One key barometer within the climate change debate is the melting of ice in glacier-dominated regions, such as Greenland and Antarctica. The United States National Aeronautics and Space Administration (NASA) applies the scientific method to this controversy, using two technology approaches to measure glacial changes occurring in these areas. The first involves two satellites, which help pinpoint glaciers’ role in sea-level rise. The second is a robot that will roam over Greenland’s landscape to detect changes in the ice sheet.
Using satellites, a new study of glaciers worldwide compares traditional ground measurements to satellite data from NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat) and Gravity Recovery and Climate Experiment (GRACE) missions. The study, which estimates ice loss for glaciers in all regions of the planet, spans from 2003 to 2009 (when the two missions overlapped).
ICESat stopped operating in 2009. It measured glacier change through laser altimetry, which bounces laser pulses off the ice surface to inform the satellite of changes in the height of the ice cover. A successor, ICESat-2, is scheduled to launch in 2016. GRACE is still operational; it detects variations in the Earth’s gravity field resulting from changes in the planet’s mass distribution, including ice displacements.
Overall results of the study show that glaciers outside of the Greenland and Antarctic ice sheets, which constitute 1% of all land ice, lost an average of 571 trillion pounds of mass every year during the six-year study period. Thus, the oceans rose 0.03 in. per year, equating to about 30% of the total observed global sea-level rise during this period. Antarctica’s peripheral glaciers (small ice bodies not connected to the main ice sheet) contributed little to sea-level rise during that timeframe.
The analysis builds on a 2012 study using only GRACE data, which also found glacier ice loss was less than estimates derived from ground-based measurements. According to the study, though GRACE has inadequate resolution and ICESat lacks sufficient sampling density to study small glaciers, the two satellites’ estimates of mass change for large glaciered regions agree well.
