Mass gains of the Antarctic ice sheet exceed losses

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 0.23 mm a(-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.