Organic Carbon and Nitrogen Stocks along a Thermokarst Lake Sequence in Arctic Alaska


Contact
Matthias.Fuchs [ at ] awi.de

Abstract

Thermokarst lake landscapes are permafrost regions, which are prone to rapid (on seasonal to decadal timescales) changes, affecting carbon and nitrogen cycles. However, there is a high degree of uncertainty related to the balance between carbon and nitrogen cycling and storage. We collected twelve permafrost soil cores from six drained thermokarst lake basins (DTLB) along a chronosequence north of Teshekpuk Lake in northern Alaska, and analyzed them for carbon and nitrogen contents. For comparison, we included three lacustrine cores from an adjacent thermokarst lake and one soil core from a non‐thermokarst affected remnant upland. This allowed to calculate the carbon and nitrogen stocks of the three primary landscape units (DTLB, lake, and upland), to reconstruct the landscape history, and to analyze the effect of thermokarst lake formation and drainage on carbon and nitrogen stocks. We show that carbon and nitrogen contents and the carbon‐nitrogen ratio are considerably lower in sediments of extant lakes than in the DTLB or upland cores indicating degradation of carbon during thermokarst lake formation. However, we found similar amounts of total carbon and nitrogen stocks due to the higher density of lacustrine sediments caused by the lack of ground‐ice compared to DTLB sediments. In addition, the radiocarbon‐based landscape chronology for the past 7,000 years reveals five successive lake stages of partially, spatially overlapping DTLBs in the study region, reflecting the dynamic nature of ice‐rich permafrost deposits. With this study, we highlight the importance to include these dynamic landscapes in future permafrost carbon feedback models.



Item Type
Article
Authors
Divisions
Primary Division
Programs
Primary Topic
Peer revision
ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
49255
DOI 10.1029/2018JG004591

Cite as
Fuchs, M. , Lenz, J. , Jock, S. , Nitze, I. , Jones, B. M. , Strauss, J. , Günther, F. and Grosse, G. (2019): Organic Carbon and Nitrogen Stocks along a Thermokarst Lake Sequence in Arctic Alaska , Journal of Geophysical Research: Biogeosciences . doi: 10.1029/2018JG004591


Share


Citation

Research Platforms
N/A

Campaigns

Funded by
info:eu-repo/grantAgreement/EC/FP7/338335


Actions
Edit Item Edit Item