Jeff Masters: The Heat is On in Greenland
June 30, 2014
Dr. Jeff Masters has a nice write up or current Greenland conditions, and the Dark Snow Project. He mentions Maniitsoq, which is one of the stops we made last year on our way to the ice cap, and the site one month later of the warmest temps in Greenland’s historical record. See Above.
The graph Dr. Masters uses reminded me of a similar one from James Hansen, which I’ve inserted below the fold, along with ominous results of recently published research. The message is, we’d better get Greenland right.
Dr. Jeff Masters at Weather Underground:
The heat is on in Greenland, where the high temperature on Tuesday hit an unusually warm 67°F at Kangerlussuaq (Sønder Strømfjord) in southwestern Greenland. It’s been a hot June at Kangerlussuaq, where the temperature peaked at 73°F on June 15. That’s not far below the all-time hottest temperature ever recorded in Greenland of 78.6°F, set just last year on July 30 at nearby Maniitsoq Mittarfia, as documented at wunderground’s extremes page. The unusual warmth this year melted nearly 40% of the Greenland Ice Sheet in mid-June, according to data from the National Snow and Ice Data Center–far above the usual 15% figure. The warm June temperatures could be setting the stage for a big Greenland melt season this summer, and scientists with the Dark Snow Project are on the ice, 48 miles east Kangerlussuaq, conducting a two-month field experiment on the causes and implications of Greenland ice melt.
Human-caused global warming has set in motion an unstoppable slow-motion collapse of the glaciers in West Antarctica capable of raising global sea level by 4 feet (1.2 meters) in a few hundred years, said NASA in a May 2014 press release. What’s more, one of the glaciers involved, the Thwaites Glacier, acts as a linchpin on the rest of the ice sheet, which contains enough ice to cause a total of 10 to 13 feet (3 to 4 meters) of global sea level rise over a period of centuries. This unstoppable collapse makes saving Greenland “absolutely essential”, said glaciologist Richard Alley in a May 2014 interview in Mother Jones.
Greenland’s ice sheet holds enough water to raise global sea levels by 7.36 meters (24.15 feet) were it all to melt, and civilization would be hard-pressed to deal with 10 – 13 feet of sea level rise from West Antarctica, let alone another 20+ feet from Greenland. “If we’ve committed to 3.3 meters (10.8′) from West Antarctica, we haven’t committed to losing Greenland, we haven’t committed to losing most of East Antarctica,” said Alley. “Those are still out there for us. And if anything, this new news just makes our decisions more important, and more powerful.” Unfortunately, the Greenland Ice Sheet is much more vulnerable to melting than previously thought, found a May 2014 study by Morlighem et al.,Deeply incised submarine glacial valleys beneath the Greenland ice sheet. The researchers found that widespread ice-covered valleys extend much deeper below sea level and farther inland than previously thought, and would likely melt significantly from steadily warming waters lapping at Greenland’s shores.
Fig. 1 shows that Greenland has been losing mass at a faster and faster rate over the past decade, with the recent rate corresponding to ~1 mm sea level per year (1 mm sea level = 360 Gt ice). The linear fit to the Shepherd et al. data in Fig. 1 yields a Greenland contribution to global sea level of about 30 cm by 2100.
The increasing Greenland mass loss in Fig. 1 can be fit just as well by exponentially increasing annual mass loss, a behavior that Hansen (2005, 2007) argues could occur because of multiple amplifying feedbacks as an ice sheet begins to disintegrate. A 10-year doubling time would lead to 1 meter sea level rise by 2067 and 5 meters by 2090. The dates are 2045 and 2057 for 5-year doubling time and 2055 and 2071 for a 7-year doubling time.
However, exponential ice loss, if it occurs, would encounter negative (diminishing) feedbacks. Our simulations (Hansen and Sato, 2012) suggest that a strong negative feedback kicks in when sea level rise reaches meter-scale, as the ice-melt has a large cooling and freshening effect on the regional ocean. Such a slowdown in the rate of sea level rise would be little consolation to humanity, however, as the high latitude cooling would increase latitudinal temperature gradients, thus driving powerful cyclonic storms (Hansen, 2009), and coastlines would be continually moving landward for centuries.
Meanwhile, new research of Greenland’s past suggests the ice sheet is more sensitive than previously thought.
A new study suggests that a warming period more than 400,000 years ago pushed the Greenland ice sheet past its stability threshold, resulting in a nearly complete deglaciation of southern Greenland and raising global sea levels some 4-6 meters.
The study is one of the first to zero in on how the vast Greenland ice sheet responded to warmer temperatures during that period, which were caused by changes in the Earth’s orbit around the sun.
Results of the study, which was funded by the National Science Foundation, are being published this week in the journal Nature.
“The climate 400,000 years ago was not that much different than what we see today, or at least what is predicted for the end of the century,” said Anders Carlson, an associate professor at Oregon State University and co-author on the study. “The forcing was different, but what is important is that the region crossed the threshold allowing the southern portion of the ice sheet to all but disappear.
“This may give us a better sense of what may happen in the future as temperatures continue rising,” Carlson added.
The researchers’ analysis of the scope of the ice loss suggests that deglaciation in southern Greenland 400,000 years ago would have accounted for at least four meters – and possibly up to six meters – of global sea level rise. Other studies have shown, however, that sea levels during that period were at least six meters above present, and may have been as much as 13 meters higher.
Carlson said the ice sheet loss likely went beyond the southern edges of Greenland, though not all the way to the center, which has not been ice-free for at least one million years.
In their Nature article, the researchers contrasted the events of Marine Isotope Stage 11 with another warming period that occurred about 125,000 years ago and resulted in a sea level rise of 5-10 meters. Their analysis of the sediment record suggests that not as much of the Greenland ice sheet was lost – in fact, only enough to contribute to a sea level rise of less than 2.5 meters.
“However, other studies have shown that Antarctica may have been unstable at the time and melting there may have made up the difference,” Carlson pointed out.
Support the Dark Snow Project
One of Dr. Box’s collaborators, photographer James Balog, who created the amazing time-lapse Greenland glacier footage in the fantastic 2012 “Chasing Ice” movie, puts it like this: “Working in Greenland these past years has left me with a profound feeling of being in the middle of a decisive historic moment–the kind of moment, at least in geologic terms, that marks the grand tidal changes of history.” On that note, I encourage you all to consider a tax-deductible donation to the Dark Snow Project. The project has already raised $30,000, and hopes to raise another $10,000. One of the major uses for the money will be to pay for the portable Internet satellite gear needed to do regular posting, messaging, and skyping from the ice during July and August.