Near-surface wedges of massive ice commonly outline polygons in tundra lowlands, but such polygons have been difficult to identify on hillslopes because soil movement flattens the ridges and infills the troughs that form beside and above the ice wedges. Over the past three decades, the active layer has thickened near the western Arctic coast of Canada and consequent thawing of ice wedges has been detected by remote sensing for flat terrain but not, generally, on hillslopes. Annual field surveys (1996–2018) at the Illisarvik field site of thaw depth and ground surface elevation show the mean subsidence rate above hillslope ice wedges has been up to 32 mm a⁻¹ since thaw depth reached the ice-wedge tops in 2007. Annual mean ground temperatures at the site are about −3.0°C beneath late-winter snow depths characteristic of the ice-wedge troughs but about −5.3°C under conditions of the intervening polygons. The rate of thaw subsidence is high for natural, subaerial disturbances because meltwater from the ice wedges runs off downslope. The rate is constant, because the thickness of seasonally thawed ground above the ice wedges and the ice content of the ground remain the same while the troughs develop. Observations of changes in surface elevation in northern Banks Island between the late 1970s and 2019 show troughs on hillslopes where none was previously visible. Development of these troughs creates regional thermokarst landscapes, distinct from the widely recognized results of thawing relict glacier ice, that are now widespread over Canada's western Arctic coastlands. Recognition of ice-wedge occurrence and accelerated thaw subsidence on hillslopes is important in the design of infrastructure proposed for construction in rolling permafrost terrain.

中文翻译：

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加拿大北极西部山坡冰楔上方气候引起的解冻沉降的长期实地测量

在苔原低地，近地表的大块冰楔通常勾勒出多边形的轮廓，但在山坡上很难识别这种多边形，因为土壤运动使山脊变平并填充了冰楔旁边和上方形成的槽。在过去的 30 年里，活动层在加拿大北极西部海岸附近增厚，因此通过遥感检测到冰楔的解冻，适用于平坦的地形，但通常不在山坡上。Illisarvik 现场解冻深度和地表高程的年度现场调查（1996-2018）显示，山坡冰楔上方的平均沉降率已高达 32 mm a ^-1自 2007 年解冻深度达到冰楔顶部以来。 该地点的年平均地面温度在冰楔槽特征的晚冬雪深以下约为 -3.0°C，但在插入多边形的条件下约为 -5.3°C 。由于来自冰楔的融水从下坡流下，自然地下扰动的解冻沉降率很高。该速率是恒定的，因为冰楔上方季节性融化的地面的厚度和地面的冰含量在槽形成时保持不变。对 1970 年代末至 2019 年间班克斯岛北部地表高程变化的观察显示，山坡上出现了以前不可见的低谷。这些海槽的发展创造了区域性热岩溶景观，与广泛认可的冰川残冰融化的结果不同，现在广泛分布在加拿大西部北极海岸。山坡上冰楔的出现和加速融化沉降的识别对于在滚动的永久冻土地形中建造的基础设施的设计很重要。