1. Nitrous Oxide Dynamics in the Siberian Arctic Ocean and Vulnerability to Climate Change.
- Author
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Wild, Birgit, Ray, Nicholas E., Lett, Céline, Davies, Amelia Jane, Kirillova, Elena, Holmstrand, Henry, Klevantceva, Elizaveta, Osadchiev, Alexander, Gangnus, Ivan, Yakushev, Evgeniy, Kosmach, Denis, Dudarev, Oleg, Gustafsson, Örjan, Semiletov, Igor, and Brüchert, Volker
- Subjects
CLIMATE change ,NITROUS oxide ,TURBIDITY ,ATMOSPHERIC turbidity ,REGIONS of freshwater influence ,OZONE layer ,OZONE-depleting substances - Abstract
Nitrous oxide (N2O) is a strong greenhouse gas and stratospheric ozone‐depleting substance. Around 20% of global emissions stem from the ocean, but current estimates and future projections are uncertain due to poor spatial coverage over large areas and limited understanding of drivers of N2O dynamics. Here, we focus on the extensive and particularly data‐lean Arctic Ocean shelves north of Siberia that experience rapid warming and increasing input of land‐derived nitrogen with permafrost thaw. We combine water column N2O measurements from two expeditions with on‐board incubation of intact sediment cores to assess N2O dynamics and the impact of land‐derived nitrogen. Elevated nitrogen concentrations in water column and sediments were observed near large river mouths. Concentrations of N2O were only weakly correlated with dissolved nitrogen and turbidity, reflecting particulate matter from rivers and coastal erosion, and correlations varied between river plumes. Surface water N2O concentrations were on average close to equilibrium with the atmosphere, but varied widely (N2O saturation 38%–180%), indicating strong local N2O sources and sinks. Water column N2O profiles and low sediment‐water N2O fluxes do not support strong sedimentary sources or sinks. We suggest that N2O dynamics in the region are influenced by water column N2O consumption under aerobic conditions or in anoxic microsites of particles, and possibly also by water column N2O production. Changes in biogeochemical and physical conditions will likely alter N2O dynamics in the Siberian Arctic Ocean over the coming decades, in addition to reduced N2O solubility in a warmer ocean. Plain Language Summary: Nitrous oxide (N2O) is a strong greenhouse gas and can reduce the stratospheric ozone layer. Around 20% of global N2O emissions come from the ocean. These estimates are uncertain due to scarce data from large areas and a limited understanding of controls on N2O production and consumption. Here, we focus on the shallow but large continental shelves of the Arctic Ocean north of Siberia. This area is rapidly warming, and receives land‐derived nitrogen from rivers and coastal erosion that is expected to increase with permafrost thaw. We analyzed N2O concentrations in the water column during two expeditions, and performed incubations with intact sediment cores to measure N2O release from sediment to water. Our data show that concentrations of dissolved nitrogen in the water and of total nitrogen in sediments increase toward large river mouths. Concentrations of N2O were weakly correlated with a range of parameters including dissolved inorganic nitrogen and turbidity, with high variability among river plumes. On average, water‐air N2O fluxes were low, but strong N2O sources and sinks were observed locally. An increase in water temperature could substantially reduce N2O solubility in the ocean water, and add to biogeochemical and physical changes that could alter N2O production itself. Key Points: We studied N2O dynamics on the vast Siberian Arctic Ocean shelves that experience strong warming and nitrogen input from land permafrostN2O was variably influenced by dissolved nitrogen and turbidity from land, and likely consumed in the water columnSurface water N2O was on average in equilibrium with the atmosphere, but strong local sources and sinks were observed [ABSTRACT FROM AUTHOR]
- Published
- 2023
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