Landscape and Permafrost Changes in the Prudhoe Bay Oilfield, Alaska (1949-2011)

Many areas of the Arctic are simultaneously affected by rapid climate change and rapid industrial development.These areas are likely to increase in number and size as sea ice melts and abundant Arctic natural resources become more accessible. Documenting the changes that have already occurred is essential to inform management approaches to minimize the impacts of future activities. Here, we determine the cumulative geoecological effects of 62 years (1949-2011) of infrastructure- and climate-related changes in the Prudhoe Bay Oilfield, the oldest and most extensive industrial complex in the Arctic, and an area with extensive ice-rich permafrost that is extraordinarily sensitive to climate change. We demonstrate that thermokarst has recently affected broad areas of the entire region, and that a sudden increase in the area affected began shortly after 1990 corresponding to a rapid rise in regional summer air temperatures and related permafrost temperatures. We also present a conceptual model that describes how infrastructure-related factors, including road dust and roadside flooding are contributing to more extensive thermokarst in areas adjacent to roads and gravel pads. We mapped the historical infrastructure changes for the Alaska North Slope oilfields for 10 dates from the initial oil discovery in 1968-2011. By 2010, over 34% of the intensively mapped area was affected by oil development. In addition, between 1990 and 2001, coincident with strong atmospheric warming during the 1990s, 19% of the remaining natural landscapes (excluding areas covered by infrastructure, lakes and river floodplains) exhibited expansion of thermokarst features resulting in more abundant small ponds, greater microrelief, more active lakeshore erosion and increased landscape and habitat heterogeneity. This transition to a new geoecological regime will have impacts to wildlife habitat, local residents and industry.

北极诸多区域正同时遭受快速气候变化与快速工业发展的双重影响。随着海冰消融、北极丰富的自然资源更易于开发利用，这类区域的数量与规模或将进一步扩张。记录已发生的环境变化，可为制定管理方案以最大程度降低未来人类活动的负面影响提供依据。本研究针对北极地区历史最久、规模最大的工业综合体——普拉德霍湾油田（Prudhoe Bay Oilfield）展开分析，该区域分布有大面积对气候变化极为敏感的富冰多年冻土（ice-rich permafrost），明确了1949年至2011年共62年间，该区域内与基础设施建设及气候变化相关的各类变化所带来的累积地质生态效应。研究表明，近期热融喀斯特（thermokarst）已波及整个区域的大范围地块；1990年后不久，受影响区域面积突然激增，这与区域夏季气温快速上升及相应的多年冻土温度升高高度吻合。本研究还提出了一套概念模型，用以阐释道路扬尘、路边积水等与基础设施相关的因素，如何加剧道路周边与砾石平台（gravel pads）区域的热融喀斯特发育规模。我们针对1968年首次发现石油至2011年的10个时间节点，绘制了阿拉斯加北坡油田的历史基础设施变化图谱。至2010年，经精细测绘的区域内已有超过34%的面积受到石油开发活动的影响。此外，在1990年至2001年——这一时期与20世纪90年代的强烈大气变暖时段重合——剩余自然景观（不含基础设施覆盖区域、湖泊与河流漫滩）中已有19%出现热融喀斯特特征扩张，表现为小型水塘数量增多、微地貌更复杂、湖岸侵蚀更为活跃，以及景观与生境异质性提升。这种向新型地质生态系统状态的转变，将对野生生物栖息地、当地居民及工业发展产生诸多负面影响。