Global Warming Pioneer Says Melting Ice May Cool North Atlantic

James Hansen says that the melt rate of Greenland's Ice sheet is doubling every ten, or even every 5 years. Thermohaline circulation in the Atlantic is expected to slow by 2075 as a result. Atlantic Ocean storms may intensify due to more cold water staying on the surface in the north Atlantic while the south Atlantiac continues to heat up, creating a stronger gradient.

Greenland ice melting at an expanding pace may begin cooling the North Atlantic and increasing the severity of storms by 2075, said James Hansen, the former NASA scientist who raised concerns about global warming in the 1980s.

“If we stay on this path where the rate of mass loss from Greenland doubles every 10 years, we would get to a situation by about 2075 or 2080 where the mass loss is so fast that it causes the whole North Atlantic to be colder,” Hansen said in London.

The findings are from computer models using current rates of ice melt and will be detailed in a paper that Hansen plans to finish writing in the summer, he said on Thursday in an interview.

Inflows of cold, fresh water from Greenland would slow deep currents that carry cold water south, cooling the North Atlantic as tropical waters get warmer, Hansen said. That would increase a “temperature gradient” that’s conducive to stronger storms.

“It could happen sooner” than 2075, Hansen said. “If you look at how fast the mass loss is increasing, it looks like the doubling time is between five and 10 years.”

The findings add to research showing the system of Atlantic currents that channels the warm Gulf Stream to the northeast and moves colder, deeper waters south may slow this century because of climate change. [emphasis mine]


This April 20, 2013 NASA handout image shows Saunders Island and Wolstenholme Fjord with Kap Atholl in the background seen during an IceBridge survey flight nea Qaasuitsup, Greenland. Sea ice coverage in the fjord ranges from thicker, white ice seen in the background, to thinner grease ice and leads showing open ocean water in the foreground.

Tags: Greenland melt, thermohaline circulation decline

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An overlooked factor will increase the rate of Greenland Ice Sheet melt: lakes on the glacier will move further inland.

Migrating 'supraglacial' lakes could trigger future Greenland ice loss

... the future distribution of lakes that form on the ice sheet surface from melted snow and ice -- called supraglacial lakes -- have been simulated for the first time.
Previously, the impact of supraglacial lakes on Greenland ice loss had been assumed to be small, but the new research has shown that they will migrate farther inland over the next half century, potentially altering the ice sheet flow in dramatic ways.
Until now, supraglacial lakes have formed at low elevations around the coastline of Greenland, in a band that is roughly 100 km wide. At higher elevations, today's climate is just too cold for lakes to form.

Since the 1970s, the band in which supraglacial lakes can form on Greenland has crept 56km further inland. From the results of the new study, the researchers predict that, as Arctic temperatures rise, supraglacial lakes will spread much farther inland -- up to 110 km by 2060 -- doubling the area of Greenland that they cover today.

Dr Leeson said: "The location of these new lakes is important; they will be far enough inland so that water leaking from them will not drain into the oceans as effectively as it does from today's lakes that are near to the coastline and connected to a network of drainage channels."

"In contrast, water draining from lakes farther inland could lubricate the ice more effectively, causing it to speed up." [emphasis mine]

Supraglacial lakes on the Greenland ice sheet can be seen as dark blue specks in the center and to the right of this satellite image.

Greenland's ice sheet continues to surprise us:

  •  liquid water can remain near the surface through Winter
  •  large "lenses" of solid ice hidden in the snow can modify water dynamics during a melt

Surprising findings in Greenland’s melt dynamics

Across wide areas of Greenland researchers are finding, that water can remain liquid, hiding in layers of snow just below the surface, even through cold, harsh winters. The discoveries—made by teams including Rick Forster of the University of Utah and Lora Koenig of the National Snow and Ice Data Center—mean that scientists seeking to understand the future of the Greenland ice sheet need to account for relatively warm liquid water retained in the ice. This discovery also means that the surface hydrologic system, once thought to freeze solid during the winter, can remain active year-round.

...these findings present a picture of water remaining just below the surface year round around nearly the entire perimeter of the ice sheet. “More year-round water means more heat is available to warm the ice,” Koenig said. “Simply put, for ice sheet stability, lots of water is not good.”

… their drill hit something completely unexpected: dense layers of ice more than 15 feet thick just under the surface. This high on the ice, the researchers expected to find mostly firn (porous, partially compacted snow) with thin, patchy ice layers or “lenses” scattered within.

MacFerrin and his colleagues wondered if the ice layers became thick enough to block surface meltwater, how long might it take for meltwater to pool at the surface and run off toward the coast? … Landsat 7 satellite images showed unprecedented lakes and rivers forming and draining westward. Meltwater poured into the Watson River 90 miles away, contributing to the worst flooding on record ...

continuous, thick ice lenses extend dozens of miles further inland than ever recorded before and cover more than 27,000 square miles, the approximate size of New Jersey, New Hampshire and Vermont combined. [emphasis mine]

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