TY - JOUR
T1 - Linkages Among Climate, Fire, and Thermoerosion in Alaskan Tundra Over the Past Three Millennia
AU - Chipman, M. L.
AU - Hu, F. S.
N1 - Funding Information:
All data reported here are available at http://www.ncdc.noaa.gov/paleo/data. html and in the supporting information. Funding for this research was provided by the NSF (ARC-1023477 to F. S. H). M. L. C. was supported by the EPA Science to Achieve Results Fellowship and a USDA Cooperative State Research, Education, and Extension Service grant (ILLU 875-952). We thank R. Kelly, P.E. Higuera, and A. Young for field assis tance, A. Lingwall, T. Brown, and R. Vachula for sediment analyses, and D. Colombaroli and an anonymous reviewer for constructive comments.
Publisher Copyright:
©2017. American Geophysical Union. All Rights Reserved.
PY - 2017/12
Y1 - 2017/12
N2 - Amplified Arctic warming may facilitate novel tundra disturbance regimes, as suggested by recent increases in the rate and extent of thermoerosion and fires in some tundra areas. Thermoerosion and wildfire can exacerbate warming by releasing large permafrost carbon stocks, and interactions between disturbance regimes can lead to complex ecosystem feedbacks. We conducted geochemical and charcoal analyses of lake sediments from an Alaskan lake to identify thermoerosion and fire events over the past 3,000 years. Thermoerosion was inferred from lake sediments in the context of modern soil data from retrogressive thaw slumps (RTS). Magnetic susceptibility (MS), Ca:K, and Ca:Sr increased with depth in modern RTS soils and were higher on recently exposed than older slump surfaces. Peaks in bulk density, % CaCO3, Ca:K, Ca:Sr, and MS values in the sediments suggest at least 18 thermoerosion events in the Loon Lake watershed over the past 3,000 years. Charcoal analysis identifies 22 fires over the same period at this site. Temporal variability in these records suggests climate-driven responses of both thermoerosion and fire disturbance regimes, with fewer RTS episodes and fire events during the Little Ice Age than the Medieval Climate Anomaly. Moreover, RTS activity lagged behind catchment fires by 20–30 years (>90% confidence interval), implying that fires facilitated thermoerosion on decadal time scales, possibly because of prolonged active-layer deepening following fire and postfire proliferation of insulative shrub cover. These results highlight the potential for complex interactions between climate, vegetation, and tundra disturbance in response to ongoing warming.
AB - Amplified Arctic warming may facilitate novel tundra disturbance regimes, as suggested by recent increases in the rate and extent of thermoerosion and fires in some tundra areas. Thermoerosion and wildfire can exacerbate warming by releasing large permafrost carbon stocks, and interactions between disturbance regimes can lead to complex ecosystem feedbacks. We conducted geochemical and charcoal analyses of lake sediments from an Alaskan lake to identify thermoerosion and fire events over the past 3,000 years. Thermoerosion was inferred from lake sediments in the context of modern soil data from retrogressive thaw slumps (RTS). Magnetic susceptibility (MS), Ca:K, and Ca:Sr increased with depth in modern RTS soils and were higher on recently exposed than older slump surfaces. Peaks in bulk density, % CaCO3, Ca:K, Ca:Sr, and MS values in the sediments suggest at least 18 thermoerosion events in the Loon Lake watershed over the past 3,000 years. Charcoal analysis identifies 22 fires over the same period at this site. Temporal variability in these records suggests climate-driven responses of both thermoerosion and fire disturbance regimes, with fewer RTS episodes and fire events during the Little Ice Age than the Medieval Climate Anomaly. Moreover, RTS activity lagged behind catchment fires by 20–30 years (>90% confidence interval), implying that fires facilitated thermoerosion on decadal time scales, possibly because of prolonged active-layer deepening following fire and postfire proliferation of insulative shrub cover. These results highlight the potential for complex interactions between climate, vegetation, and tundra disturbance in response to ongoing warming.
KW - Noatak National Preserve
KW - paleoecology
KW - retrogressive thaw slump
KW - thermoerosion
KW - tundra disturbance
KW - wildfire
UR - http://www.scopus.com/inward/record.url?scp=85039546528&partnerID=8YFLogxK
U2 - 10.1002/2017JG004027
DO - 10.1002/2017JG004027
M3 - Article
AN - SCOPUS:85039546528
SN - 2169-8953
VL - 122
SP - 3362
EP - 3377
JO - Journal of Geophysical Research: Biogeosciences
JF - Journal of Geophysical Research: Biogeosciences
IS - 12
ER -