Accelerating coastal retreat in Alaska: The triple threat

The combined effects of sea level rise, permafrost thaw subsidence, and coastal retreat threaten to reshape Arctic coastal regions on an unprecedented scale, surpassing the impact of any single climate hazard. 

According to scientists, this compounding set of factors will lead to drastic land loss, posing significant challenges for Arctic communities.

Overlapping hazards magnify coastal retreat 

While decades of research have documented the growing threat of coastal erosion in the Arctic, the additional roles of sea level rise and permafrost thaw subsidence have been less explored. 

This gap in understanding has limited the ability to evaluate the full extent of these combined processes and their impacts on Arctic landscapes.

A new study by researchers from the Woods Hole Oceanographic Institution (WHOI) and other institutions, focuses on the Alaska Arctic Coastal Plain (ACP). Spanning more than 60,000 square kilometers, this low-lying, ice-rich region experiences some of the Arctic’s most extreme rates of erosion and sea-level rise.

“Our findings highlight the risks that compounding climate hazards pose to coastal communities and underscore the need for adaptive planning for Arctic communities within zones of 21st-century land loss,” the experts wrote.

A stark forecast for Arctic shorelines

The study presents a stark forecast for the North Slope shoreline, predicting a dramatic inland retreat by 2100 due to the interplay of these three hazards.

“Compound climate impacts accelerate coastal change,” said lead author Roger Creel, a postdoctoral scholar in WHOI’s Department of Physical Oceanography. “There is this nonlinear acceleration in coastal impacts that we should be expecting will happen in places like Northern Alaska.”

The shoreline is expected to retreat farther inland than it has been in over 100,000 years, during the last interglacial period. 

“By 2100, the combined effects of coastal erosion, sea level rise, and permafrost thaw subsidence will likely push the North Slope shoreline inland to a location it hasn’t reached since the last interglacial period over 100,000 years ago,” explained co-author Benjamin Jones of the University of Alaska Fairbanks.

Projections of coastal retreat 

The researchers utilized advanced tools to assess future land loss, including 5-meter topography, satellite-derived lake depth measurements, and empirical data on permafrost thaw subsidence. 

The team incorporated these with projections of coastal erosion and sea level rise under medium- and high-emission scenarios from the IPCC’s 6th Assessment Report.

“This research highlights the value of working across disciplinary boundaries for more robust projections of coastal Arctic evolution in the coming century,” said co-author Julia Guimond, an assistant scientist at WHOI. 

“Our work shows that by 2100, total land loss will exceed erosional losses by up to eight times. Here we focus on processes affecting Alaska’s Arctic Coastal Plain, but a key takeaway is the compounding effects of multiple hazards and that applies to coastal resilience planning across the globe.”

Permafrost thaw: A hidden dominator

The study emphasizes that permafrost thaw subsidence will be the dominant factor driving land loss, surpassing even sea level rise and coastal erosion in its long-term impacts.

“Along ice-rich permafrost coastlines, the land surface is falling faster than the sea levels are rising,” noted co-author Pier Paul Overduin from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research. 

“Over the coming decades, permafrost thaw subsidence will move the coastline farther inland than coastal erosion or sea level rise alone will move it, and this subsidence will dominate Arctic coastal change over the long term.”

Creel highlighted the need for greater awareness among decision-making agencies, such as the U.S. Army Corps of Engineers and FEMA, to allocate resources more effectively. 

“These sorts of bodies with a lot of resources may have not been paying enough attention to permafrost thaw subsidence as an agent of coastal change. This study is a wake-up call to expand the conversation.”

Communities on the frontline of change

An Arctic coastline shaped by inundation will create unprecedented challenges for the communities that call this region home. These include the loss of infrastructure, hunting grounds, subsistence routes, and cultural heritage sites.

“Future research on Arctic shoreline evolution should be motivated by the needs of these communities, who will need support to respond to the paradigm shift in 21st-century Arctic coastal change that we project here,” the authors concluded.

The study is published in Proceedings of the National Academy of Sciences.

Image Credit: Photo by: Benjamin M. Jones, Institute of Northern Engineering, University of Alaska Fairbanks

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–