Permafrost dynamics modeling in Alaska using a high spatial resolution dataset

Climate projections for the 21st century indicate that there could be a pronounced warming and degradation of permafrost in the Arctic and sub-Arctic regions. SNAP is working with UAF geophysicists to map projected permafrost statewide.

Thawing and freezing of soils is affected by many factors, with air temperature, vegetation, snow accumulation, and soil moisture among the most significant. Recent observations indicate a warming of permafrost in many northern and mountain regions with a resulting degradation of ice-rich and carbon-rich permafrost.

Permafrost temperature has increased by 1–2°C in northern Russia during the last 30 to 35 years. This observed increase is very similar to what has been observed in Alaska, where warming is typically from 0.5–2°C. In the last 30 years, warming in permafrost temperatures observed in the Russian North and Alaska has resulted in the thawing of natural, undisturbed permafrost in areas close to the southern boundary of the permafrost zone. 

What we did

To assess possible changes in the permafrost thermal state and active layer thickness, the GIPL-1.3 model was implemented for the entire Alaskan permafrost domain.

For this study we used an input data set with 2 x 2 km spatial resolution. Input parameters to the model are:

  • spatial data sets of mean monthly air temperature and precipitation
  • prescribed vegetation
  • soil thermal properties
  • water content

Parameters are specific for each vegetation and soil class and geographical location.

Climate forcing and SNAP data.  The SNAP data set was used to model climate forcing. SNAP data were derived from the five IPCC Global Circulation Models that perform the best in Alaska: ECHAM5, GFDL21, MIROC, HAD and CCCMA. These were selected based on how closely model outputs matched climate station data for temperature, precipitation, and sea level pressure for the recent past.

Downscaling.  The outputs from these five models have been downscaled to 2 km resolution using the PRISM model, which accounts for elevation, slope, and aspect. Each derived value represents a single month within a given year, based on the composite (mean) output of the five models, using the A1B emission scenario. 

Ground temperatures at the depth of the active layer for twelve decades from 1980-2100 were also calculated.

What we found

Results of the simulation show that by the end of the 21st century, the mean annual ground temperatures (MAGT) at the bottom of the active layer could be above 0°C within the vast territory south of 68° latitude North except for the high altitudes of the Alaska Range and the Wrangell Mountains.

At the same time, results show how different types of ecosystems affect the stability and thermal state of permafrost. While in the northern part of the Brooks Range areas of permafrost degradation have appeared by the end of simulation period, some patches of stable permafrost still could survive in interior Alaska.

Areas of expertise: 
Scenario planning
Data visualization and analysis
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