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Mass changes of the Antarctic ice sheet impact sea-level rise as climate changes, but recent rates have been uncertain. Ice, Cloud and land Elevation Satellite (ICESat) data (2003-08) show mass gains from snow accumulation exceeded discharge losses by 82±25 Gt a-1, reducing global sea-level rise by 0.23mma-1. European Remote-sensing Satellite (ERS) data (1992-2001) give a similar gain of 112±61 Gt a-1. Gains of 136 Gt a-1 in East Antarctica (EA) and 72 Gt a-1 in four drainage systems (WA2) in West Antarctic (WA) exceed losses of 97 Gt a-1 from three coastal drainage systems (WA1) and 29 Gt a-1 from the Antarctic Peninsula (AP). EA dynamic thickening of 147 Gt a-1 is a continuing response to increased accumulation (>50%) since the early Holocene. Recent accumulation loss of 11 Gt a-1 in EA indicates thickening is not from contemporaneous snowfall increases. Similarly, the WA2 gain is mainly (60 Gt a-1) dynamic thickening. In WA1 and the AP, increased losses of 66±16 Gt a-1 from increased dynamic thinning from accelerating glaciers are 50% offset by greater WA snowfall. The decadal increase in dynamic thinning in WA1 and the AP is approximately one-third of the long-term dynamic thickening in EA and WA2, which should buffer additional dynamic thinning for decades. [ABSTRACT FROM AUTHOR]

A response from the authors of the article "Mass Gains of the Antarctic Ice Sheet exceed Losses," in the 2015 issue is presented.

A response from the authors of the article " Mass gains of the Antarctic ice sheet exceed losses" in the 2015 issue is presented.

Vertical displacements of emerged land caused by oceanic tidal loading are of the order of several tens of millimetres in polar regions. They constitute a long wavelength signal, the amplitude of which is comparable to elevation changes that might be associated with climate-driven changes in ice-sheet volume. Using bilinear interpolation on a 1° by 1° global grid, we examine the amplitudes and phases of vertical displacements caused at any given epoch by the eight most important ocean tide constituents of recent ocean tide models, extrapolated to high latitudes. This permits estimation of the oceanic tidal loading corrections to measurements made by a satellite altimeter along the satellite ground track. We have done so systematically over Antarctica, for a scenario flight of ICESAT, which carries the Geoscience Laser Altimeter System (GLAS), whose primary science goal is to monitor ice-sheet mass balance. Ocean loading tide corrections near the coast of Antarctica can reach several centimetres; overall they average about 10 min. [ABSTRACT FROM PUBLISHER]