A Test of Recent Inferences of Net Polar Ice Mass Balance based on Long-Wavelength Gravity

E. Morrow, J. X. Mitrovica, M. G. Sterenborg, C. Harig
2013 Journal of Climate  
A comprehensive analysis of satellite datasets has estimated that the ice sheets of Greenland, West Antarctica, the Antarctic Peninsula, and East Antarctica experienced a net mass loss of 2100 6 92 Gt yr 21 over the period 1992-2000 and 2298 6 58 Gt yr 21 over the period 2000-11, representing an increase of 2198 6 109 Gt yr 21 between the two epochs. The authors demonstrate that the time rate of change of the degreefour zonal harmonic of Earth's gravitational potential _ J 4 provides an
more » ... provides an independent check on these mass balances that is less sensitive to uncertainties that have contaminated previous analyses of the degree-2 zonal harmonic [e.g., due to ongoing glacial isostatic adjustment (GIA), solid Earth body tides, and core-mantle coupling]. For the period 2000-11, the _ J 4 signal implied by the ice sheet mass flux cited above is (3.8 6 0.6) 3 10 211 yr 21 , whereas the change in the _ J 4 harmonic across the two epochs is (2.3 6 1.1) 3 10 211 yr 21 . In comparison, using satellite laser ranging (SLR) data, the authors estimate a GIA-corrected _ J 4 value of (3.8 6 0.6) 3 10 211 yr 21 for the epoch 2000-11 and a change across the two epochs of (5.3 6 1.6) 3 10 211 yr 21 . The authors conclude that the former supports recent estimates of melting over the last decade, whereas the latter suggests either that estimated melt rates for the earlier epoch were too high or that the uncertainty associated with the SLR-based inference of _ J 4 during the earlier epoch is underestimated.
doi:10.1175/jcli-d-13-00078.1 fatcat:jpbxx3hsmfek3posg2gjgtzi6q