深入理解泛北极地区多年冻土活动层厚度的演变, 对于全球碳通量模拟、气候变化预测及泛北极地区冻融风险评估具有重要意义。目前开展的泛北极地区多年冻土活动层厚度模拟与分析, 大多无法全覆盖或空间分辨率过低(25 km或是更大), 在景观尺度(公里级)上的多年冻土活动层厚度变化特征仍有待解析, 尤其是关键基础设施区的活动层厚度变化仍不清楚。本研究基于站点监测数据、MOD11B3地表温度数据、MCD12C1土地覆盖数据, 采用Stefan模型, 在公里级空间分辨率上模拟泛北极地区2001年—2017年多年冻土活动层厚度, 并解析泛北极地区及主要油气区多年冻土活动层厚度时空变化格局及主要原因。研究发现: 2001年—2017年泛北极地区约有78.4%的冻土区域多年冻土活动层厚度呈现增长趋势, 尽管全区多年平均的增长速率为0.22 cm/a (p<0.05), 但具有较强的时空差异性。显著增长区主要集中在加拿大西北部的落基山脉及劳伦琴高原一带以及俄罗斯中西伯利亚高原中部地区, 增加速率主要在0.5—1 cm/a；而减少区主要分布在加拿大的哈得孙湾沿岸平原、拉布拉多高原一带, 俄罗斯的东西伯利亚山地北部、中西伯利亚高原的北部、贝加尔湖以东区域和泰拉尔半岛一带。泛北极地区主要油气区多年冻土活动层厚度也以增加为主, 80%以上的油气区呈现增加趋势, 增长速率在0.1—0.7 cm/a。泛北极地区多年冻土活动层厚度变化与气温变化在空间上具有较好的一致性；积雪厚度与活动层厚度关系复杂；不同植被类型的多年冻土活动层厚度有所差异(林地>草地>稀树草原>灌丛), 且多年冻土活动层厚度变化与植被转化方向一致。该成果将有助于深入理解北半球高纬度多年冻土区冻融格局, 尤其可为冻土区的油气设施冻融风险识别与防控提供参考。

Understanding of the spatiotemporal changes in permafrost Active Layer Thickness (ALT) in the Pan-Arctic region is important for global carbon flux simulation, climate change prediction, and freeze–thaw risk assessment. Many studies have been conducted on this subject. However, most previous works have relied on limited sites or regional simulation with a spatial resolution of 25 km or coarser. The spatiotemporal characteristics of ALT change at a landscape level needs to be explored, especially in the crucial infrastructure concentrated region. This study simulated the permafrost ALT in the Pan-Arctic region from 2001 to 2017 at kilometer level using Stefan method and permafrost site records, MOD11B3, and MCD12C1 data. Results showed that approximately 78.4% of the study area had an increase trend in ALT with a rate of 0.22 cm/a (p<0.05). Furthermore, the change in ALT spatially varied. The significantly increased areas were mainly distributed in Rocky Mountains, Laurentian Plateau of Canada, Central Siberian Plateau, and Central Siberian Plateau of Russia, with an increase rate between 0.5 and 1 cm/a. Meanwhile, the decreased areas were mainly concentrated in Hudson Bay Coastal Plain, Labrador Plateau of Canada, north East Siberian Mountains, north Central Siberian Plateau, east of Lake Baikal, and Taylor Peninsula of Russia. During this period, the ALT in 80% of the oil and gas areas had increased, with an increase rate between 0.1 and 0.7 cm/a. The variation in ALT was consistent with the temperature change. The ALT also varied with vegetation types in the order of ALT in forests > ALT in grasslands > ALT in savannahs > ALT in shrublands. However, the relationship between ALT and the thickness of snow cover was highly complicated. The results will deepen our understanding of the permafrost freeze–thaw pattern in the northern high latitudes and provide insights into the identification and prevention of freeze–thaw risk in the Pan-Arctic permafrost region.