Principal Investigator (PI): Ian Joughin, University of Washington, Seattle
The technology for measuring velocity in Greenland is mature, as demonstrated through our ongoing and past Greenland Ice Mapping Projects 1 and 2 (GIMP-1 and 2). These projects repeatedly measured ice velocity in Greenland, establishing a record from 2000 to present. With GIMP-3, we will continue this effort to extend the record of ice flow velocity through 2022, a period when Greenland is expected to continue to evolve rapidly with the current warming.
Numerous studies have revealed rapid changes in ice discharge from Greenland, with many of the ice sheet’s outlet glaciers accelerating dramatically over the last two decades. These observations are significant in that they show Greenland’s mass balance can fluctuate rapidly and unpredictably.
Despite the magnitude of these changes, we do not yet understand the underlying processes controlling fast flow well enough to determine their long-term impact on sea level. Observations made over the last several years, including those from our prior projects, indicate less potential for run-away ice loss than was initially feared when the first observations of rapid change were made. Nonetheless, outlet glacier dynamics remain a “wild card” in the sea-level projections, as noted in the last two Intergovernmental Panel on Climate Change (IPCC) assessments.
Improving such predictions and gaining a firm understanding of the dynamics that drive mass balance requires annual to sub-annual observations of outlet glacier variability (velocity, elevation, and ice front position) to avoid aliasing of the rapidly varying signals. Furthermore, although glaciers can change far more rapidly (sub-annual scales) than expected, decadal-scale observations are still required to provide the knowledge needed for century-scale projection.
The GIMP-3 products will be entirely compatible with prior products, but we will take advantage of new sensors that have been launched in the last 5 years (Landsat 8, Sentinel-1A/B and Sentinel-2A/B) to greatly improve temporal and spatial sampling.
We will also take advantage of the improved availability of Landsat Thematic Mapper (TM) data to extend the record back in time to 1984. In conjunction with the results from our earlier projects, GIMP-3 will provide an important nearly four-decade-long precursor data set for the NASA-Indian Space Research Organisation L-band Synthetic Aperture Radar (NISAR) mission scheduled to launch near the end of the decade as a joint effort between NASA and ISRO. In addition, GIMP-3 velocity measurements will provide a strong complement to the thinning measurements made by NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) and IceBridge missions.