.

“We need more continuous observations to fully understand how they work, and to be able to better predict sea-level rise in the future,” says Straneo.

The paper was chosen for advanced online publication Feb. 14, 2010, by Nature Geosciences; it will also appear in the March 2010 printed edition of the journal. Co-authors of the work include WHOI postdoc David Sutherland (now of University of Washington), Gordon Hamilton and Leigh Stearns of the Climate Change Institute, University of Maine, Fraser Davidson and Garry Stenson of the Department of Fisheries and Oceans, St. John’s, Newfoundland, Mike Hammill of the Department of Fisheries and Oceans, Mont-Joli, Quebec, and Aqqalu Rosing-Asvid of the Department of Birds and Mammals, Greenland Institute of Natural Resources. Canadian and Greenlandic colleagues contributed valuable data on the shelf, from tagged seals.

Funding for this research was provided by the National Science Foundation, WHOI’s Ocean and Climate Change Institute Arctic Research Initiative, and NASA’s Cryosperic Sciences Program.

 Woods Hole Oceanographic Institution New Release: Team finds subtropical waters flushing through Greenland fjord

Journal of Climate
Volume 22, Issue 14 (July 2009)
Article: pp. 4029–4049

The Abstract states:

Meteorological station records and regional climate model output are combined to develop a continuous 168-yr (1840–2007) spatial reconstruction of monthly, seasonal, and annual mean Greenland ice sheet near-surface air temperatures. Independent observations are used to assess and compensate for systematic errors in the model output. Uncertainty is quantified using residual nonsystematic error. Spatial and temporal temperature variability is investigated on seasonal and annual time scales. It is found that volcanic cooling episodes are concentrated in winter and along the western ice sheet slope. Interdecadal warming trends coincide with an absence of major volcanic eruptions. Year 2003 was the only year of 1840–2007 with a warm anomaly that exceeds three standard deviations from the 1951–80 base period. The annual whole ice sheet 1919–32 warming trend is 33% greater in magnitude than the 1994–2007 warming. The recent warming was, however, stronger along western Greenland in autumn and southern Greenland in winter. Spring trends marked the 1920s warming onset, while autumn leads the 1994–2007 warming. In contrast to the 1920s warming, the 1994–2007 warming has not surpassed the Northern Hemisphere anomaly. An additional 1.0°–1.5°C of annual mean warming would be needed for Greenland to be in phase with the Northern Hemispheric pattern. Thus, it is expected that the ice sheet melt rates and mass deficit will continue to grow in the early twenty-first century as Greenland’s climate catches up with the Northern Hemisphere warming trend and the Arctic climate warms according to global climate model predictions.

The full paper can be found here.

This is another paper that demonstrates that the Arctic warming in the early part of the 20th Century was greater (by one-third) that the current warming, but it is written in an AGW and climate model friendly way.

H/T: The Reference Frame

Controversy has swirled around the map since it came to light in the 1950s, many scholars suspecting it was a hoax meant to prove that Vikings were the first Europeans to land in North America — a claim confirmed by a 1960 archaeological find.

Doubts about the map lingered even after the use of carbon dating as a way of establishing the age of an object.

“All the tests that we have done over the past five years — on the materials and other aspects — do not show any signs of forgery,” Rene Larsen, rector of the School of Conservation under the Royal Danish Academy of Fine Arts, told Reuters.

He presented his team’s findings at an international cartographers’ conference in the Danish capital Friday.

The map shows both Greenland and a western Atlantic island “Vinilanda Insula,” the Vinland of the Icelandic sagas, now linked by scholars to Newfoundland where Norsemen under Leif Eriksson settled around AD 1000.

Yahoo/Reuters News: ‘Vinland Map of America no forgery, expert says’

CRN comment: If the map is genuine it provides evidence of a relatively ice-free Arctic in the Medieval Warm Period that allowed the Vikings to sail unimpeded to North America.

The Greenland and Antarctica ice sheets are melting, but the amounts that will melt and the time it will take are still unknown, according to Richard Alley, Evan Pugh professor of geosciences, Penn State.

In the past, the Greenland ice sheet has grown when its surroundings cooled, shrunk when its surroundings warmed and even disappeared completely when the temperatures became warm enough. If the ice sheet on Greenland melts, sea level will rise about 23 feet, which will inundate portions of nearly all continental shores. However, Antarctica, containing much more water, could add up to another 190 feet to sea level.

“We do not think that we will lose all, or even most, of Antarctica’s ice sheet,” said Alley. “But important losses may have already started and could raise sea level as much or more than melting of Greenland’s ice over hundreds or thousands of years,” Alley told attendees today (Feb 16) at the annual meeting of the American Association for the Advancement of Science.

Warming is expected to cause more precipitation on Greenland and Antarctica, adding snow. Previously, many scientists suggested that this would offset increasing melting. However, recent studies show that the ice sheets on both Greenland and in Antarctica are melting faster than the snow is replacing the mass.

A number of things can contribute to the increased rate of melting in Greenland and Antarctica. Large lakes of water on the ice in Greenland pose a problem. This water, by wedging open a crack or crevasse in the ice, quickly flows through to the bottom, melting the bottom of the ice sheet and causing it to move more rapidly toward the ocean. Observers have seen lakes on the Greenland ice sheet drain at the speed of Niagara Falls.

