In situ measurements of freeze/thaw ground displacement in the Lena River Delta, 2013-2017, using steel pipes

In permafrost areas, seasonal freeze-thaw cycles of active layer result in upward and downward movements of the ground. Additionally, relatively uniform thawing of the ice-rich layer at the permafrost table can contribute to net long-term surface lowering. We use a simple method to quantify surface lowering (subsidence) and uplift in a yedoma area of the Lena River Delta, Siberian Arctic (Kurungnakh Island), using reference rods (metal pipes and fiberglass rods) installed deeply in permafrost. The metal pipes were 2 m long and 3 cm in diameter and were anchored at least 1 m below the typical active layer. The fiberglass rods were 2 m long and 1 cm in diameter and were anchored at least 70 m below the typical active layer. We assume, therefore, that the rods were motionless relative to the permafrost. The plexiglass plate with a size of 10 by 10 cm was fixed in its horizontal position by the rod but could move freely with the surface vertically along the rod. We repeatedly measured distance between the top of a rod and a plexiglass plate resting on the ground surface. Several distance measurements around each rod were taken at each visit and averaged. Altogether 12 metal pipes were installed at the study site in April 2013 and 19 fiberglass rods were installed in April 2014. Measurements were conducted during field campaigns from spring 2013 to summer 2017 with some gaps. We provide here the measured distances between the top of a rod and a plexiglass plate. To obtain the ground displacement, the user have to define the period of interest and calculate the displacement.

在多年冻土（permafrost）区域，活动层（active layer）的季节性冻融循环会引发地面的升降运动。此外，多年冻土上限（permafrost table）处富冰层的相对均匀融化，会导致地表产生长期净沉降。我们采用一种简便方法，对西伯利亚北极地区勒拿河三角洲库伦纳克岛（Kurungnakh Island）的雅科德马（yedoma）区域的地表沉降与抬升进行量化：通过深埋于多年冻土中的参考杆（reference rods，包含金属管与玻璃纤维杆）开展观测。所用金属管长2米、直径3厘米，锚定深度至少位于典型活动层下方1米处；玻璃纤维杆长2米、直径1厘米，锚定深度至少位于典型活动层下方70米处。据此我们假设，参考杆相对于多年冻土保持静止。尺寸为10×10厘米的有机玻璃板（plexiglass plate）由参考杆固定为水平状态，可随地表沿参考杆垂直自由移动。我们反复测量参考杆顶端与置于地表的有机玻璃板之间的距离。每次野外考察时，我们会在每根参考杆周边多次采集距离数据并取平均值。本研究于2013年4月在研究区域布设了12根金属管，2014年4月布设了19根玻璃纤维杆。观测工作于2013年春季至2017年夏季期间的多场次野外考察中开展，期间存在部分观测间隙。本数据集提供了参考杆顶端与有机玻璃板之间的实测距离数据。使用者可根据目标研究时段，通过计算得到地表位移量。