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
Does melting of the East Antarctic Ice Sheet (EAIS) pose a threat to sea level rise? Studies of the ice melt that fuels sea level rise often focus on the prominent warming and melting of glaciers in Greenland and western Antarctica. The massive East Antarctic Ice Sheet (EAIS) has been largely ignored, until recently. “It’s generally been assumed that it’s so big and so cold that it’s probably immune to some of the warming trends we’ve seen across the planet,” said Chris Stokes, a professor at Durham University. Two recent studies, however, paint a new picture of the world’s thickest, unwavering giant, suggesting the need to look deeper into eastern Antarctica.
Sensitivity to climate
Using 50 years of observed flight and satellite data of 175 glaciers along 5,400 kilometers (3355 miles) of coastline, Stokes and his team of researchers concluded that the EAIS is more sensitive to climate shifts than suspected. The results showed the glaciers rapidly responding to minor temperature shifts. For every degree increase, the glaciers retreated 0.5 kilometers (0.3 miles) per decade. “We detected a clear synchronization between what the glaciers were doing and what the climate was doing,” he said. The analysis found three trends: 63 percent of glaciers retreated from 1974 to 1990, when it was warmer; 72 percent advanced from 1990 to 2000, when it was cooler; and 58 percent advanced from 2000 to 2010, a period that experienced phases of warming and cooling.
At its highest, the EAIS is almost 5 kilometers (3 miles) thick, containing about 50 meters (164 feet) of sea level equivalent. Stokes is careful to point out, however, that this amount wouldn’t be dumped into the ocean in any short amount of time, and if it were to happen, it would probably take thousands of years. “The implication with our study,” said Stokes, “is that if we keep adding greenhouse gases into the atmosphere, we could expect to see changes similar to those taking place in Greenland and west Antarctica.”
A peak into the past
Another study suggest that the EAIS has melted once before, during the Pliocene Epoch some 5 to 2.5 million years ago, a period that is comparable in atmospheric CO2 concentrations and global temperatures to those predicted for the end of this century. The EAIS alone added about 10 meters (33 feet) to sea level rise. “This is already after a completely deglaciated West Antarctic Ice Sheet and deglaciated Greenland Ice Sheet,” said Carys Cook, a researcher at Imperial College London. “In total that accounts to be 22 meters (72 feet) of global sea level rise.”
To study this long-ago event, Cook and her team of researchers focused on the Wilkes Subglacial Basin, a large low-lying region where the ice sheet is up to 2.4 kilometers (1.5 miles) below sea level. Glacier systems below sea level are some of the fastest accelerating of the world. “If any retreat was to take place in the EAIS,” Cook said, “this would be the site.”
They analyzed marine sediment cores drilled off shore near East Antarctica and about 2.9 kilometers (1.8 miles) below sea level. The presence of a specific type of rock, only present in large quantities quite far and deep within the Wilkes Subglacial Basin, indicated serious ice sheet retreat. “Since most ice sheet erosion occurs at the margin of the ice sheet, that indicated times when the ice sheet retreated,” Cook said. Increasingly warming seawater sloshed exposed rocks about 161 kilometers (100 miles) inland of the current ice sheet edge.
Cook states that the next piece of the puzzle is to quantify the rate of change for these events. “If something similar happens today,” she said, “we really need to get a nail on how quickly it will happen.”
Stokes added, “We hope studies like these will help persuade other scientists to investigate glaciers in East Antarctica.”
Cook, Carys P. et al. 2013. Dynamic behaviour of the East Antarctic ice sheet during Pliocene warmth. Nature Geoscience 6, 765-769, doi:10.1038/ngeo1889.
Miles, B. W. J., C. R. Stokes, A. Vieli, and N. J. Cox. 2013. Rapid, climate-driven changes in outlet glaciers on the Pacific coast of East Antarctica. Nature 500, 563-566, doi:10.1038/nature12382.
Have you been skiing in the Western U.S. and been surprised by brown snow? We recently talked to a research team that studies these coats of dirt. The dust storms that cause dusty snow appear to be getting bigger, thanks to climate warming drying out this region. Worse, dust on snow may increase flooding and slowly smother water supplies in the southwestern U.S. How bad is this situation and who will be affected by it? Can anything be done?
