Max Planck Institute for Biogeochemistry, Jena, Germany.
Korea Polar Research Institute, Incheon, South Korea.
Glob Chang Biol. 2019 Oct;25(10):3254-3266. doi: 10.1111/gcb.14744. Epub 2019 Jul 24.
The sustainability of the vast Arctic permafrost carbon pool under climate change is of paramount importance for global climate trajectories. Accurate climate change forecasts, therefore, depend on a reliable representation of mechanisms governing Arctic carbon cycle processes, but this task is complicated by the complex interaction of multiple controls on Arctic ecosystem changes, linked through both positive and negative feedbacks. As a primary example, predicted Arctic warming can be substantially influenced by shifts in hydrologic regimes, linked to, for example, altered precipitation patterns or changes in topography following permafrost degradation. This study presents observational evidence how severe drainage, a scenario that may affect large Arctic areas with ice-rich permafrost soils under future climate change, affects biogeochemical and biogeophysical processes within an Arctic floodplain. Our in situ data demonstrate reduced carbon losses and transfer of sensible heat to the atmosphere, and effects linked to drainage-induced long-term shifts in vegetation communities and soil thermal regimes largely counterbalanced the immediate drainage impact. Moreover, higher surface albedo in combination with low thermal conductivity cooled the permafrost soils. Accordingly, long-term drainage effects linked to warming-induced permafrost degradation hold the potential to alleviate positive feedbacks between permafrost carbon and Arctic warming, and to slow down permafrost degradation. Self-stabilizing effects associated with ecosystem disturbance such as these drainage impacts are a key factor for predicting future feedbacks between Arctic permafrost and climate change, and, thus, neglect of these mechanisms will exaggerate the impacts of Arctic change on future global climate projections.
在气候变化下，庞大的北极永冻土碳库的可持续性对全球气候轨迹至关重要。因此，准确的气候变化预测取决于对控制北极碳循环过程的机制的可靠表述，但由于控制北极生态系统变化的多个因素的复杂相互作用，这一任务变得复杂，这些因素通过正反馈和负反馈相互关联。例如，预测的北极变暖可以受到水文状况变化的显著影响，这些变化与降水模式的改变或永久冻土退化后地形的变化有关。本研究提供了观测证据，表明在未来气候变化下，严重排水这种可能影响富含永久冻土土壤的大面积北极地区的情景，如何影响北极洪泛平原内的生物地球化学和生物地球物理过程。我们的现场数据表明，碳损失减少，感热向大气转移减少，与排水引起的植被群落和土壤热状况的长期变化有关的影响在很大程度上抵消了排水的直接影响。此外，较高的地表反照率和较低的热导率使永久冻土冷却。因此，与变暖引起的永久冻土退化有关的长期排水效应有可能缓解永久冻土碳与北极变暖之间的正反馈，并减缓永久冻土退化。像这种排水影响这样的生态系统干扰所带来的自我稳定效应是预测北极永久冻土与气候变化之间未来反馈的关键因素，因此，忽视这些机制将夸大北极变化对未来全球气候预测的影响。
