Albedo-a primary control on surface melt-varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo along a 25 km transect dissecting the western, ablating sector of the ice sheet. Our results demonstrate that distributed surface impurities-an admixture of dust, black carbon and pigmented algae-explain 73% of the observed spatial variability in albedo and are responsible for the dark zone itself. Crevassing and supraglacial water also drive albedo reduction but due to their limited extent, explain just 12 and 15% of the observed variability respectively. Cryoconite, concentrated in large holes or fluvial deposits, is the darkest surface type but accounts for <1% of the area and has minimal impact. We propose that the ongoing emergence and dispersal of distributed impurities, amplified by enhanced ablation and biological activity, will drive future expansion of Greenland's dark zone.

中文翻译：

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格陵兰冰盖的暗区由分布的生物活性杂质控制。


反照率（表面融化的主要控制因素）在整个格陵兰冰盖上变化很大，但构成其暗区的特定表面类型仍然无法量化。在这里，我们使用无人机图像将七种不同的表面类型归因于沿 25 公里长的横断面观察到的反照率，该横断面剖析了冰盖西部消融部分。我们的结果表明，分布的表面杂质（灰尘、黑碳和色素藻类的混合物）解释了观察到的反照率空间变化的 73%，并且是暗区本身的原因。裂缝和冰上水也导致反照率降低，但由于其范围有限，分别只能解释观测到的变异性的 12% 和 15%。冰灰石集中在大孔或河流沉积物中，是最暗的表面类型，但占面积的<1%，影响最小。我们认为，分布式杂质的持续出现和扩散，通过增强的消融和生物活动而放大，将推动格陵兰暗区的未来扩张。