The what and where of dust
The more dust, the darker the surface and the faster snow will melt, because dark surfaces absorb more solar energy. “Sunlight is the major snow melter,” said Jeff Deems, a research scientist at NSIDC. “It’s not air temperature.” Fresh snow reflects anywhere between 90 to 95 percent of solar energy. “Very dusty snow, on the other hand, may reflect as little as 30 percent, meaning 70 percent is absorbed,” Deems said. If you more than double absorbency, you’re dramatically increasing the rate at which snow melts.
Dust storms boil out of the arid regions of the West. Jason Neff, a professor of Geology and Environmental Studies at the University of Colorado Boulder, said, “We know humans have increased dust by disturbing desert soils: grazing animals, driving vehicles, building roads and towns.” With the settlement of the West, post 1860s, dust has increased. “It wasn’t completely dust free before,” Deems said, “but by the mid to late 1800s the dust levels jumped up seven-fold.”
Is the extreme the new norm?
In recent years, increased temperature and prolonged drought have been drying the West. 2009, 2010, and now 2013 saw some very large dust storms. “There is indication from our colleagues out in the desert that the extreme scenarios could be a more frequent occurrence,” Deems said.
The extreme dust masses witnessed in 2009 and 2010 absorbed two to four times the solar radiation, and shifted peak snowmelt four to seven weeks earlier, compared to before the West was settled. Timing is everything. Scientists estimate that earlier soil exposure can decrease annual runoff by about 5 percent. Exposed land evaporates more water. Earlier snowmelt also triggers an earlier growing season, allowing for vegetation to take up and evaporate water. “Nothing can be done about the loss of water to evapotranspiration,” said Thomas Painter, a research scientist at the NASA Jet Propulsion Laboratory. “It’s permanent.”
The Colorado River brings water to more than 40 million people in cities like Denver, Las Vegas, Phoenix, and Los Angeles, punctuated by dams that store its water in reservoirs. Lakes Powell and Mead combined can store about four years worth of Colorado River flow, but for the Upper Colorado Basin, snowpack is the most important reservoir. “We can store way more water as snow in the mountains than we can in our reservoirs—vastly more,” Deems said. “So the longer the snow sticks around, the longer we have water. If flow comes early, then we’re stuck in late summer with only what could be stored in surface water reservoirs.”
Faster snowmelt also suggests a surge in river flow, and when rivers come up faster, water management gets complicated. “It’s just like if you turn on your sink, and if you only have a 101 gallons of water potential and your faucet blasts a hundred gallons out before you even get a cup underneath, then the person behind you in line may only fill their cup half full,” Painter said.
Climate models project that by 2050 the Colorado River will lose 5 to 20 percent of its total runoff. “It’s not good,” said Painter. “To put a dent in the flow like that—people are going to feel it.” The river irrigates 5.5 million acres of agriculture. But something can still be done. If the amount of dust blown onto Colorado River snowpacks can be reduced, a more stable snow pack lingers, giving way to a trickling river system rather than a roaring, untamable beast. Painter added, “By reducing dust loading, we may stem some climate change tide in terms of water loss.”
Deems, J. S., T. H. Painter, J. J. Barsugli, J. Belnap, and B. Udall. Combined impacts of current and future dust deposition and regional warming on Colorado River Basin snow dynamics and hydrology. 2013. Hydrology and Earth System Sciences Discussion 10, 6237-6275, doi:10.5194/hessd-10-6237-2013.
Painter, Thomas H., J. S. Deems, J. Belnap, A. F. Hamlet, C. C. Landry, and B. Udall. Response of Colorado River runoff to dust radiative forcing in snow. 2010. Proceedings of the National Academy of Sciences, doi:10.1073/pnas.0913139107.
Most people picture the Arctic Ocean as miles upon miles of thick sea ice. This icy expanse has become threatened as Arctic sea ice shifts from mainly old ice to much younger, thinner ice. How does this shift impact the Arctic environment? And what is the connection between the average age of ice found in the Arctic and the overall sea ice decline? Continue reading
After a cool Arctic summer, sea ice at the North Pole has recovered somewhat from last year’s record low extent. While this is a welcome pause in the downward trend of sea ice extent, some are taking it a step further and hailing this rebound as evidence that the Arctic is no longer warming. But does the recent uptick mean that we have entered a period of global cooling? NSIDC scientists point out why we shouldn’t be reading too much into one summer of less sea ice decline. Continue reading