Patterns of Discontinuous Permafrost Thaw in Peatlands

Climate warming in discontinuous permafrost peatlands is causing permafrost loss and changes in ecosystem dynamics at an unprecedented rate. Though rates of permafrost loss and landscape change have been widely documented based on remote sensing and field measurements, the local mechanisms of permafrost degradation remain under-studied. Data collected over three decades of research in the Scotty Creek study basin in the southern Northwest Territories of Canada was analyzed to find vertical conduction accounts for most vertical permafrost degradation, while advective processes are needed to describe thaw in features which are subject to seasonal flows. It was found that heat advection was necessary to describe lateral thaw rates, which are up to an order of magnitude greater than vertical thaw. Thaw from below, driven either by the geothermal gradient or groundwater flow, may account for up to 10 cm of permafrost thaw annually. Once these thaw mechanisms were established, the hydrologic, thermodynamic and geophysical function of taliks in different parts of the landscape were considered in light of the data collected at the and surrounding area. This analysis is supported through the use of ERT data detailing the subsurface permafrost structure. Data collected at Scotty Creek points to a pattern of talik evolution and permafrost degradation. This understanding of local thaw mechanisms and trajectory is an important first step in being able to predict distributed permafrost thaw in peatlands. This research data is associated with Scotty Creek Research Station, 50km south of Fort Simpson, in the Northwest Territories, Canada. Learn more about SCRS and its research at http://scottycreek.com.

不连续多年冻土泥炭地的气候变暖正以史无前例的速率引发多年冻土退化与生态系统动态变化。尽管学界已基于遥感与野外实测数据，对多年冻土退化速率与景观变化过程开展了大量记录，但多年冻土退化的局地机制仍有待深入研究。本研究对加拿大西北地区南部斯科蒂溪研究流域内30余年科研工作所采集的数据展开分析，结果显示垂直传导主导了绝大多数垂直方向的多年冻土退化，而平流过程则可解释受季节性水流影响区域的冻土融化过程。研究发现，热平流过程是解释侧向融化速率的关键因素——侧向融化速率可比垂直融化速率高出一个数量级。由地温梯度或地下水流驱动的底部融化，每年可造成多达10厘米的多年冻土退化。明确上述融化机制后，研究结合研究点及周边区域的采集数据，对景观不同位置处融区（talik）的水文、热力学与地球物理功能展开了分析。本次分析依托可表征地下多年冻土结构的电阻率层析成像（ERT）数据得以支撑。斯科蒂溪流域采集的数据揭示了融区演化与多年冻土退化的典型模式。对局地融化机制与演化轨迹的这一认知，是实现泥炭地分布式多年冻土融化预测的重要基础性第一步。本研究数据集隶属于加拿大西北地区辛普森堡以南50公里的斯科蒂溪科研站（Scotty Creek Research Station, SCRS）。欲了解该科研站及相关科研工作的更多信息，请访问http://scottycreek.com。