New research finds that “unusual changes in atmospheric jet stream circulation caused the exceptional surface melt of the Greenland Ice Sheet (GrIS) in summer 2012.”
Prof. Jennifer Francis tells me these changes are consistent with those caused by warming-driven “Arctic Amplification.” And that means GrIS may melt faster than climate models have projected.

Extent of surface melt over Greenland’s ice sheet on July 8, 2012 (left) and July 12, 2012. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed. Credit: NASA.

Back in May, a study found that by 2025, there is a “50-50 chance” of this unprecedented ice melt happening annually simply based on the continued rapid warming of GrIS.

This new study, “Atmospheric and oceanic climate forcing of the exceptional Greenland ice sheet surface melt in summer 2012,” suggests this kind of melt may become commonplace even sooner.

As the news release explains, an international team used a computer model and satellite data “to confirm a record surface melting of the GrIS for at least the last 50 years – when on 11 July 2012, more than 90 percent of the ice-sheet surface melted. This far exceeded the previous surface melt extent record of 52 percent in 2010.” Weather station data “showed that several new high Greenland temperature records were set in summer 2012.”

The research “clearly demonstrates that the record surface melting of the GrIS was mainly caused by highly unusual atmospheric circulation and jet stream changes, which were also responsible for last summer’s unusually wet weather in England.”

What were these changes? Professor Edward Hanna from the University of Sheffield’s Department of Geography explains:

Read more

By Michael D. Lemonick via Climate Central

When 97 percent of Greenland’s ice experienced at least some melting in July 2012, scientists wondered if it was a one-time phenomenon. Now a new study in Geophysical Research Letters indicates it is a sign of things to come and by 2025, there is a 50-50 chance of it happening annually.

Extent of surface melt over Greenland’s ice sheet on July 8, 2012 (left) and July 12, 2012. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed. Credit: NASA.

It’s not clear what the effects of such melting will be: the majority of Greenland’s ice loss, which has accelerated significantly over the past decade, comes from glaciers shedding more ice into the sea, and moving faster toward the sea, not from melting snow and ice at higher elevations of the ice sheet.

Nevertheless, such widespread melting indicates an overall warming in the region that could threaten the ice more generally, adding significantly to the threat of sea level rise.

The 2025 projection is based on two factors, according to lead author Dan McGrath, a glaciologist at the University of Colorado, Boulder. The first is a series of temperature measurements going back to 1950 at the Summit research station, at the highest — and on average, the coldest — point on the Greenland ice sheet. The mercury has been rising more or less steadily there for that entire time, with the fastest increase, of about .22° F per year, coming since 1992. “That’s six times faster than the global average,” McGrath said in an interview.

The highest parts of the ice sheet still remain below the freezing mark virtually all the time, but when unusual weather conditions set in — an especially warm air mass, or as in the case of the 2012 melting, an influx of clouds just thin enough to let sunlight through but thick enough to block heat from escaping — the thermometer can sneak above 32°F. “Only an hour above freezing is enough to start the surface melting,” McGrath said.

Another factor that went into the analysis involved what’s known as the equilibrium line — the altitude where the snow is neither piling up year to year nor shrinking. Over the past 20 years or so, that transition zone has been gradually moving up the ice sheet by about 115 feet every year, on average— another indication that temperatures on the frozen island are warming.

Read more

You can help crowd-fund an important scientific research trip — along with a videographer and journalist to cover it. Climate De-Crocker Peter Sinclair explains:

On April 21, 2013, the Dark Snow Project brought a bit of Greenland to Manhattan, to illustrate the importance of this summer’s planned expedition to sample Greenland ice. It kicked off the last leg of our historic citizen-science crowd funding campaign.

If this final fundraising push is successful, I’ll be traveling in June to the Greenland Ice sheet as part of a scientific expedition to investigate the steady darkening and increasing melt of that important ice sheet. Bill Mckibben will be coming along to write this up for Rolling Stone, as well.

Here is a video on the Dark Snow Project:

They are almost half-way to their $150,000 target. Let’s see if Climate Progress readers can take them over $100,000. Here’s how:

One, you can go to Darksnowproject.org, and make a donation at the bottom of the page. Two, you can text darksnow to 50555.

At a dinner I attended last night, glaciologist Jason Box explained why he believes Greenland’s disintegration is likely to keep outpacing Antarctica’s for the foreseeable future. He has a detailed explanation at his blog, Meltfactor, reposted below. See also Chris Mooney’s interview of Box here and “Greenland Ice Melt Up Nearly Five-Fold Since Mid-1990s“ – JR.

