Glaciers in the Americas Are Melting Faster

Glaciers in the snowy mountains of western Canada are melting faster than they were a decade ago, according to scientists.

New research suggests that ice loss in the southern Coast Mountains of British Columbia is happening at nearly five times the rate it was in the early 2000s.

Overall, glaciers in western North America—not including Alaska—have lost about 117 billion tons of ice since 2000; they are currently losing about 12 billion tons a year.

The vast ice sheets of Greenland and Antarctica get the most global attention when it comes to melting glaciers, largely because of their immense potential to contribute to sea-level rise. Greenland is currently the biggest loser, pouring nearly 300 billion tons of ice into the ocean each year, by recent estimates. But Antarctica is a rising concern—research published this week finds that the Antarctic ice sheet is losing about 250 billion tons of ice annually, and the melt rate seems to be accelerating (Climatewire, Jan. 15).

Still, Greenland and Antarctica aren’t the only important frozen places on Earth. Glaciers exist in many regions, from the Americas to the Swiss Alps to the Himalayas. Scientists are finding that many of these glaciers are also melting and retreating, likely in response to rising temperatures.

And while most of them aren’t likely to make much of a dent in global sea-level rise—in part because many mountain glaciers don’t empty into the oceans—these losses are still important. Many are a critical source of fresh water, helping to feed the streams and rivers that wildlife and human communities depend on.

As the glaciers shrink, experts worry that these water supplies could begin to dry up. So keeping close tabs on melt rates, and the factors that influence them, can help communities plan for the future.

This week, two studies took a closer look at glaciers in North and South America. The first, published in the journal Geophysical Research Letters, focuses on the mountains of western North America—excluding Alaska, where many studies have already been conducted, but including glaciers in British Columbia and the U.S. Pacific Northwest.

Taken as a whole, satellite imagery suggests, the region has been losing substantially more ice from 2009 to the present—about four times as much—than in the previous decade. That’s mainly because of the high losses in Canada’s Coast Mountains, which are home to a majority of western North America’s glaciers. Farther south in the Pacific Northwest, however, the researchers actually found that some places were seeing less intensive melt rates now than in the previous decade.

The reasons for the differences may be linked to a shift in atmospheric patterns and weather conditions, the scientists suggest. In the latter decade, the researchers noted a change in the position of the jetstream, a major air current in the Northern Hemisphere.

This shift brought changes in wind patterns over western Canada and the Pacific Northwest, as well as changes in regional temperatures and precipitation patterns. Some areas, particularly those farther south, became wetter, while other areas farther north became warmer and drier and began to melt faster. The researchers suggest that these changes, on top of the background warming caused by greenhouse gas emissions, may help account for the significantly higher melt rates in parts of Canada in the past decade.

“I think there would need to be more work done on whether this positional change in the jetstream is natural variability or caused by [anthropogenic] climate change,” said lead study author Brian Menounos of the University of Northern British Columbia.

That said, the researchers suggest that future climate change could make some of these effects worse.

Previous modeling studies suggested that severe climate change might continue to alter wind patterns over the mountains of western North America, causing some winds to become weaker. It’s similar to the changes the researchers observed over the last decade, which they believe contributed to the accelerated ice loss in Canada. That’s on top of the baseline increases in melting expected to occur as temperatures continue to rise.

Meanwhile, a second study published this week in Nature Climate Change confirmed that Patagonia, a region that includes parts of southern Chile and Argentina, is losing more ice than any other area in South America. The new estimates, also based on satellite imagery, suggest that the northern and southern Patagonian ice fields—covering about 6,500 square miles, the largest expanse of ice in the Southern Hemisphere besides Antarctica—are losing around 17 billion tons of ice each year.

Altogether, the study suggests glaciers in South America are losing about 20 billion tons of ice annually. The new estimates anticipate lower rates of ice loss in some parts of the continent than previous studies, particularly around the tropics, but more or less agree with the high melt rates observed in Patagonia.

As the new study points out, air temperatures in that region of the world are on the rise, contributing to “enhanced melt conditions,” although the Patagonian ice fields seem to be responding more strongly than other glaciers in the general area.

Previous research has also suggested that ice loss in Patagonia may be accelerating in recent years and that glaciers there may be retreating at some of the fastest rates in the world. Unlike mountain glaciers found in more inland regions of the world, its melting ice can run off into the ocean and have some effect on sea-level rise. Right now, the melting may be contributing around one-twentieth of a millimeter of sea-level rise each year, or around 2 percent of the current rate of global sea-level rise.

As temperatures continue to rise around the world, glaciers in North and South America aren’t the only ones at risk. Scientists have documented shrinking ice on every continent, frequently in places where human communities rely on them for water.

Continued monitoring is critical to helping these communities understand and prepare for the changes that are already happening—and for helping them make predictions about the future, Menounos noted.

“One of the keys to improving models to forecast the future fate of glaciers depends quite heavily on having good observational data to validate how these models behave—in much the same way that a global climate model is evaluated on how well it does to predict the trend of temperature or precipitation in a given decade,” he said in an interview. “So observations are absolutely essential.”

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.



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