Interannual variations in meltwater input to the Southern Ocean from Antarctic ice shelves.

Ocean-driven basal melting of Antarctica’s floating ice shelves accounts for about half of their mass loss in steady-state, where gains in ice shelf mass are balanced by losses. Ice shelf thickness changes driven by varying basal melt rates modulate mass loss from the grounded ice sheet and its contribution to sea level, and the changing meltwater fluxes influence climate processes in the Southern Ocean. Existing continent-wide melt rate datasets have no temporal variability, introducing uncertainties in sea level and climate projections. Here, we combine surface height data from satellite radar altimeters with satellite-derived ice velocities and a new model of firn-layer evolution to generate a high-resolution map of time-averaged (2010–2018) basal melt rates, and time series (1994–2018) of meltwater fluxes for most ice shelves. Total basal meltwater flux in 1994 (1090±150 Gt/yr) was not significantly different from the steady-state value (1100±60 Gt/yr), but increased to 1570±140 Gt/yr in 2009, followed by a decline to 1160±150 Gt/yr in 2018. For the four largest “cold-water” ice shelves we partition meltwater fluxes into deep and shallow sources to reveal distinct signatures of temporal variability, providing insights into climate forcing of basal melting and the impact of this melting on the Southern Ocean.

在稳定状态下，南极漂浮冰架由海洋驱动的底部融化约占其质量损失的一半，此时冰架质量的增加与损失相平衡。由底部融化速率变化驱动的冰架厚度变化调节着接地冰盖的质量损失及其对海平面的影响，而不断变化的融水通量影响着南大洋的气候过程。现有的全大陆融化速率数据集没有时间变异性，这给海平面和气候预测带来了不确定性。在此，我们将卫星雷达高度计的表面高度数据与卫星得出的冰流速以及一个新的积雪层演变模型相结合，生成了一个大多数冰架的时间平均（2010 - 2018年）底部融化速率的高分辨率地图，以及融水通量的时间序列（1994 - 2018年）。1994年的总底部融水通量（1090±1500亿吨/年）与稳定状态值（1100±600亿吨/年）没有显著差异，但在2009年增加到1570±1400亿吨/年，随后在2018年下降到1160±1500亿吨/年。对于四个最大的“冷水”冰架，我们将融水通量划分为深层和浅层来源，以揭示时间变异性的不同特征，从而深入了解底部融化的气候驱动因素以及这种融化对南大洋的影响。