Changes in global sea level due to ice sheet melting since 1992. Credit: ESA/NASA/Planetary Visions via NBC.

Icy contenders weigh in

by Jason Box, Ph.D.

Dahl-Jensen et al. (2013)^[i] suggest that the Greenland ice sheet was more stable than previously thought^[ii], enduring ~6k years of temperatures 5-8 C above the most recent 1000 years during the Eemian interglacial 118-126k years before present, its loss at the time contributing an estimated 2 m (6.6 ft) of global sea level compared to a total of 4-8 m (13-26 ft)^[iii], implying Antarctica was and will become the dominant source of sea level change. Consequently, environmental journalist Andrew Revkin writes: “The dramatic surface melting [in Greenland], while important to track and understand has little policy significance.”

Given the non-trivial complexity of the issue and that Greenland has been contributing more than 2:1 that of Antarctica to global sea level in the recent 19 years (1992-2010)^[iv], let’s not consider Greenland of neglible policy relevance until that ratio is 1:1 if not reversed, say, 0.5:1. Greenland, currently the leading contender with surface melting dominating its mass budget^[v], the positive feedback with surface melting and ice reflectivity doubling Greenland’s surface melt since year 2000^[vi]. Professor Richard Alley weighs in again: “We have high confidence that warming will shrink Greenland, by enough to matter a lot to coastal planners.”

That’s not to say that Antarctica couldn’t take over from Greenland the position of number 1 global sea level contributor in the foreseeable future. Nor should one be surprised if it did, given that Antarctica contains a factor of 10 more ice than Greenland^[vii],[viii].  And it is probable that the planetary energy imbalance^[ix] caused by elevated greenhouse gasses, expressed primarily through massive oceanic heat uptake^[x], is delivering enough erosive power to destabilize the 3.3 m of sea level^[xi] in the marine-based West Antarctic ice sheet. Yet, for today, consider also that climate change if increasing Antarctic precipitation a few percent can tip its mass balance toward the positive, lessening its sea level contribution^[xii] even while its glaciers retreat.

Irrespective of sea level forcing, through its ice mass budget Greenland plays an important role to North Atlantic climate through ocean thermohaline circulation, even being suggested as the Achilles heel of the global climate system^[xiii]. I wouldn’t tell our European friends Greenland’s hardly policy-relevant when climate change offers higher amplitude extremes in precipitation if not also temperature, as North Atlantic climate shifts in partial response to changes in neighboring Greenland.

Key differences between the modern Anthropocene and the Eemian interglacial suggest anthropogenic climate change may drive a different cryosphere response than during the Eemian…

Read more

NASA reported today some truly shocking findings on the melting of the Greenland ice sheet this summer:

Satellites See Unprecedented Greenland Ice Sheet Surface Melt

July 24, 2012: For several days this month, Greenland’s surface ice cover melted over a larger area than at any time in more than 30 years of satellite observations. Nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its two-mile-thick center, experienced some degree of melting at its surface, according to measurements from three independent satellites analyzed by NASA and university scientists.

On average in the summer, about half of the surface of Greenland’s ice sheet naturally melts. At high elevations, most of that melt water quickly refreezes in place. Near the coast, some of the melt water is retained by the ice sheet and the rest is lost to the ocean. But this year the extent of ice melting at or near the surface jumped dramatically. According to satellite data, an estimated 97 percent of the ice sheet surface thawed at some point in mid-July.

Extent of surface melt over Greenland’s ice sheet on July 8 (left) and July 12 (right). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12.

We reported last month on the “Unprecedented May Heat In Greenland,” where the temperature hit 76.6°F. So it would seem that unprecedented heat leads to unprecedented melting.

I saw the ABC News story tonight, which had the headline quote. I’ll post the video when it is online.

The NASA release has more detail:

Son Nghiem of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., was analyzing radar data from the Indian Space Research Organisation’s (ISRO) Oceansat-2 satellite last week when he noticed that most of Greenland appeared to have undergone surface melting on July 12. Nghiem said, “This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?”

Nghiem consulted with Dorothy Hall at NASA’s Goddard Space Flight Center in Greenbelt, Md. Hall studies the surface temperature of Greenland using the Moderate-resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites. She confirmed that MODIS showed unusually high temperatures and that melt was extensive over the ice sheet surface.

