Cooper Matthew G, Smith Laurence C, Rennermalm Åsa K, Ryan Jonathan C, Pitcher Lincoln H, Liston Glen E, Miège Clément, Cooley Sarah W, van As Dirk
Department of Geography, University of California, Los Angeles, CA, USA.
Sierra Crest Analytics, Portland, OR, USA.
Nat Commun. 2025 Sep 12;16(1):8273. doi: 10.1038/s41467-025-62281-0.
The contribution of Greenland Ice Sheet meltwater runoff to global sea-level rise is accelerating due to increased melting of its bare-ice ablation zone. There is growing evidence, however, that climate models overestimate runoff from this critical area of the ice sheet. Climate models traditionally assume that all bare-ice runoff enters the ocean, unlike porous firn, in which some meltwater is retained and/or refrozen. We used field measurements and numerical modeling to reveal that extensive retention and refreezing also occurs in bare glacier ice. We found that, from 2009 to 2018, meltwater refreezing in bare, porous glacier ice reduced runoff by an estimated 11-17 Gt a in southwest Greenland alone, equivalent to 9-15% of this sector's annual meltwater runoff simulated by climate models. This mass retention explains evidence from prior studies of runoff overestimation on bare ice by current generation climate models and may represent an overlooked buffer on projected runoff increases. Inclusion of bare-ice retention and refreezing processes in climate models therefore has immediate potential to improve forecasts of ice sheet runoff and its contribution to sea-level rise.
由于格陵兰冰盖裸冰消融区融化加剧，其融水径流对全球海平面上升的贡献正在加速。然而，越来越多的证据表明，气候模型高估了冰盖这一关键区域的径流。传统气候模型假设，与多孔积雪不同，所有裸冰径流都会流入海洋，而在多孔积雪中，一些融水会被保留和/或重新冻结。我们通过实地测量和数值模拟发现，裸冰川冰中也存在广泛的水分保留和重新冻结现象。我们发现，在2009年至2018年期间，仅在格陵兰岛西南部，裸的多孔冰川冰中的融水重新冻结就使径流减少了约11-17亿吨/年，相当于该区域气候模型模拟的年融水径流量的9-15%。这种质量保留解释了先前研究中关于当代气候模型高估裸冰径流的证据，并且可能代表了预计径流增加中一个被忽视的缓冲因素。因此，在气候模型中纳入裸冰保留和重新冻结过程，有可能立即改善对冰盖径流及其对海平面上升贡献的预测。
