Jakobshavn Glacier Bed Elevation

Jakobshavn Isbræ, West Greenland, which holds a 0.6-m sea level volume
equivalent, has been speeding up and retreating since the late 1990s.
Interpretation of its retreat has been hindered by difficulties in
measuring its ice thickness with airborne radar depth sounders. Here, we
employ high-resolution, helicopter-borne gravity data from 2012 to
reconstruct its bed elevation within 50 km of the ocean margin using a
three-dimensional inversion constrained by fjord bathymetry data offshore
and a mass conservation algorithm inland. We find the glacier trough to be
asymmetric and several 100 m deeper than estimated previously in the lower
part. From 1996-2016, the grounding line migrated at 0.6 km/yr from 700 m
to 1,100 m depth. Upstream, the bed drops to 1,600 m over 10 km then
slowly climbs to 1,200 m depth in 40 km. Jakobshavn Isbræ will continue to
retreat along a retrograde slope for decades to come. An L., E.
Rignot, S.H.P. Elieff, M. Morlighem, R.
Millan, J. Mouginot, D.M. Holland, D. Holland,
and J. Paden (2017), Bed elevation of
Jakobshavn Isbræ, West Greenland, from high-resolution airborne gravity
and other data, Geophys. Res.
Lett., 44, doi:10.1002/2017GL073245.