Thomas Mote, a climatologist at the University of Georgia, Athens, Ga; and Marco Tedesco of City University of New York also confirmed the melt seen by Oceansat-2 and MODIS with passive-microwave satellite data from the Special Sensor Microwave Imager/Sounder on a U.S. Air Force meteorological satellite.

The melting spread quickly. Melt maps derived from the three satellites showed that on July 8, about 40 percent of the ice sheet’s surface had melted. By July 12, 97 percent had melted.

This extreme melt event coincided with an unusually strong ridge of warm air, or a heat dome, over Greenland. The ridge was one of a series that has dominated Greenland’s weather since the end of May. “Each successive ridge has been stronger than the previous one,” said Mote. This latest heat dome started to move over Greenland on July 8, and then parked itself over the ice sheet about three days later. By July 16, it had begun to dissipate.

Even the area around Summit Station in central Greenland, which at 2 miles above sea level is near the highest point of the ice sheet, showed signs of melting. Such pronounced melting at Summit and across the ice sheet has not occurred since 1889, according to ice cores. . . .

“Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” says Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data. “But if we continue to observe melting events like this in upcoming years, it will be worrisome.”

That statement is a classic example of what James Hansen called “scientific reticence.”

The scientific literature and recent observations — along with our ongoing lack of climate action — have long passed the worrisome stage (see the post last month “Greenland Ice Sheet Melt Nearing Critical ‘Tipping Point’ ” and links below).

Neven’s Arctic Sea Ice blog notes that “In the meantime Dr. Jason Box reports on the Meltfactor blog“:

Read more

JR: Last year, scientists explained that the Greenland Ice Sheet “could undergo a self-amplifying cycle of melting and warming“ that is “difficult to halt.” A new study finds we may be close to a “tipping point.” Climate Central has the story.

Satellite data of Greenland reflectivity June 1-22, 2012 versus the same periods in previous Junes back to 2000. The blue colors indicate a decrease in reflectivity compared to previous Junes. Credit: NASA/Meltfactor.org.

by Andrew Freedman, via Climate Central

The Greenland ice sheet is poised for another record melt this year, and is approaching a “tipping point” into a new and more dangerous melt regime in which the summer melt area covers the entire land mass, according to new findings from polar researchers.

The ice sheet is the focus of scientific research because its fate has huge implications for global sea levels, which are already rising as ice sheets melt and the ocean warms, exposing coastal locations to greater damage from storm surge-related flooding.

Greenland’s ice has been melting faster than many scientists expected just a decade ago, spurred by warming sea and land temperatures, changing weather patterns, and other factors. Until now, though, most of the focus has been on ice sheet dynamics — how quickly Greenland’s glaciers are flowing into the sea. But the new research raises a different basis for concern.

The new findings show that the reflectivity of the Greenland ice sheet, particularly the high-elevation areas where snow typically accumulates year-round, have reached a record low since records began in 2000. This indicates that the ice sheet is absorbing more energy than normal, potentially leading to another record melt year — just two years after the 2010 record melt season.

“In this condition, the ice sheet will continue to absorb more solar energy in a self-reinforcing feedback loop that amplifies the effect of warming,” wrote Ohio State polar researcher Jason Box on the meltfactor.org blog. Greenland is the world’s largest island, and it holds 680,000 cubic miles of ice. If all of this ice were to melt — which, luckily won’t happen anytime soon — the oceans would rise by more than 20 feet.

In a new study, Box and a team of researchers describe the decline in ice sheet reflectivity and the reasons behind it, noting that if current trends continue, the area of ice that melts during the summer season is likely to expand to cover all of Greenland for the first time in the observational record, rather than just the lower elevations at the edges of the continent, as is the case today. The study has been accept for publication in the open access journal The Cryosphere. Read more

Figure 1. Difference between the number of melt days in 2011 and the average number of melt days during the period 1979 – 2010. Large sections of the island experienced twenty more days with melting conditions than average. Image: Arctic Report Card.

by Jeff Masters, via the WunderBlog

The record books for Greenland’s climate were re-written [last] Tuesday, when the mercury hit 24.8°C (76.6°F) at Narsarsuaq, Greenland, on the southern coast. According to weather records researcher Maximiliano Herrera, this is the hottest temperature on record in Greenland for May, and is just 0.7°C (1.3°F) below the hottest temperature ever measured in Greenland. The previous May record was 22.4°C (72.3°F) at Kangerlussuaq (called Sondre Stormfjord in Danish) on May 31, 1991. The 25.2°C at Narsarsuaq on June 22, 1957 is the only June temperature measured in Greenland warmer than yesterday’s 24.8°C reading. Wunderground’s extremes page shows that the all-time warmest temperature record for Greenland is 25.5°C (77.9°F) set on July 26, 1990.