All ice sheets spread due to their large mass, but friction from the rocks beneath slows the ice’s motion. Water beneath the ice allows the ice to move more rapidly.

“Right now, the center of the Greenland ice sheet is frozen to the rocks,” says Alley. “If the melt water moves inland as the world warms and gets to the bottom, it will thaw the bottom and unstick the ice from the rocks.”

Another contributor to the melting ice sheets is the warming of the ocean. When ice shelves — ice still connected to the ice sheet but floating over water — melt, they also cause the ice sheet to flow faster. In Greenland, the Jakobshavn ice shelf has retreated more than 5 miles since 1992. Rocks and cliffs on the sides of fiords or inlets slow the seaward movement of the ice shelves. If these shelves break up and melt, the ice streams behind them move more rapidly.

Ice shelf failures have also occurred on Antarctica where, for example, most of the Larsen B ice shelf disintegrated in March of 2002 and increased the rate of ice stream flow eight times.

“Water temperature is more important than air temperature in melting the ice shelves,” says Alley. “However, both contribute.”

Warmer oceans, caused by general global warming or local events can trigger more breakups of ice shelves and faster flow of ice streams in Antarctica. In Greenland, sustained increase in temperatures of only a few degrees will remove the ice.

Alley believes he knows the direction to go to gain a better understanding of the ice sheets, how they work and the effect they have on climate change. Although those who study ice sheets have long modeled ice sheet behavior, simulations of the whole earth system typically have not included ice sheets along with the atmosphere, oceans and clouds, in their models. Past atmospheric modelers usually treated the ice sheets simply as white mountains.

“They are not white mountains and they need to be modeled,” said Alley. “We need to have them in the models to figure out how the system works.”

Alley notes that a collaboration of government and academic scientists created the atmospheric and ocean models, but collaborations to model the ice are only just being developed.

Embargoed for release: 16-Feb-2009 10:30 ET
(16-Feb-2009 15:30 GMT)

Ice loss in Greenland has had some climatologists speculating that global warming might have brought on a scary new regime of wildly heightened ice loss and an ever-faster rise in sea level. But glaciologists reported at the American Geophysical Union meeting that Greenland ice’s Armageddon has come to an end.

So much for Greenland ice’s Armageddon. “It has come to an end,” glaciologist Tavi Murray of Swansea University in the United Kingdom said during a session at the meeting. “There seems to have been a synchronous switch-off” of the speed-up, she said. Nearly everywhere around south east Greenland, outlet glacier flows have returned to the levels of 2000. An increasingly warmer climate will no doubt eat away at the Greenland ice sheet for centuries, glaciologists say, but no one should be extrapolating the ice’s recent wild behavior into the future.

Kerr didn’t cover the Knappeneberger et al (of World Climate Report) presentation entitled, ‘A Reconstructed 1784-2007 Time Series of Greenland Melt Extent.’

The Abstract states:

Total melt on the Greenland ice sheet has been rising over the past several decades. The melt extent observed in 2007 was the greatest on record according to several satellite-derived indices of Greenland melt. Observed melt extent across the Greenland ice sheet has been shown to be strongly related to summer station temperatures from locations along Greenland’s coastal periphery, as well as to variations in the circulation of the atmosphere across the North Atlantic. We exploit these relationships with historical temperature and circulation observations to develop a 224-yr reconstructed history of annual Greenland melt extent from the late 18th century to 2007. This reconstruction allows us to put recent melt, particularly 2007, into a historical perspective and compare current melt to the well-known warm period in the early half of the 20th century. Our reconstruction indicates that the melt observed since the late 1990s is likely among the highest extents to have occurred since the late 18th century, although recent values are not statistically different from those common during the period 1923-1961, a time when summer temperatures along the southern coast of Greenland were similarly high as those experienced in recent years. The reconstruction indicates that if the current trend toward increasing melt extent continues, total melt across the Greenland ice sheet will exceed historic values of the past two and a quarter centuries.

The Abstract states:

The recent marked retreat, thinning and acceleration of most of Greenland’s outlet glaciers south of 70° N has increased concerns over Greenland’s contribution to future sea level rise. These dynamic changes seem to be parallel to the warming trend in Greenland, but the mechanisms that link climate and ice dynamics are poorly understood, and current numerical models of ice sheets do not simulate these changes realistically. Uncertainties in the predictions of mass loss from the Greenland ice sheet have therefore been highlighted as one of the main limitations in forecasting future sea levels. Here we present a numerical ice-flow model that reproduces the observed marked changes in Helheim Glacier, one of Greenland’s largest outlet glaciers. Our simulation shows that the ice acceleration, thinning and retreat begin at the calving terminus and then propagate upstream through dynamic coupling along the glacier. We find that these changes are unlikely to be caused by basal lubrication through surface melt propagating to the glacier bed. We conclude that tidewater outlet glaciers adjust extremely rapidly to changing boundary conditions at the calving terminus. Our results imply that the recent rates of mass loss in Greenland’s outlet glaciers are transient and should not be extrapolated into the future.

According to the BBC News website, the ducks are an experiment to see how melt waters find their way to the base of the ice sheet.

It was hoped the ducks would flow along subglacial channels and eventually pop out into the sea. They may still, but nothing has been seen of them so far.

“We haven’t heard anything from them yet,” said Nasa’s Alberto Behar. “If somebody does find one, it will be a great breakthrough for us.”

BBC News website: ‘Nasa ducks dive under Greenland ice’