Remotely-Sensed Active Layer Thickness (ReSALT) Product Derived from InSAR Data over North American Arctic Region

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Kevin Schaefer

Project Summary

Project Summary Study of the active layer and permafrost is one of the four science themes of the planned NASA-sponsored field campaign of the Arctic-Boreal Vulnerability Experiment (ABoVE). Data and information on the active layer and near-surface permafrost conditions are crucial for better understanding of the terrestrial ecosystem dynamics, surface hydrologic and landscape processes, and human infrastructure in the Arctic. The International Permafrost Association's Circumarctic Active Layer Monitoring (CALM) program has conducted site-specific and grid (1 kilometer by 1 kilometer) measurements over the past two decades and has produced valuable data and information. However, the existing CALM network is still under-populated and does not represent the full range of climatic and physiographic variability, making them poorly suited for the planning the NASA ABoVE project. Satellite remote sensing using the Interferometric Synthetic Aperture Radar (InSAR) technique can provide data and information on regional-scale active layer thickness and permafrost ground-ice conditions across a broad climatic and physiographic spectrum.

The goal of this project is to expand the Remotely-Sensed Active Layer Thickness (ReSALT) data set from a small region near Prudhoe Bay, Alaska, to the entire North American Arctic regions across the proposed ABoVE domain. The ReSALT data over the Prudhoe Bay, Alaska, agree well with CALM measurements with an uncertainty level of 10 centimeters.

Specifically, we will (a) optimize the InSAR Frozen Ground Algorithm (InSAR FGA) for speed and accuracy, (b) generate ReSALT products derived from the InSAR FGA from circa 1991-2014 across the proposed study areas.

The expected data products are: (a) multi-year average ReSALT, (b) time series of active layer thickness (ALT) change; and (c) ground-ice addition or melting in the top layers of permafrost.

The generated ReSALT data products will essentially cover the majority of the continuous permafrost regions in North America and have a spatial resolution varying from tens of meters to hundreds of meters. Radar data will be obtained from different satellites over different periods: ERS-1/2 data for 1991-2000; Envisat data for 2002-2010; ALOS data for 2006-2011, and the Sentinel-1 data for 2013-2014. The Sentinel-1 mission is scheduled to launch in 2013. Thus, we will be able to provide ReSALT data over two decades across the study area. The ReSALT products obtained from this project will, in effect, expand the CALM network from individual sites to the regional scale.

The high resolution ReSALT product can serve as validation data set for models attempting to simulate active layer and permafrost dynamics and their impacts on terrestrial ecosystems within the ABoVE domain. A ReSALT data set would serve as an invaluable planning tool by identifying the areas with the large changes in ALT and significant losses or gains of ground ice. This would help identify the best sites to study thermokarst development, surface hydrological processes, and terrestrial ecosystem dynamics within the proposed ABoVE domain. These sites could be the focus of the proposed in situ observations, aircraft measurements, and satellite remote sensing studies.

The ReSALT products meet the requirements of the NASA Terrestrial Ecology program: (a) Data set development in support of ABoVE research to be conducted in a future Terrestrial Ecology Program-sponsored field campaign, (b) Data set development to meet priority needs for the NASA terrestrial ecological community.

All data products generated from this study will be archived at the NASA National Snow and Ice Data Center DAAC and available to the Arctic research community.

Related Resources

NASA Arctic-Boreal Vulnerability Experiment (ABoVE)

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