Tedstone Andrew, Machguth Horst, Clerx Nicole, Jullien Nicolas, Picton Hannah, Ducrey Julien, van As Dirk, Colosio Paolo, Tedesco Marco, Lhermitte Stef
Department of Geosciences, University of Fribourg, Fribourg, Switzerland.
Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland.
Nat Commun. 2025 May 14;16(1):4494. doi: 10.1038/s41467-025-59237-9.
Rivers and slush fields on the Greenland Ice Sheet increasingly develop in locations where the accumulation zone hosts near-impermeable ice slabs. However, the division between runoff versus retention in these areas remains unmeasured. We present field measurements of superimposed ice formation onto slabs around the visible runoff limit. The quantity of superimposed ice varies by proximity to visible surface water and the surface slope, highlighting that meltwater can flow laterally before refreezing. We use heat conduction modelling and radar observations of autumn wetness to show that in our field area in 2022, 65% of superimposed ice formed during summer and the rest during autumn in the relict supraglacial hydrological network. Overall, 84% of melt around the visible runoff limit refroze. Ice-sheet-wide we estimate that slabs refroze 56 gigatonnes of melt (26-69 gigatonnes according to slab extent) between 2017 and 2022. Slabs are thus both hotspots of refreezing and emerging zones of runoff.
格陵兰冰原上的河流和融雪区越来越多地出现在积累区存在近乎不透水冰板的地方。然而，这些地区径流与滞留之间的划分仍未得到测量。我们展示了在可见径流界限周围的冰板上叠加冰形成的实地测量结果。叠加冰的数量因与可见地表水的距离和地表坡度而异，这突出表明融水在重新冻结之前可以横向流动。我们利用热传导模型和秋季湿度的雷达观测结果表明，在2022年我们的实地研究区域，65%的叠加冰在夏季形成，其余的在秋季形成于残留的冰上水文网络中。总体而言，可见径流界限周围84%的融水重新冻结。据我们估计，在2017年至2022年期间，整个冰原上的冰板重新冻结了560亿吨融水（根据冰板范围为260亿至690亿吨）。因此，冰板既是重新冻结的热点区域，也是径流出现的区域。
