Biogeochemistry of dissolved organic matter in the Arctic permafrost and the Lena delta


Contact
Gerhard.Kattner [ at ] awi.de

Abstract

Permafrost soils have accumulated vast stores of organic carbon recently estimated to be ~1600 Pg C. During the next century, near-surface permafrost across the circumpolar Arctic is expected to degrade significantly. Large amounts, especially of dissolved organic matter (DOM), may be released, transported to the oceans and either mineralized or convected down to the deep Arctic Ocean. Although DOC in Arctic rivers often shows relatively conservative characteristics, it has been recently shown that terrestrial DOC removal is an active but probably slow process. The major discharge of freshwater to the Arctic Ocean occurs within a very short period of time when ice is melting in late spring /early summer. All involved processes are characterized by high spatial and temporal variability but in their entirety they are likely to have critical implications for primary production and carbon cycling on Arctic shelves and in the Arctic Ocean. DOC in the Lena River has quite similar concentrations over long distances with a high carbon to nitrogen ratio. The classical relation between DOC and salinity in the coastal regions implies a conservative mixing, however, a strong modification of DOM must occur during transition from freshwater to seawater. C:N ratio strongly decrease in the estuarine and near shore regions. The discharge of nutrients is low except for silicate. The major aim is to identify and quantify the flux of soil-derived DOM and nutrients from the permafrost into the Lena estuary and the Arctic shelf-ocean system. Field sampling and experiments were carried out in August 2009 and 2010. Samples were taken from the main channels in the Lena delta and some near-shore coastal stations in the Buor-Khaya Bay as well as from run-off water from different ice complexes and permafrost lakes and soils. These samples with very different characteristics had highly variable DOC concentrations that are in the range from 450 to 650 µM for Lena River water, 800 to 10,800 µM for ice complex meltwater and of about 800 µM for the ice of ice complexes. Most of the freshwater and DOM is discharged via the eastern and north-eastern channels of the Lena River. Bacterial and photo-degradation batch experiments have shown that a considerable amount of terrestrial DOM of ice complex meltwater is mineralized or degraded. Ultra high resolution mass spectrometry is used to identify markers to trace the fate of DOM. Our goal is to implement a molecular classification system for the bioavailability of permafrost-derived DOM.



Item Type
Conference (Poster)
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Divisions
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Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
SOM-5 5th International Workshop on Soil and Sedimentary Organic Matter Stabilization and Destabilization, 07 Oct 2012 - 11 Oct 2012, Ascona, Switzerland.
Eprint ID
31531
Cite as
Kattner, G. , Koch, B. , Flerus, R. and Dubinenkov, I. (2012): Biogeochemistry of dissolved organic matter in the Arctic permafrost and the Lena delta , SOM-5 5th International Workshop on Soil and Sedimentary Organic Matter Stabilization and Destabilization, Ascona, Switzerland, 7 October 2012 - 11 October 2012 .


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