Abrupt thaw and its effects on permafrost carbon emissions in the Tibetan Plateau: A remote sensing and modeling perspective

Abstract

The Tibetan Plateau (TP) has the largest permafrost area in the low- and mid-latitudes. With warmer ground temperatures and ice-rich terrain, the TP permafrost is potentially more vulnerable to climate warming. Abrupt thaw induced by rapid ground ice melt and thermokarst process has become more frequent in the TP, which will likely have a large impact on the regional water and carbon exchanges. This review presents recent researches on the drivers of abrupt thaw, with a focus on the hillslope thermokarst, and advances in remote sensing and process-based modeling of abrupt thaw process and the permafrost carbon feedback in the TP, with a comparison to the Arctic studies. Ground ice content and local topography are the two main factors controlling the rate and form of abrupt thaw; however, a lack of accurate estimates of ground ice content distribution and challenges in characterizing lateral heat transfer and groundwater flows greatly limit modeling capability in representing fine-scale thermokarst processes at a regional scale. High resolution satellite remote sensing has been widely used to identify various thermokarst landforms across the TP. However, studies using multi-source remote sensing to quantify the thermokarst-induced soil volume ice and mass loss are still lacking, particularly in the TP, which are important for characterizing the permafrost carbon feedback with abrupt thaw. Integration of spatial information derived from multi-source remote sensing with process-based models will allow better characterization of abrupt thaw processes, which generally occur at scales finer than model grid cells and are difficult to parameterize for coarse-resolution global and regional models. This synthesis can inform future research on better representing abrupt thaw process not only in the TP region but extending to other permafrost areas as well.