Recent Warming Fuels Increased Organic Carbon Export From Arctic Permafrost

Abstract

Climate‐driven thawing of Arctic permafrost renders its vast carbon reserves susceptible to microbial degradation, serving as a potentially potent positive feedback hidden within the climate system. While seemingly intuitive, the relationship between thermally driven permafrost losses and organic carbon (OC) export remains largely unexplored in natural settings. Filling this knowledge gap, we present down‐core bulk and compound‐specific radiocarbon records of permafrost change from a sediment core taken within the Alaskan Colville River delta spanning the last c. 2,700 years. Fingerprinted by significantly older radiocarbon ages of bulk OC and long‐chain fatty acids, these data expose a thermally driven increase in permafrost OC export and/or deepening of mobilizable permafrost layers over the last c. 160 years after the Little Ice Age. Comparison of OC content and radiocarbon data between recent and Roman warming episodes likely implies that the rate of warming, alongside the prevailing boundary conditions, may dictate the ultimate fate of the Arctic's permafrost inventory. Our findings highlight the importance of leveraging geological records as archives of Arctic permafrost mobilization dynamics with temperature change.

SCALING THE 14C-EXCURSION SIGNAL IN MULTIPLE TREE-RING SERIES WITH DYNAMIC TIME WARPING

“…DTW analysis demonstrates that 14 C variance amplification at both 1052 CE and 1054 CE is caused by the impact of a single event. The inconsistent fingerprint of the 1054 CE event in time across the space may result from cross-dating nonconformity, regional (local) flux of old carbon at the northern site (Finland) due to intensified permafrost melt and ancient CO 2 release when the tree grew during the Medieval Warm Epoch (Feng et al 2013;Wild et al 2019;Zhang et al 2021) and/or large latitude gradient (e.g., Burr 2007;Büntgen et al 2018;Uusitalo et al 2018). Clearly, the 1052-1054 CE signature is a unique increase in 14 C production rate and warrants further investigation.…”