In southeast Alaska, “glacier change is continuing with no pause or slowdown apparent in the data,” said Chris Larsen.
Larsen would know. Since 2009, the glaciologist from the University of Alaska, Fairbanks, has been making two sets of flights over the region’s glaciers each year for NASA’s Operation IceBridge mission. From the air, Larsen and colleagues have collected critical information on how the region’s snow and ice are changing.
“Many glaciers have changed so much that I find it hard to remember what they looked like even 10 years ago,” Larsen said. Fortunately, the changes are documented in the data. “We see 75 billion tons of ice lost each year, an amount that is impossible to put on humanly comprehensible scales.”
Measurements from the mission have also shown large variability in how individual glaciers are responding to climate. Larsen notes that for some glaciers—such as Columbia and Yakutat—the changes are profound. For others, such as the Johns Hopkins Glacier pictured above, the changes are more subtle.
Larsen shot the photo from the De Havilland Otter aircraft on May 27, 2020. Johns Hopkins is one of more than 1,000 glaciers located within the boundaries of Glacier Bay National Park and Preserve. Most of the park’s glaciers are found inland, high in the mountains. In contrast, Johns Hopkins Glacier flows eastward for miles from the Fairweather Range and down into the waters of Johns Hopkins Inlet in Glacier Bay.
Johns Hopkins and other glaciers that end in seawater—so-called tidewater glaciers—primarily lose mass through the calving of icebergs. Larsen and colleagues previously showed that as a group, tidewater glaciers are relatively stable and not losing as much mass as land- or lake-terminating glaciers. (There are exceptions, such as the rapid retreat and mass loss at Columbia Glacier).
The front, or terminus, of Johns Hopkins Glacier has even been shown to be advancing in recent years, moving farther out into the fjord. IceBridge measurements made from 2014 and 2017 showed thickening across the glacier’s upper reaches and thinning across some of its lower reaches. As a whole, the glacier appears to be gaining more ice than it is losing.
“It will be interesting to see this campaign’s data,” Larsen said, “This kind of glacier can be pretty variable from year to year.”
Operation IceBridge has flown over the Arctic, Antarctica, and Alaska since 2009, collecting data designed to bridge the decade-long gap in observations between NASA’s ICESat and ICESat-2 satellites. Following the launch of ICESat-2 in 2018, IceBridge made its final polar flight in November 2019; the final set of IceBridge-Alaska flights take place this summer.
Operation IceBridge photo by Chris Larsen, University of Alaska, Fairbanks. Story by Kathryn Hansen.