New Insights Test our Fundamental Understanding of How Thermokarst Influences Permafrost Peatlands
Abstract
Permafrost thaw and release of greenhouse gases through enhanced microbial activity is considered one of the most likely biogeochemical feedbacks to the future climate system. Most 'permafrost-enabled' Earth System models agree that permafrost carbon release is likely to be significant enough to include in emissions negotiations. Yet to date most models simulate only top-down thaw and do not represent lateral or abrupt thaw processes that can lead to subsidence and ecosystem state changes. Recent empirical and modeling studies have revealed surprising insights into how thermokarst develops in permafrost peatlands and what this means for carbon storage. Regional-scale sampling (100+ km) across gradients of time-since-thaw shows that permafrost ontogeny (epigenetic versus syngenetic permafrost) influences the vulnerability of thawing permafrost carbon to mineralization and release. At a landscape scale (10+ km), we tested whether there are predictable relationships between initiation date (age of a thermokarst feature) and surface area in several ecoregions of Alaska. We found no consistent size-age relationships, complicating our ability to simulate thermokarst development through space and time. We further tested subsurface and geomorphic properties as predictors of permafrost vulnerability or resistance to abrupt thaw. At local scales (10-50 m), our results have previously shown that methane hotspots occur at the edges of thermokarst bogs due to rapid turnover of newly thawed permafrost carbon. However, our recent results show that these patterns of methane emissions are controlled more by the timing of rainfall and its influence on hydrology and deep soil temperatures than the timing of permafrost thaw. Overall, our results are testing our fundamental understanding of thermokarst initiation, development, and behavior, which is relevant for how models might start to incorporate abrupt thaw into their frameworks.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B22D..06T
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 0702 Permafrost;
- CRYOSPHEREDE: 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE