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A landscape perspective of Holocene organic carbon cycling in coastal SW Greenland lake-catchments

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journal contribution
posted on 26.10.2018 by Nicholas John Anderson, Melanie J. Leng, Christopher L. Osburn, Sherilyn C. Fritz, Antonia C. Law, Suzanne McGowan
Arctic organic carbon (OC) stores are substantial and have accumulated over millennia as a function of changes in climate and terrestrial vegetation. Arctic lakes are also important components of the regional C-cycle as they are sites of OC production and CO2emissions but also store large amounts of OC in their sediments. This sediment OC pool is a mixture derived from terrestrial and aquatic sources, and sediment cores can therefore provide a long-term record of the changing interactions between lakes and their catchments in terms of nutrient and C transfer. Sediment carbon isotope composition (δ13C), C/N ratio and organic C accumulation rates (C AR) of14C-dated cores covering the last ∼10,000 years from six lakes close to Sisimiut (SW Greenland) are used to determine the extent to which OC dynamics reflect climate relative to lake or catchment characteristics. Sediment δ13C ranges from −19 to −32‰ across all lakes, while C/N ratios are <8 to >20 (mean = 12), values that indicate a high proportion of the organic matter is from autochthonous production but with a variable terrestrial component. Temporal trends in δ13C are variable among lakes, with neighbouring lakes showing contrasting profiles, indicative of site-specific OC processing. The response of an individual lake reflects its morphometry (which influences benthic primary production), the catchment:lake ratio, and catchment relief, lakes with steeper catchments sequester more carbon. The multi-site, landscape approach used here highlights the complex response of individual lakes to climate and catchment disturbance, but broad generalisations are possible. Regional Neoglacial cooling (from ∼5000 cal yr BP) influenced the lateral transfer of terrestrial OC to lakes, with three lakes showing clear increases in OC accumulation rate. The lakes likely switched from being autotrophic (i.e. net ecosystem production > ecosystem respiration) in the early Holocene to being heterotrophic after 5000 cal yr BP as terrestrial OC transfer increased.

Funding

This work was funded in part by NERC: via support for the stable isotope facility at the BGS, research grants NE/J021474/1 and NE/K000349/1 to NJA and NERC Radiocarbon allocations 1403.0409 and 1242.1007 to SMcG. A University of Nottingham New Lecturer's Fund award to SMcG is also acknowledged. Core collection and geochemical analyses from SS49 were funded by an NSF award (V ATM-0081226) to SCF.

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  • Social Sciences

Department

  • Geography and Environment

Published in

Quaternary Science Reviews

Citation

ANDERSON, N.J. ... et al., 2018. A landscape perspective of Holocene organic carbon cycling in coastal SW Greenland lake-catchments. Quaternary Science Reviews, 202, pp. 98-108.

Publisher

© The Authors. Published by Elsevier Ltd.

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VoR (Version of Record)

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This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/ by/4.0/

Acceptance date

04/09/2018

Publication date

2018

Notes

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

ISSN

0277-3791

Language

en

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