A new satellite-based study of the retreating permafrost coastline at Drew Point, in Alaska’s North Slope region, shows that from 1955 to 1979, the rate of loss was only about 23 feet per year. From 2007 through 2016, it was about 56 feet per year.
“I’ve basically been watching that coastline erode and collapse for a little more than a decade now,” said Benjamin Jones of the University of Alaska at Fairbanks, who has been studying the Drew Point site since 2007. Jones is lead author of a new study, aided by 25 colleagues from a host of institutions in the United States and Germany, documenting a decade’s worth of changes at this site located between Utqiaġvik (previously Barrow), the northernmost U.S. city, and Prudhoe Bay.
The study at Drew Point, where shallow waters offshore are fronted by 16-foot bluffs, is showing especially fast rates of erosion and may hint that much of the coastline encircling the Arctic could be undergoing similar, if not quite as rapid, changes — even if they are unknown and unrecorded.
Jones provided The Washington Post with daily camera images showing a typical spring-to-summer progression at the site, from late April through early September of this year. In the images, you can watch as the landscape thaws, the sea ice clears, and then the bluffs start collapsing into the sea — in this case, dragging along with them a data logger and buoy that the scientists had installed to take readings.
“That small buoy, when it did fall into the ocean, it was able to maintain float, and I was able to retrieve it,” Jones said.
It’s not the first such time-lapse video taken at Drew Point, a site that makes such a presentation almost irresistible — but it comes as the new research affirmed a speedup of losses over the past decade.
Jones and his colleagues, in their new study in Environmental Research Letters, calculate that the coast, on average, is retreating inland by 56 feet per year, or just less than 20 yards. That’s 2.5 times the prior measured rates.
In the most extreme year, 2016, the coast retreated by an average of 72 feet. Most strikingly, all of this is occurring during a relatively narrow window of roughly 90 days, or the open-water season, when the coast is beset by waves. The length of the open-water season has also doubled in recent decades.
Calculating the consequences over a 5½-mile stretch of coastline, Jones said means that about 30 football fields are being lost annually and that about 300 were lost in total between 2007 and 2016.
Few other stretches of Arctic coastline are being watched in the same way. Jones estimates that only 1 to 2 percent of Arctic coastlines have been surveyed to study how much they are eroding, and few to the extent that Drew Point has been.
Yet vulnerable permafrost — the reason for what’s happening at Drew Point — is present across the Arctic.
The bluffs at Drew Point are composed of a mixture of frozen soil and thick wedges of ice. They are very sensitive to temperature — and both the air and the sea alike in this location have been getting warmer.
Perhaps more important, though, is that with the retreat of Arctic sea ice, the period of open water offshore, when waves can break free from winter ice, is getting longer. This allows waves to slam into the coast, the most immediate trigger of the loss of land.
“Bringing the level of the sea up to the base of the bluff eats away at the base of the ice-rich permafrost, eroding it both thermally and mechanically,” Jones said.
Nobody lives at Drew Point, but the loss of sea ice, and the resulting increase in waves, has been a threat to a number of Arctic communities. That includes tiny Kivalina, on the coast of the Chukchi Sea, which is seeking to relocate because waves threaten the barrier island where the community sits.
The Drew Point site presents an interesting contrast with another place in the United States that is also losing land rapidly — but for very different reasons. That’s the Louisiana Gulf Coast, where wetland loss rates of late have amounted to a football field every 100 minutes.
But there are massive differences, notes Torbjorn Tornqvist, a coastal geologist at Tulane University who studies the region.
The Louisiana coast has been studied for more than half a century, Tornqvist explained, and the causes of change include sea-level rise, land subsidence, dams and other obstructions that sap sediment from the Mississippi River, destruction of wetlands for canals, oil and gas projects, and more.
In contrast, much of the Alaska coastline has no infrastructure, and rising seas are not really the big issue — it’s all about warming and the retreat of ice, followed by the punishing waves.
“A system like this is potentially even more sensitive to climate change, compared to lower-latitude coasts like Louisiana,” Tornqvist said. “It strikes me that just temperature change alone can be a huge factor here due to the destabilizing effect of thawing permafrost. Put differently, even without sea-level rise, coastlines like these might exhibit accelerated rates of retreat.”