NASA’s Earth Science News Team
What is permafrost?
Larry Hinzman
Permafrost is soil, rock, or peat that has been frozen below zero degrees Celsius (32 degrees Fahrenheit) continuously for two or more years. This means it’s not defined by geology or region. It can exist in high mountain areas such as the Rocky Mountains and Africa’s Mt. Kilimanjaro; in peak elevations, such as in North and South Dakota; and even in rare spots on the Hawaiian Islands. Permafrost is like frozen chicken in that it thaws but it does not melt (in contrast to ice which melts).
NASA
How did you find yourself studying frozen soil?
Larry Hinzman
Following a childhood in rural South Dakota, I pursued a degree in agronomy. Agronomy explores the impact of agriculture on the environment and melds the biology, chemistry, and earth science associated with soil with meteorology and plant growth. After completing that master’s degree, I came to Alaska on a vacation. I loved it so much up here that I got a job working for a gold prospector, but nearly starved that winter without finding much gold. A friend recommended a job at the university in Fairbanks as an agricultural field technician, which was more aligned with my education.
Despite fighting off attacks to our experiments from buffalo and sandhill cranes, I enjoyed the work and decided to pursue a doctorate in soil physics.
I leapt from agronomy to hydrology, but the two are linked. So much of the study of water in agriculture involves understanding how permafrost controls moisture in Alaskan soils, and therefore whether some crops grow and others don’t when permafrost is present.
NASA
How does thawing permafrost affect life in Alaska and elsewhere in the Arctic?
Larry Hinzman
In Alaska, we’re living right on the knife’s edge between frozen and thawed landscape. That’s a huge difference between the lower 48 states and us. Temperature changes here affect the structural stability of entire ecosystems much more than in a more temperate state such as Arkansas.
If permafrost changes — if it degrades even a foot — it will act like a big domino that knocks everything else over. When the sun’s rays hit frozen soil, the soil moisture evaporates, making the surface cooler. Without permafrost, drier soil causes surface warming, and this changes the local climate. Thawing permafrost also releases methane into the atmosphere in amounts potentially far greater than human emissions.
Permafrost below the Arctic Ocean has trapped huge quantities of methane (called gas hydrates), and as the permafrost degrades, the amount of escaping methane increases, with implications for climate change.
NASA
What tools do you use to detect and measure permafrost?
Larry Hinzman
Permafrost is very hard to see. But we can trace changes in surface conditions that sometimes occur when permafrost thaws with a technique called interferometry, which uses electromagnetic waves to point us to places where surface subsidence has occurred. Interferometry allows us to detect massive surface disturbances called “thermokarsts,” which are produced as permafrost thaws and ice wedges contained in it melt.
We also use NASA’s gravity-detecting GRACE satellites, which help us trace changes in groundwater reservoirs that may indicate thawing permafrost.
NASA
How are NASA and the University of Alaska involved in the study of permafrost?
Larry Hinzman
We have an ongoing satellite project with NASA to look at Russian permafrost. Russia is experiencing rapid degradation of permafrost, and we want to learn more about how that thawing is affecting the levels of lakes and rivers and the amount of melt water — released from melted snow or ice — pouring into the ocean.
The Russians have been collecting runoff data for a century. Those data are telling us that runoff is increasing in the winter, but we’re trying to figure out why. We believe that thawing permafrost plays a role in controlling infiltration of rain and snowmelt, which affects the timing of eventual runoff into rivers and to the ocean. We know for sure that the increased runoff is contributing to a freshening of the waters of the Arctic Ocean; lower-density freshwater tends to float on the saltier ocean water. Increases in fresh water near the Earth’s poles could affect the circulation in the oceans, which influences everything from atmospheric temperatures to storm intensity.
NASA Earth Observatory story by Gretchen Cook-Anderson
