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Addressing the Impacts of Climate Change on U.S. Army Alaska with Decision Support Tools Developed through Field Work and Modeling
Dr. Thomas Douglas | U.S. Army ERDC-CRREL
The U.S. Army is the largest Department of Defense (DoD) land user in Alaska, overseeing
1.5 million acres of training range and cantonment lands. Some of the training ranges are inaccessible by road. Infrastructure planned over the next 10 years to address access issues will greatly expand the DoD’s presence and capabilities in Alaska. The training ranges and cantonments are underlain by a complex mosaic of discontinuous permafrost and its presence (or absence) plays a major role in soil thermal, hydrologic, and vegetation regimes.
A projected 1 to 3 ºC increase in mean annual air temperatures in the area between now and 2100 is expected to have major ramifications on ecosystem and hydrologic processes and their potential feedbacks to climate-permafrost-ecologic interactions. This project was conducted to identify the potential impacts of climate warming on U.S. Army Alaska training lands and to provide land managers with scientifically based information to help them plan for a warmer future. Results were linked with a broad array of historical and projected meteorological and climatological information to develop a geospatial decision support system to help DoD manage its lands in a potentially warmer future.
This project included a variety of field measurements and the application of multiple modeling platforms to identify how, where, and at what rate climate warming could impact vegetation, soils, hydrology, and permafrost on interior Alaska DoD lands. Repeat imagery was synthesized with field measurements of vegetation, soil, geomorphic, geophysical, and hydrologic information.
The University of Alaska Fairbanks Geophysical Institute Permafrost Laboratory (GIPL) soil and vegetation thermal model also was coupled to the U.S. Army Corps of Engineers Gridded Surface Subsurface Hydrologic Analysis (GSSHA) hydrogeologic model. The resulting software package was tested with measurements from a research watershed near Fairbanks to validate the ability to simulate streamflow in watersheds with a variety of permafrost coverage. This product will allow for the projection of how and where stream flows may change when permafrost extent is modified by press climate change processes or by pulse disturbances.
The project results were synthesized with the most up to date climate projections for Alaska and ecosystem information on soils, hydrology, permafrost extent, fire history, and vegetation to develop a queriable geographic information systems decision support tool that has been delivered to U.S. Army Alaska training range managers. This support tool is called the Geographic Information Supporting Military Operations (GISMO).
The project addressed five thematic areas:
- Research focused on permafrosthydrogeology relationships on the Tanana Flats lowlands. To support this, an array of wells were installed across a lake-fen system to understand the seasonality of surface and shallow subsurface hydrologic flow. Regionally, surface water and groundwater move northward from the Alaska Range across the training ranges to feed an extensive (i.e., hundreds of square kilometers) wetland system. Permafrost plays a major role in channeling flow across this landscape. With a projected warmer climate and degradation of near surface permafrost it is likely that the lateral connectivity of flow paths will increase and flows across these fen systems will be reduced. Enhanced downward movement of flow paths will lead to an overall drying of the landscape. This will alter ecosystem processes and feed back to hydrogeology and water use. The downward movement of surface waters and their warm thermal mass will also promote permafrost thaw.
- Research assessed the vulnerability of permafrost to fire-initiated thaw on training ranges. Five fire scars were identified across a chronosequence from 1930 to 2010 that were investigated for the rate and patterns of permafrost and vegetation response to fire. Thermal modeling was used to better evaluate the relative effects of burn severity on the soil thermal regime. We also attempted to identify when vegetation succession and redevelopment of the ecosystem protection of permafrost would return to these terrains.
- Research quantified how and where biophysical, geophysical, and airborne measurements could be used to map subsurface permafrost geomorphology. Electrical resistivity tomography (ERT) was determined to be a robust tool in mapping three dimensional permafrost features to depths of tens of meters. Strong relationships were detected between vegetation type, topography measured with differential global positioning system (dGPS) and light detection and ranging (LiDAR) measurements, and permafrost extent. These relationships indicate that remote sensing of vegetation characteristics and LiDAR could be useful for monitoring the surficial and seasonal thaw depth response of permafrost to fire, human disturbance, or climate warming.
- The modeling effort focused on combining two established modeling capabilities- one that simulates the soil thermal regime and freeze-thaw processes and the other a surface shallow subsurface hydrological tool- into a coupled permafrost hydrology model. Two teams worked to synchronize the models and permafrost soil and hydrology measurements from a long term study site were used to tune and apply the model to real world measurements. The model adequately reproduced real world hydrologic information and was able to account for the varied flow responses to precipitation events in watersheds underlain by different amounts of permafrost.
This project used repeat imagery analyses of landscape change to identify ecosystem transitions across the landscape. Fire history and biophysical factors affecting ecosystem change were measured through photo-interpretation of 2000 systematically distributed points on a time-series (1949−1952, 1978−1980, 2006−2011) of geo-rectified imagery across interior Alaska Army training lands. Overall, 56.8% of the region had changes in ecotypes over the 55−62 year period and most of the changes resulted from increases in upland and lowland forest types with an accompanying decrease in upland and lowland scrub types, as post-fire succession led to late-successional stages.
The results from this study will help to identify how, where, and hopefully when ecological changes will occur in interior Alaska ecosystems. Our study sites are on the front lines of projected climate warming and impacts on ecosystems due to Arctic amplification. The primary benefit of this study for the DoD is scientifically based strategic installation planning capabilities that account for potential climate change impacts on training ranges. U.S. Army Alaska received a queriable web based geospatial decision support tool that provides a soil thermal modeling capability, a module to project future permafrost extent, historical and projected meteorologic information for all seasons, and a fire history database. For the U.S. Army Corps of Engineers, the GSSHA hydrologic model can now account for seasonal freeze thaw processes and can be applied to permafrost and seasonally frozen terrains. The thermal and hydrologic model results are transferable to other locations such as Afghanistan, Korea and the northern conterminous United States.
The scientific community will benefit through new and novel data presented in peer reviewed publications and Technical Reports. These results include field measurements and modeling applications focused on mapping permafrost bodies, modeling hydrologic flow, predicting the soil thermal response to climate warming, understanding post fire disturbance effects on permafrost, and tracking ecosystem transitions over time.