Abstract
[1] The delineation of an ice sheet grounding line, i.e., the transition boundary where ice detaches from the bed and becomes afloat in the ocean, is critical to ice sheet mass budget calculations, numerical modeling of ice sheet dynamics, ice-ocean interactions, oceanic tides, and subglacial environments. Here, we present 15 years of comprehensive, high-resolution mapping of grounding lines in Antarctica using differential satellite synthetic-aperture radar interferometry (DInSAR) data from the Earth Remote Sensing Satellites 1–2 (ERS-1/2), RADARSAT-1 and 2, and the Advanced Land Observing System (ALOS) PALSAR for years 1994 to 2009. DInSAR directly measures the vertical motion of floating ice shelves in response to tidal oceanic forcing with millimeter precision, at a sample spacing better than 50 m, simultaneously over areas several 100 km wide; in contrast with earlier methods that detect abrupt changes in surface slope in satellite visible imagery or altimetry data. On stagnant and slow-moving areas, we find that breaks in surface slope are reliable indicators of grounding lines; but on most fast-moving glaciers and ice streams, our DInSAR results reveal that prior mappings have positioning errors ranging from a few km to over 100 km. A better agreement is found with ICESat's data, also based on measurements of vertical motion, but with a detection noise one order of magnitude larger than with DInSAR. Overall, the DInSAR mapping of Antarctic grounding lines completely redefines the coastline of Antarctica.
Highlights
[2] The grounding line, G, is the transition boundary between ice in contact with the bed and ice afloat in the ocean waters
With glacier slopes typically lower than 1% in the transition region, meter‐scale changes in ice thickness translate into grounding line migrations of 100m’s, i.e., two orders of magnitude larger, which is detectable with differential satellite radar interferometry (DInSAR) [Rignot, 1998a]
[5] Here, we summarize 15 years of DInSAR mapping in Antarctica using a suite of satellites that provide the first complete, high‐precision, uniform sampling mapping of all Antarctic grounding lines, including areas south of 81°S covered for the first time in 2009
Summary
[2] The grounding line, G, is the transition boundary between ice in contact with the bed and ice afloat in the ocean waters. [3] Knowing the position of the grounding line is critical for mass budget calculations because it determines the precise location of where ice detaches from the bed and becomes afloat in the ocean, typically far upstream (10 to 1,000 km) from where ice calves into icebergs. [4] The grounding line is a fundamental transition for ice dynamics It is the locus of a major shift in ice flow from shear‐dominated, basal‐drag‐controlled ice stream flow to drag‐free, side‐shear‐controlled, gravity spreading of floating ice shelves onto the ocean. With glacier slopes typically lower than 1% in the transition region, meter‐scale changes in ice thickness translate into grounding line migrations of 100m’s, i.e., two orders of magnitude larger, which is detectable with DInSAR [Rignot, 1998a]. We compare our results with prior mappings and discuss the impact of our findings on our general knowledge of the Antarctic coastline
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
