Seasonal methane and carbon dioxide emissions from the coastal nearshore of the Kolyma river, Siberia.


Contact
guido.grosse [ at ] awi.de

Abstract

Arctic rivers deliver ≈11% of global river discharge into the Arctic Ocean, while this ocean represents only ≈1% of the global ocean volume. Ongoing climate warming across the Arctic, and specifically Siberia, has led to regional-scale changes in precipitation patterns, greater rates of permafrost thaw and active layer deepening, as well as enhanced riverbank and coastal erosion. Combined, these climatic and cryospheric perturbations have already resulted in increased freshwater discharge and changes to constituent loads (e.g. dissolved organic carbon - OC) supplied from land to the Arctic Ocean. To date, the majority of studies examining terrestrial organic matter (OM) delivery to the Arctic Ocean have focused almost entirely on freshwater (riverine) or fully-marine environments and been conducted during late summer seasons – often due to logistical constraints. Despite this, an improved understanding of how OC is transformed, mineralised and released during transit through the highly reactive nearshore estuarine environment is critical for examining the fate and influence of terrestrial OM on the Arctic Ocean. Capturing seasonality over the open water period is also necessary to identify current OM fluxes to the ocean vs the atmosphere, and aid in constraining how future changes may modify them. Here we focus upon carbon dioxide (CO2) and methane (CH4) measurements collected during six repeated transects of the Kolyma River and nearshore zone (covering ~120 km) from 2019. Transects spanned almost the entirety of the riverine open water season (June to September). We use these results, in parallel with gas concentrations derived from prior studies, to develop and validate a simple box-model of gas emissions from the nearshore zone. Observations and model‐derived output data reveal that more than 50% of the cumulative gross delivery of CH4 and CO2 to the coastal ocean occurred during the freshet period with dissolved CH4 concentrations in surface water reaching 660 Nanomole per liter [nmol/l]. These results demonstrate the relevance of seasonal dynamics and its spatial variability which are needed in order to estimate greenhouse gas fluxes on an annual basis. More accurate understanding of land-ocean carbon fluxes in the Arctic is therefore crucial to mitigate the effects of climate change and to support the decisions of policy makers.



Item Type
Conference (Talk)
Authors
Divisions
Primary Division
Programs
Primary Topic
Helmholtz Cross Cutting Activity (2021-2027)
N/A
Peer revision
Not peer-reviewed
Publication Status
Published
Event Details
EGU General Assembly 2021, 19 Apr 2021 - 30 Apr 2021, Online.
Eprint ID
55329
DOI 10.5194/egusphere-egu21-9535

Cite as
Palmtag, J. , Manning, C. , Bedington, M. , Fuchs, M. , Göckede, M. , Grosse, G. , Juhls, B. , Lefebvre, P. , Mollenhauer, G. , Ogneva, O. , Overduin, P. , Polimene, L. , Strauss, J. , Torres, R. , Zimov, N. and Mann, P. (2021): Seasonal methane and carbon dioxide emissions from the coastal nearshore of the Kolyma river, Siberia. , EGU General Assembly 2021, Online, 19 April 2021 - 30 April 2021 . doi: 10.5194/egusphere-egu21-9535


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Arctic Land Expeditions > RU-Land_2019_Cherskiy
Arctic Land Expeditions > RU-Land_2019_Lena


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