Nitrous oxide in the Southwest Indian Ocean

Arévalo-Martínez, Damian L., Xiao, Ma, Eirund, Gesa K. and Bange, Hermann W. (2017) Nitrous oxide in the Southwest Indian Ocean [Talk] In: Good Hope for Earth Science - 2017 Joint IAPSO-IAMAS-IAGA Assembly, 27.08.-01.09.2017, Cape Town, South Africa.

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Abstract

The southwestern basin of the Indian Ocean (SWIO) remains a rather under-sampled region with regards to nitrogen cycle processes. Here we present the results of extensive surface and water column nitrous oxide (N2O) measurements as well as the first reported open ocean measurements of hydroxylamine (NH2OH). Wind-driven upwelling in the zonal band between 5°S and 10°S led to an enhanced efflux of N2O to the atmosphere with saturation values up to 122% and a maximum sea-to-air flux of 2.3 nmol m-2 s-1. N2O depth profiles showed supersaturation conditions throughout the water column with a distinct maximum (~ 30 nmol L-1) at about 1000 m. Excess N2O (ΔN2O) was positively correlated with apparent oxygen utilization (AOU) and nitrate concentrations although different slopes of the ΔN2O/AOU relationships could be identified above and below the concentration maxima. Although the vertical distribution of NH2OH was highly variable, combined analysis with N2O and nutrient data suggests nitrification as the major formation pathway of N2O in the SWIO. Our observations suggest that the SWIO is a rather weak, yet, perennial source of atmospheric N2O which should be considered in future efforts aiming to long-term monitoring of greenhouse gases in the Indian Ocean.

Document Type: Conference or Workshop Item (Talk)
Keywords: Nitrous oxide Hydroxylamine Trace gases Indian Ocean Open ocean upwelling
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > The Future Ocean - Cluster of Excellence
Projects: InGOS, SOPRAN, Future Ocean
Expeditions/Models:
Date Deposited: 20 Sep 2017 09:14
Last Modified: 07 Jan 2019 07:15
URI: http://eprints.uni-kiel.de/id/eprint/39455

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