Each summer, surface melting of the margin of the Greenland Ice Sheet exposes a distinctive visible stratigraphy that is related to past variability in subaerial dust deposition across the accumulation zone and subsequent ice flow toward the margin. Here we map this surface stratigraphy along the northern margin of the ice sheet using mosaicked Sentinel-2 multispectral satellite imagery from the end of the 2019 melt season and finer-resolution WorldView-2/3 imagery for smaller regions of interest. We trace three distinct transitions in apparent dust concentration and the top of a darker basal layer. The three dust transitions have been identified previously as representing late-Pleistocene climatic transitions, allowing us to develop a coarse margin chronostratigraphy for northern Greenland. Substantial folding of late-Pleistocene stratigraphy is observed but uncommon. The oldest conformal surface-exposed ice in northern Greenland is likely located adjacent to Warming Land and may be up to ~55 thousand years old. Basal ice is commonly exposed hundreds of metres from the ice margin and may indicate a widespread frozen basal thermal state. We conclude that the ice margin across northern Greenland offers multiple opportunities to recover paleoclimatically distinct ice relative to previously studied regions in southwestern Greenland.

中文翻译：

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格陵兰冰盖北缘地表暴露冰的年龄

每年夏天，格陵兰冰盖边缘的表面融化会暴露出一种独特的可见地层，这与过去在积聚区的陆上尘埃沉积的变化以及随后向边缘流动的冰流有关。在这里，我们使用 2019 年融化季节结束时镶嵌的 Sentinel-2 多光谱卫星图像和较小感兴趣区域的更高分辨率 WorldView-2/3 图像绘制了沿冰盖北缘的表面地层图。我们追踪了表观尘埃浓度和较暗基底层顶部的三个不同转变。这三个尘埃转变先前已被确定为代表晚更新世气候转变，使我们能够开发格陵兰北部的粗边缘年代地层学。观察到晚更新世地层的大量褶皱，但不常见。格陵兰岛北部最古老的保形地表暴露冰可能位于变暖地附近，并且可能长达约 5.5 万年。基底冰通常暴露在距离冰缘数百米的地方，可能表明存在广泛的冰冻基底热状态。我们得出结论，与先前研究的格陵兰西南部地区相比，格陵兰北部的冰缘为恢复古气候不同的冰提供了多种机会。