The exceptional warmth this week was caused by the combination of an intense ridge of high pressure and a local foehn wind, said the Danish Meteorological Institute. The unusual May heat has extended to Scotland, which had its hottest May temperature on record on May 25 at Achnagart: 29.3°C (85°F). Greenland’s Narsarsuaq has seen a string of 3 consecutive days over 70°F this week–the 3rd, 7th, and 12th warmest days there since record keeping began in 1941. The ridge of high pressure responsible is expected to stay in place several more days, bringing additional 70° days over Southern Greenland. The warm May temperatures could be setting the stage for a big Greenland melt season this summer–the International Research Institute for Climate and Society (IRI) is predicting a 50 – 60% that the southern 2/3 of Greenland will experience above-average temperatures this summer. They forecast just a 10 – 15% chance of below-average temperatures.

Why Greenland is important

If the massive icecap on Greenland were to melt, global sea level would rise 7 meters (23 ft).

Read more

Ohio State News Release

The 2010 Uplift Anomaly (green arrows), superimposed on a map showing the 2010 Melting Day Anomaly (shaded in red). Click to Enlarge.

An unusually hot melting season in 2010 accelerated ice loss in southern Greenland by 100 billion tons – and large portions of the island’s bedrock rose an additional quarter of an inch in response.

That’s the finding from a network of nearly 50 GPS stations planted along the Greenland coast to measure the bedrock’s natural response to the ever-diminishing weight of ice above it.

Every year as the Greenland Ice Sheet melts, the rocky coast rises, explained Michael Bevis, Ohio Eminent Scholar in Geodynamics and professor in the School of Earth Sciences at Ohio State University.  Some GPS stations around Greenland routinely detect uplift of 15 mm (0.59 inches) or more, year after year. But a temperature spike in 2010 lifted the bedrock a detectably higher amount over a short five-month period – as high as 20 mm (0.79 inches) in some locations.

In a presentation Friday at the American Geophysical Union meeting in San Francisco, Bevis described the study’s implications for climate change.

“Pulses of extra melting and uplift imply that we’ll experience pulses of extra sea level rise,” he said. “The process is not really a steady process.”

Because the solid earth is elastic, Bevis and his team can use the natural flexure of the Greenland bedrock to measure the weight of the ice sheet, just like the compression of a spring in a bathroom scale measures the weight of the person standing on it.

Read more

Greenland Ice Sheet Ties Record for Mass Loss in 2011

Another day, another amplifying feedback or vicious cycle.

The Greenland ice sheet can experience extreme melting even when temperatures don’t hit record highs, according to a new analysis by Dr. Marco Tedesco, assistant professor in the Department of Earth and Atmospheric Sciences at The City College of New York.  His findings suggest that glaciers could undergo a self-amplifying cycle of melting and warming that would be difficult to halt.

“We are finding that even if you don’t have record-breaking highs, as long as warm temperatures persist you can get record-breaking melting because of positive feedback mechanisms,” said Professor Tedesco, who directs CCNY’s Cryospheric Processes Laboratory….

… melting in 2011 was the third most extensive since 1979, lagging behind only 2010 and 2007. The “mass balance”, or amount of snow gained minus the snow and ice that melted away, ended up tying last year’s record values.

The photo on the right is “Marco Tedesco standing on the edge of one of four moulins (drainage holes) he and his team found at the bottom of a supraglacial lake during the expedition to Greenland in the summer, 2011.”

It’s not news that there are amplifying feedbacks at work on the great ice sheets.  Just this March, the U.S. Jet Propulsion Laboratory published its analysis that Polar ice sheet mass loss is speeding up, on pace for 1 foot sea level rise by 2050.  That study found:

The Greenland and Antarctic ice sheets are losing mass at an accelerating pace, according to a new NASA-funded satellite study. The findings of the study — the longest to date of changes in polar ice sheet mass — suggest these ice sheets are overtaking ice loss from Earth’s mountain glaciers and ice caps to become the dominant contributor to global sea level rise, much sooner than model forecasts have predicted.

But the new CCNY study, based on in situ observations “during a four-week expedition to the Jakobshavn Isbræ glacier in western Greenland,” lays out for the first time a very specific amplifying feedback occurring way up north:

CLICK HERE TO READ MORE OR COMMENT

Read more