Comparison of elevation change detection methods from ICESat altimetry over the Greenland Ice Sheet


first_imgEstimation of the surface elevation change of the Greenland Ice Sheet (GrIS) is essential for understanding its response to recent and future climate change. Laser measurements from the NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) created altimetric surveys of GrIS surface elevations over the 2003-2009 operational period of the mission. This paper compares four change detection methods using Release 634 ICESat laser altimetry data: repeat tracks (RTs), crossovers (XOs), overlapping footprints (OFPs), and triangulated irregular networks (TINs). All four methods begin with a consistently edited data set and yield estimates of volumetric loss of ice from the GrIS ranging from -193 to -269 km³/yr. Using a uniform approach for quantifying uncertainties, we find that volume change rates at the drainage system scale from the four methods can be reconciled within 1-σ uncertainties in just 5 of 19 drainage systems. Ice-sheet-wide volume change estimates from the four methods cannot be reconciled within 1-σ uncertainties. Our volume change estimates lie within the range of previously published estimates, highlighting that the choice of method plays a dominant role in the scatter of volume change estimates. We find that for much of the GrIS, the OFP and TIN methods yield the lowest volume change uncertainties because of their superior spatial distribution of elevation change rate estimates. However, the RT and XO methods offer inherent advantages, and the future work to combine the elevation change detection methods to produce better estimates is warranted.last_img read more

Glenn Close Talks A Delicate Balance and Her Return to Broadway


first_img Related Shows A Delicate Balance View Comments Glenn Close Show Closed This production ended its run on Feb. 22, 2015 Star Files Glenn Close is returning to Broadway in Edward Albee’s A Delicate Balance this month, starring opposite fellow Tony winner John Lithgow, and she’s loving the challenge. On her Today Show visit on October 6, Close told Matt Lauer, “all of us have come to the moment where you sink to you knees and roll on the floor.” Sometimes, even Oscar nominees resort to the fetal position. On her long-awaited return to the Great White Way after 20 years, Close says, “It’s where I think my home is, and it’s where you really have to come up with the goods. At this point in my career, I was incredibly motivated to come back—to be in a challenging show with remarkable actors around me.” You can catch her come up with the goods beginning October 20 at the Golden Theatre!last_img read more