BUSCADOR RECOLECTA

Poster.-- 8th hybrid SOLAS Open Science Conference, hosted by the University of Cape Town, South Africa, 25 - 29 September 2022, Although greenhouse gases occur naturally in the atmosphere, their concentration has increased since 1850 due to anthropogenic activities. The contribution of the marine domains to carbon dioxide (CO2) uptake from the atmosphere has been computed and periodically re-evaluated given the implications for climate change. However, the fate of atmospheric nitrous oxide (N2O) had not been considered until recently. We evaluated the amount of N2O of anthropogenic origin (N2Oant) taken up by the global ocean. The oceanic inventory of N2Oant has been calculated through a novel method, that considers the direct proportionality existing between the excess of both N2O and CO2 in the atmosphere since 1850. Applying this relationship to different versions of Cant climatology, we obtained the oceanic global distribution and inventories of N2Oant. The oceanic uptake of N2Oant from pre-industrial times is 10.2±1.0 Tg-N, which is comparable to others terms of global N2O inventories, such as oceanic N deposition, No

16 pages, 1 table, 8 figures, Since 1800, the concentration of greenhouse gases like nitrous oxide (N2O) and carbon dioxide (CO2) has significantly increased due to anthropogenic activities. Oceanic anthropogenic CO2 (Cant) uptake from the atmosphere has been quantified and periodically re-evaluated given the implications for climate change. However, the potential oceanic uptake of N2O has been largely overlooked. This study quantifies the uptake of N2O of anthropogenic origin (N2Oant) taken up by the global ocean and how it relates with the anthropogenic CO2. The oceanic inventory of N2Oant has been quantified using two approaches which consider the anthropogenic perturbation of N2O and CO2 as conservative tracers: first, a direct approach using the Transient Time Distribution (TTD) method; and second, indirectly through a novel method, founded on the direct proportionality between the excess of both N2O and CO2 in the atmosphere since 1800. Our results show that the North Atlantic Ocean is a key region of maximum accumulation of N2Oant due to the confluence of cold and ventilated waters. The global oceanic uptake of N2Oant from the pre-industrial times to 2010 was estimated to be 11.5 ± 2.3 Tg-N, with an annual uptake rate of 0.23 ± 0.05 Tg-N yr−1. The study shows that oceanic sequestration contributes to a small portion of global N2O inventories, but it is comparable to other N2O oceanic budget numbers derived from atmospheric nitrogen deposition. Furthermore, connecting the N2Oant and Cant oceanic distributions is a valuable tool for linking the perturbation of the Anthropocene on the N and C cycles in the ocean, AV and FFP were supported by the BOCATS2 (PID2019-104279GB-C21) project funded by MICIU/AEI/10.13039/501100011033 and by European Union under Grant agreement no. 101094690 (EuroGO-SHIP). In addition, M de la Paz was also supported by a contract financed by the Spanish Ministry of Science PTA2019–017983-I. “This work is also a contribution to OCEANS + CSIC PTI efforts.”, Peer reviewed

8 files, Dataset of "The Unaccounted Oceanic Sink of Anthropogenic Nitrous Oxide and its Relationship with Anthropogenic Carbon Dioxide" Following files are provided: - column_inventory_cant_molm2_n2oant_mmolm2.csv: Stands for the integrated values of Cant and N2Oant for each method and for the full water column in the WOA 1deg x 1deg grid - 3D_global_inventory_cant_n2oant.nc: Stands for the concentration values of Cant and N2Oant for each method and for the full WOA 1deg x 1deg x 33 levels grid - TTD_ files: mat files for cant and n2oant for the Glodapv2 (2016) dataset, and for Atlantic, Pacific and Indian Ocean, Agencia Estatal de Investigación, BOCATS2, funded by MICIU/AEI/10.13039/501100011033, PID2019‐104279GB‐C21; Agencia Estatal de Investigación, PTA 2019 funded by MCIN/AEI/10.13039/501100011033 PTA2019-017983-I; European Commission, Euro GO-SHIP – Euro GO-SHIP: developing a Research Infrastructure concept to support European hydrography, Peer reviewed