期刊
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 119, 期 8, 页码 1630-1651出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2014JG002688
关键词
radiocarbon; lake sediment; carbon cycling; permafrost; paleoclimatology; Younger Dryas
资金
- Climate Change Program of the Bureau of Land Management
- NOSAMS 14C facility
- National Science Foundation [ARC-0902169]
- National Park Service
- UAF Center for Global Change Student Research Grant
- UAF Center for Global Change
- U.S. Geological Survey Youth Initiative Fund
- Land Change Science program
Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon age-offsets (C-14) between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost OC release over the last 14,500 years. The lake traps and archives OC imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age-offsets. Today, the age-offset (2ka; thousand of calibrated years before A.D. 1950) and the depositional rate of ancient OC from the watershed into the lake are relatively low and similar to those during the Younger Dryas cold interval (occurring 12.9-11.7ka). In contrast, age-offsets were higher (3.0-5.0ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7-9.0ka) and BOlling-AllerOd periods (14.5-12.9ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were similar to 10 times greater than today. Although permafrost OC was vulnerable to climate warming in the past, we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release. As a result, the temperature threshold to trigger widespread permafrost OC release is higher than during previous warming events.
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