Greenland is capped with a vast ice sheet that spans 1.7 million square kilometers (656,000 square miles) and measures more than 3 kilometers (1.9 miles) at its thickest point. Below all this ice lies a landscape human eyes have never seen directly. But a newly developed method for mapping this hidden bedrock has produced the most detailed and accurate view of it yet.
格陵兰岛覆盖着巨大的冰盖，面积达 170 万平方公里（656,000 平方英里），最厚处超过 3 公里（1.9 英里）。在所有这些冰层下面，隐藏着人类肉眼从未直接见过的景观。但是，一种新开发的绘制这个隐藏基岩地图的方法已经产生了迄今为止最详细和准确的视图。
The new map reveals an expansive network of valleys carved into the surface beneath the Greenland Ice Sheet. Many of the features formed well before most of the ice above them existed, offering new context for the island’s geologic history—and potentially helping scientists refine projections of the ice sheet’s future. Scientists described the newly mapped valleys in a NASA-led paper published in Geophysical Research Letters .
新地图揭示了格陵兰冰盖下方的广阔山谷网络。许多特征早在其上方的大部分冰存在之前就已形成，为该岛的地质历史提供了新的背景，并可能帮助科学家完善对冰盖未来的预测。科学家们在美国宇航局主导的《地球物理研究快报》上发表的一篇论文中描述了新绘制的山谷。
The map, shown above, was derived from a method called Ice Flow Perturbation Analysis. As ice flows over a valley or ridge, the topography leaves a faint signature on the ice surface. Satellites map the ice surface in fine detail, and scientists can use these subtle bumps and dips to infer the shape of the landscape buried below. The work aims to improve future versions of BedMachine Greenland , a high-resolution dataset of the terrain beneath the ice sheet.
上图所示的地图源自一种名为“冰流扰动分析”的方法。当冰流过山谷或山脊时，地形会在冰表面留下微弱的痕迹。卫星详细地绘制了冰面的地图，科学家可以利用这些微妙的凹凸和凹陷来推断埋藏在下面的地貌的形状。这项工作旨在改进 BedMachine Greenland 的未来版本，这是冰盖下地形的高分辨率数据集。
Using the technique, researchers manually mapped 1,943 subglacial valleys beneath the Greenland Ice Sheet, about a third of which are newly identified. About half of the valleys included in BedMachine Greenland, primarily near the ice sheet’s edge, are now known to extend farther inland than that map indicates, in some cases by hundreds of kilometers.
利用该技术，研究人员手动绘制了格陵兰冰盖下 1,943 个冰下山谷的地图，其中约三分之一是新发现的。 BedMachine 格陵兰岛大约一半的山谷（主要靠近冰盖边缘）现在已知向内陆延伸的距离比地图所示的更远，在某些情况下延伸了数百公里。
Some aspects of the new map align with the current understanding of how Greenland’s landscapes formed. For instance, many of the valleys appear to begin in the southern and eastern highlands, where the ice sheet is thought to have first formed. Near the eastern highlands, the map reveals a mountain range beneath the ice, with interconnected valleys and relief that increases toward the coast. These alpine-style landforms may have survived under the ice since at least the Pliocene.
新地图的某些方面与目前对格陵兰岛地貌形成方式的理解相符。例如，许多山谷似乎始于南部和东部高地，人们认为冰盖首先在那里形成。在东部高地附近，地图显示了冰层下的山脉，山谷相互连接，地势向海岸逐渐增加。这些高山风格的地貌可能至少从上新世就在冰层下幸存下来。
Other aspects of the topography are more puzzling. The analysis indicates numerous valleys, especially in the west-central region, that are long, straight, and consistently aligned in a southwest-northeast direction. This orientation suggests a tectonic influence, generating preferential pathways along which water could flow and valleys could form. “That’s a riddle to us,” said Joe MacGregor, a NASA cryospheric scientist and co-author of the study. “Greenland is justifiably usually treated as a rigid block of old rock that is simply translated as needed to accommodate the motion and interactions of other tectonic plates.”
地形的其他方面更令人费解。分析表明，有许多山谷，特别是在中西部地区，这些山谷又长又直，并且始终沿西南-东北方向排列。这种方向表明了构造的影响，产生了水可以流动和山谷形成的优先路径。 “这对我们来说是一个谜，”美国宇航局冰冻圈科学家、该研究的合著者乔·麦格雷戈说。 “格陵兰岛通常被合理地视为一块坚硬的古老岩石，可以根据需要简单地平移以适应其他构造板块的运动和相互作用。”
Separately, the angles at which the valleys branch offer another insight into their origin. Their relatively wide branching angles suggest that surface water didn’t act alone; instead, a widespread groundwater network—seeping upward and eroding the surrounding rock—likely helped carve the valleys before the ice sheet formed.
另外，山谷分支的角度提供了对其起源的另一种见解。它们相对较宽的分支角度表明地表水并不是单独作用的；相反，广泛的地下水网络向上渗透并侵蚀周围的岩石，可能在冰盖形成之前帮助雕刻了山谷。
Mapping these valleys matters for understanding the ice sheet, which has continued to dramatically reshape the landscape. Ice flow concentrates in valleys, where it forms glaciers that eventually calve into fjords at the periphery of the ice sheet. This creates a reinforcing cycle: ice funneling through a valley gets thicker, thicker ice flows faster, and faster flow carves the valley even deeper.
绘制这些山谷的地图对于了解冰盖很重要，冰盖继续极大地重塑着地貌。冰流集中在山谷中，在那里形成冰川，最终在冰盖边缘崩解成峡湾。这就形成了一个强化循环：穿过山谷的冰变得更厚，更厚的冰流动得更快，更快的流动将山谷雕刻得更深。
This carving power is especially evident along western Greenland. MacGregor likened it to the glacially incised landscape at Yosemite, with Greenland’s western coast resembling, as he put it, “El Capitan after El Capitan.”
这种雕刻能力在格陵兰岛西部地区尤其明显。麦格雷戈将其比作优胜美地冰川切割的景观，用他的话说，格陵兰岛的西海岸就像“一个又一个的酋长岩”。
Studying the valleys also matters for the ice sheet’s future. Because the relationship between ice flow and valleys is well understood, scientists expect that as the ice sheet retreats, flow will continue to concentrate wherever the valleys already are. “The better we understand the topography now,” MacGregor said, “the better sense we’ll have of what it will look like in the longer term—beyond the next decade or two—as faster ice flow propagates into Greenland’s interior.”
研究山谷对于冰盖的未来也很重要。由于冰流与山谷之间的关系已广为人知，科学家预计，随着冰盖后退，冰流将继续集中在山谷所在的地方。 “我们现在对地形了解得越多，”麦格雷戈说，“随着冰流更快地传播到格陵兰岛内陆，我们就能更好地了解未来一两年之后的长期情况。”
NASA Earth Observatory map by Lauren Dauphin using data from Chartrand et al . Story by Kathryn Hansen.
NASA 地球观测站地图由 Lauren Dauphin 使用 Chartrand 等人的数据绘制。凯瑟琳·汉森的故事。