Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change

Journal of Geophysical Research: Biogeosciences
By: , and 

Links

Abstract

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 (14C) 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 (2 ka; 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 12.9–11.7 ka). In contrast, age-offsets were higher (3.0–5.0 ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7–9.0 ka) and Bølling-Allerød periods (14.5–12.9 ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were ~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.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change
Series title Journal of Geophysical Research: Biogeosciences
DOI 10.1002/2014JG002688
Volume 119
Issue 8
Year Published 2014
Language English
Publisher American Geophysical Union
Contributing office(s) Alaska Science Center Geography
Description 22 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research: Biogeosciences
First page 1630
Last page 1651
Country United States
State Alaska