Arctic and Boreal Carbon Stocks and Vulnerability
Abstract
A newly enlarged soil carbon database with an order of magnitude more numerous deep sampling sites has verified the widespread pattern of large quantities of organic carbon accumulated deep in permafrost (perennially frozen) zone soils. The known pool of permafrost carbon across the northern circumpolar permafrost zone is now estimated to be 1330-1580 Pg carbon, with the potential for an additional 400 Pg carbon in deep permafrost sediments that remain largely unquantified. New work has also sharpened our understanding of carbon pools in the Yedoma region, portion of Siberia and Alaska that remained ice-free during the last glacial period. These soils accumulated carbon as permafrost formed during glacial periods, but some of that initial C thawed as a result of landscape processes, in particular lake formation, which altered the distribution of permafrost. The current Yedoma region, comprising permafrost from the last glacial period together with thaw features that accumulated additional C before becoming frozen again, together contains several hundred Pg C in deep (> 1m) soils. A more comprehensive understanding of these landscape processes causing permafrost to thaw abruptly has shown that upland and lowland landscapes are susceptible to abrupt thaw and that this process is likely to be an important mechanism as permafrost thaws in a warming climate. Large-scale models for the most part do not yet incorporate abrupt thaw mechanisms, but can simulate direct climate warming effects on ecosystem carbon balance. Model projections tend to estimate losses of carbon in line with empirical measurements, but differ in the extent that they project that soil carbon loss will be compensated by new plant growth and carbon input to the surface soil. Together, the loss of carbon from thawing permafrost soils and disturbance by fire in combination with offsetting plant uptake response determines the net effect of high latitudes on the carbon cycle of both North America and the globe.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMGC23K..10S
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGEDE: 4806 Carbon cycling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL