University of Alaska Fairbanks    |    Scenarios Network for Alaska + Arctic Planning

Thawing Index

The thawing index, or degree days above freezing, is a measure of thawing that occurs during a year. It is also a measure of summer duration and temperatures.

Choose a location below by community name, coordinates, or by clicking on the map to select a point.

  • ✓  Modeled Historical (1980–2009, ERA Interim)
  • Projected Mid–Century (2040–2069, NCAR CCSM4, RCP 8.5)

Thawing index

These layers show the historical or projected thawing index across Alaska.

Degree days above 32°F
≥ 5000

The thawing index is the annual cumulative degree days (°F) above freezing for each location. These degree days are calculated by taking the number of degrees above 32°F for each day of the year and adding them together into a single value. A higher thawing index means a warmer year for that location.

Areas with thawing indexes much less than their freezing indexes are candidates for at least some permafrost. Areas with small thawing indexes and large freezing indexes tend to have continuous permafrost.

Larger values indicate warmer temperatures. Increases in thawing index over time suggest warmer and longer summers, increased active layer depth, and a decrease in ice and snow.