Climate Change on U.S. Arctic Ocean Margins

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By Coastal and Marine Hazards and Resources Program June 17, 2019

Arctic Alaska is warming faster than the rest of the United States. A major consequence of this warming is permafrost thaw, which threatens infrastructure, alters habitat, increases fire risk, changes nutrient and sediment delivery to the coastal ocean, and enhances greenhouse gas release. The warming climate has already dramatically reduced the thickness and annual duration of sea ice, rendering the Arctic U.S. Exclusive Economic Zone more accessible to other nations’ vessels and the coastlines more vulnerable to erosion from wave action. Coastal bluffs, which serve as polar bear nurseries and as protection for some Native settlements, and low relief barrier islands and coastal plains, which are the site of most energy production infrastructure, are susceptible to the impacts of increased storm intensity and sea level rise, additional consequences of a warming climate. Identifying and quantifying these effects are made particularly challenging by the Arctic’s remote location and harsh climate.

Shoreline is crumbling into the water, and the land itself is interlocking polygons with brackish water in the centers. — This photograph shows ice-wedge polygons and an eroding shoreline at Cape Halkett on the Beaufort Sea coast of Alaska. Coastal erosion along the Arctic coast is chronic, widespread, and potentially accelerating, posing threats to infrastructure important for defense and energy purposes, natural shoreline habitats, and nearby Native communities. To help address these concerns, the USGS is collecting information on past and present shoreline changes along the conterminous United States and parts of Alaska and Hawaii. Credit: Bruce Richmond/Ann Gibbs, USGS

Satellite view of land surrounded by sea with a box around an area of coastline and another box around the area of study. — Map of Alaska, with the white box outlining Arctic Alaska and its coastline. The red box shows the location of Barter Island. Basemap from Google Maps.

CMHRP scientists lead regional-scale studies that measure and model the impact of climate change across the land-ocean interface at the edge of the Arctic Ocean in northern Alaska. Using laser-based methods and photography, several USGS projects, including Climate Impacts to Arctic Coasts, Coastal National Elevation Database (CoNED), and CMHRP’s National Assessment of Shoreline Change, have mapped coastal landforms at high resolution and documented landscape changes due to permafrost degradation and coastal erosion taking place over months to decades.

High coastal arctic bluff with broken chunks, some that are ready to fall into the crashing waves, and some that have fallen. — USGS is studying climate change impacts to U.S. Pacific and Arctic coasts. Alaska’s north coast is predominantly erosional, retreating on average about 1.4 meters per year. Certain stretches, like this one on Barter Island, are experiencing much higher erosional rates, some upwards of 5-15 meters per year. Credit: Bruce Richmond, USGS

Four views from the sky of the same area of shoreline from different years to show how the land is eroding through time. — Aerial imagery of tundra and ocean showing the impacts of coastal erosion near Drew Point, Alaska. Between 1955 and 2009, approximately 7,000 acres of land were washed into the sea along a 40-mile (64-kilometer) stretch of Beaufort Sea coastline that included the portions shown here. The annual rates of coastline erosion were 20, 27, and 55 feet (6, 8, and 17 meters) per year, respectively, for the periods 1955 to 1979, 1979 to 2002, and 2002 to 2009. For year-to year reference, note the large lake near the center of the photo. The colored lines in the 2009 image outline the location of the shoreline in the years indicated. Credit: Benjamin M. Jones, USGS

To more accurately evaluate the impact of accepted global warming scenarios on the Alaskan Arctic coastline over the next century, CMHRP ocean-atmosphere models take into account field measurements of sea level, salinity, water and sediment temperature, and sediment characteristics near areas currently being inundated by rising seas. The models predict periods of increased flooding in low-lying areas in the coming decades and highlight the vulnerability of barrier islands to storm surges.

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Barter Island, Alaska, lies at the northern edge of the Arctic National Wildlife Refuge on the Arctic Ocean coastline. Permafrost bluffs in this area are eroding rapidly as climate warms, storm intensity increases, and permafrost thaws. The CMHRP investigates many aspects of this changing landscape, from radon in groundwater to sediment transport along the coast. » See the Video

CMHRP scientists have also tracked methane dynamics in thermokarst lakes on the Alaskan North Slope and reconstructed climate changes over the past 20,000 years since the end of the last major glaciation. Offshore, CMHRP researchers have measured emissions of methane and carbon dioxide, two important greenhouse gases, imaged nearly ubiquitous shallow gas in seafloor sediments there, and mapped the distribution of gas hydrates. The CMHRP has also mapped the seaward extent of subsea permafrost along the entire Arctic Ocean coastline of northern Alaska. The subsea permafrost persists only to about 20 km offshore, implying rapid thawing of permafrost under the inundated shelf since the end of the last major glaciation.