Although Arctic sea ice extent did not set a low record this year, it’s still clear that there is less sea ice than there used to be. Scientists are keeping a close eye not only on the dwindling ice, but also on the ripple effect its loss might have on the rest of the Arctic environment. A big question involves the exchange of heat between ocean and air—and the weather patterns that result. What does current research say about how floating ice—or the lack of it—might be changing the Arctic atmosphere? Continue reading
The Big One
The Great Arctic Cyclone of 2012 lifted out of Siberia on August 2nd, swirling in a counter-clockwise rotation up into the Arctic. As one of the most extreme Arctic cyclones ever recorded, its consumption of an already low sea ice extent raised many concerns. Now Arctic cyclones are garnering attention, but is all the hype warranted?
“People seem to have this thought that all this storminess is unusual,” said Mark Serreze, an Arctic climatologist and center director at NSIDC. “Well it’s not. It simply isn’t. Summer is the time for cyclones.” Arctic summers are not calm. In fact, the months of August and September see a maximum amount of cyclonic activity. Not every summer is very stormy, but overall, the Arctic is the Arctic for a reason. Continue reading
In spite of the massive blizzards that have slammed parts of the northeastern United States, much of the country is experiencing a pronounced lack of snow. And where there is snow, it is less than usual. It follows a very low snow year from the previous season, causing people to worry if low snowfall is the new normal.
A previous Icelights post, Arctic sea ice and U.S. weather, discussed possible causes behind the changes in winter weather, trying to see if there are correlations to larger climate changes. Researchers like Jennifer Francis of Rutgers University are exploring the possibility that declining sea ice in the Arctic is altering atmospheric temperatures and weakening the jet stream. This change may shift the Northern Hemisphere storm track, leaving some places unusually snowy, or leaving normally snowy locations dry. Can a few good blizzards help reverse the snow drought across parts of the United States? Or is this string of dry winters yet another symptom of climate change? Continue reading
During the summer of 2012, scientists noticed something unusual in Greenland. On July 8, about 40 percent of the Greenland Ice Sheet surface showed signs of melting. But a mere four days later, 97 percent of the surface was melting, an extent that was unprecedented in the satellite record.
Just how unprecedented was this event? Does it mean that the Greenland Ice Sheet is possibly on the way out, like summer sea ice in the Arctic?
The Greenland block
To be clear, the Greenland Ice Sheet is still very much intact. It will take much more than a warm summer to melt ice that covers 660,000 square miles and averages 1.43 miles in thickness. And surface melt is quite shallow, including only the top several centimeters, according to Thomas Mote, a professor at the University of Georgia. Mote is one of many scientists studying Greenland’s ice, investigating what caused such a dramatic melt. Mote credits last summer’s extreme melt in large part to a weather pattern called the Greenland block. “Greenland blocking is a persistent high pressure ridging over Greenland,” Mote said. “That is when we will see warmer than normal conditions and more melt.” During a normal summer, about half of the ice sheet surface experiences melt. Last summer, this high-pressure block essentially parked over Greenland, creating a lasting dome of heat that rapidly melted nearly the entire ice sheet surface.
Melting in context
Much of the media coverage cited a historical precedent for the melt, focusing on an ice core record from Summit Station, Greenland. This core indicated that such extreme melts are not unusual, and have occurred as frequently as every 150 years. But records from a single location, while invaluable, may oversimplify the history of such a vast ice sheet, and may not account for more recent changes in the broader environment surrounding Greenland.
“You’re talking about a single event at Summit that is quite remarkable but very short-lived, versus this sort of broad warming and increase in melt over much of Greenland,” Mote said. “The increased melt that we’ve seen in Greenland over the past several years is associated with the general warming across the Arctic.” Greenland experienced record warming in 1999, 2007, 2010, and in 2012, mirroring years in which the Arctic as a whole experienced warming, and often, record sea ice minimums.
Mote and others hope to place the extreme event into a larger environmental context, seeing how factors like air temperatures and winter accumulation might play a role. And in spite of the recent warming, Mote cites some positive evidence among the many questions that Arctic warming often raises. “There is some evidence recently that suggests that the Greenland Ice Sheet can recover more easily perhaps than we might have thought,” Mote said. “I think we’re still trying to get a sense of just how inter-related these different cryospheric measures are across the Arctic.”
Nghiem, S. V., D. K. Hall, T. L. Mote, M. Tedesco, M. R. Albert, K. Keegan, C. A. Shuman, N. E. DiGirolamo, and G. Neumann. 2012. The extreme melt across the Greenland ice sheet in 2012. Geophysical Research Letters, 39, L20502, doi:10.1029/2012GL053611.
A reader recently asked if the date of the annual Arctic sea ice minimum is shifting later each year. And if so, is that shift a sign of heat being stored in the Arctic region?
According to the satellite record, Arctic sea ice generally melts to its minimum annual extent between the first and third week of September, after which ice begins freezing again. In recent decades, the Arctic has been gaining heat: Air, land, and ocean temperatures in the region have been slowly rising, and scientists have noted dramatic reductions in summer sea ice extent, as this heat causes more ice to melt away. But is this heat causing sea ice to form later each fall? Continue reading