Thawing Permafrost in Alaska: What the USGS Is Learning and Why It Matters

Shoreline erosion near Drew Point on Alaska's north coast. Ben Jones, USGS.

Why the USGS studies it

The U.S. Geological Survey, with university, federal, Tribal and independent partners, researches where permafrost is, how vulnerable it is and why it matters in arctic and boreal ecosystems.

• Scientists, land managers and policymakers use the data in decisions on development, wildlife habitat and more.
• Native villages and cities can forecast landscape change and where soils may thaw with more confidence.
• Researchers use it to build scenarios of future permafrost change.

What permafrost does

Permafrost is frozen ground under about a quarter of the Northern Hemisphere, and it shapes the Arctic's landscape and how it works:

• Water: it holds surface water in place instead of letting it drain away, which shapes where plants and animals live.
• Ground: it keeps soils structurally sound enough to build houses and roads on.
• Stability: ecosystems on stable permafrost may resist disturbances such as wildfire and erosion.

When it thaws

Continued warming is expected to thaw permafrost across large regions this century.

• Surface water and groundwater move differently, making some places wetter and others drier.
• Erosion and landslides can speed up, and the ground can sink.
• Permafrost holds huge amounts of soil organic matter, frozen for tens of thousands of years. Thawed, microbes break it down — releasing greenhouse gases, reducing soil carbon, and changing soil nutrients and water quality.

The top meter of soil: the active layer over dark permafrost, gray to black from its organic content and lack of oxygen. J. O'Donnell, National Park Service.

A record of past ice ages

Permafrost records how sediment, plant remains and ice built up over time. From cores of permafrost, wetland soils and lake sediments — dating plant tissue and minerals — USGS researchers work out when permafrost formed and thawed in the past, improving the picture of climate history.

• Some of the oldest permafrost formed in the Pleistocene, as much as 700,000 years ago.
• Elsewhere it formed only in the last few thousand years (the late Holocene), as high latitudes cooled.
• Permafrost soils are often rich in carbon and ice, so thaw matters for greenhouse gases and for where water goes. Knowing the history helps build sturdier scenarios of what climate change will do.

Watching it change

Change is measured with air- and space-borne imagery, geophysics, deep borehole temperature probes and monitoring of the active layer — the surface soil that thaws and refreezes each year.

• Coastlines: from historical maps, aerial and satellite photos and elevation data, USGS scientists track how Alaska's coast has changed since the 1940s. There is both erosion and build-up, but in places the coast has retreated as much as 22 meters (~72 feet) a year. Thawing permafrost, along with sea-ice loss, speeds erosion, with serious consequences for coastal communities.

Rates of coastal erosion in Alaska from field surveys and remote sensing. Permafrost thaw can speed erosion to more than 5 meters (16 feet) a year. Base from a USGS 300-meter digital elevation model. USGS.

• Lakes: lakes formed by thawing permafrost — thermokarst lakes — are a signature of Alaska. Over thousands of years they grow from small thaw pits into bigger lakes, and many eventually drain. In the Yukon Flats, a sub-Arctic river lowland, about 1 in 10 lakes shrank between the 1980s and 2014, before heavy rain and snow from 2015 refilled them. Statewide, national wildlife refuges lost 0.8 percent of their lake area a year before 2015.
• Seeing underground: geophysics can probe permafrost without drilling — like an x-ray instead of surgery. Airborne electromagnetic (AEM) surveys from aircraft map permafrost and soil more than 100 meters (>300 feet) deep over large, remote areas. In the Yukon Flats, AEM mapped permafrost around lakes, ponds and rivers: under water that doesn't freeze solid in winter, the ground stays unfrozen and can link surface water with deeper groundwater — possibly part of why lakes shrink and grow. Ground-based methods then track change in more detail.

Geophysics at different scales: (A) airborne electromagnetic surveys, (B) nuclear magnetic resonance, (C) electrical resistivity tomography, (D) ambient seismic tomography and (E) time-domain electromagnetic measurements. Burke Minsley (A–D) and David Rey (E), USGS.

Why long-term fieldwork matters

Many of the processes behind thaw and landscape change show up only over years to decades, so the USGS keeps long-term monitoring sites across Alaska.

• Carbon and nutrients: changes in permafrost change how carbon and nutrients move into forests, wetlands, lakes and rivers. Thawed permafrost carbon often escapes as greenhouse gas, adding to the buildup in the atmosphere.
• New tools: drone-mounted gas sensors, laser spectrometers and geophysical instruments show thaw and gas release in finer detail; macrofossils, pollen and environmental DNA reveal past plant and microbe communities and how frozen microbes cycle carbon and nutrients.
• What gets released: water moves more easily through thawed soil, so carbon, nutrients, microbes and contaminants frozen for thousands of years reach the environment and surface waters, and move up food webs. Mercury, a neurotoxin, concentrates in permafrost: the USGS estimates Northern Hemisphere permafrost holds twice as much as non-permafrost soils, the atmosphere and the oceans combined — a serious risk to health and food supplies.

Drilling permafrost cores to measure carbon storage and other properties. K. Wickland, USGS.

A core is cut into sections by hand in the field before going to the lab. Jennifer Harden, USGS.

Wildlife and plants

Thaw changes the size and spread of lakes and ponds, helping some species and hurting others — and fast enough to strain predictions and management.

• The shores of shrinking lakes quickly fill with rich wetland plants — which later may flood again.
• Northern lakes and wetlands are key breeding grounds for waterfowl, so shifting water changes local biodiversity.
• On Alaska's arctic coastal plain, thaw has let salt water flood in and salt marsh grow — good goose habitat, feeding a growing population of snow geese.
• Wildlife shape permafrost too: in parts of the Arctic, beavers have created thermokarst lakes and ponds.

Working with Indigenous communities

USGS scientists monitor permafrost with Tribal environmental professionals in Alaska Native villages, Canadian First Nations and Indigenous nonprofits, in community-based research. Interviews bring local and Indigenous knowledge of landscape change into the science; ground collapse, changing lakes and water supply, wildfire behavior, and plant and animal resources have all been documented. The USGS shares results through community reports, talks and online resources.

Tribal environmental professionals from the Indigenous Observation Network work with USGS researchers to track permafrost thaw and water quality. Nicole Herman-Mercer, USGS.

The USGS centers involved: the Geology, Minerals, Energy, and Geophysics Science Center; the Florence Bascom Geoscience Center; the Earth Resources Observation and Science Center; the Water Mission Area; the Geology, Geophysics, and Geochemistry Science Center; the Alaska Science Center; the Pacific Coastal and Marine Science Center; and the Geoscience and Environmental Change Science Center.

Sources

Based on USGS Permafrost Research Determines the Risks of Permafrost Thaw to Biologic and Hydrologic Resources, USGS Fact Sheet 2020–3058, U.S. Geological Survey; a work of the United States government in the public domain. Photographs and the coastal erosion map are taken from the fact sheet's PDF; its permafrost and lake maps, drawn on commercial base maps and imagery, are not reproduced.