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Expansion of denitrification and anoxia in the eastern tropical North Pacific from 1972 to 2012

Author(s): Horak, Rachel EA; Ruef, Wendi; Ward, Bess B; Devol, Allan H

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Abstract: The eastern tropical North Pacific (ETNP) is a large region of anoxic water that hosts widespread water column N loss (denitrification). There is some disagreement about the long‐term trends of denitrification and anoxia and long‐term studies of water column denitrification within the anoxic zone are lacking. In this study, we compared ETNP water column nitrite, N*, and O2 data along the same transect for four studies ranging from 1972 to 2012. Anoxic water volume increased, and low‐oxygen conditions expanded into shallower isopycnals from 1972 to 2012. A geochemical marker for cumulative N loss indicates that denitrification was highest in 2012 and the upper oxygen‐deficient zone (ODZ) experienced the most change. Oxygen and N loss changes in the world's largest ODZ for 2012 could not be explained by the Pacific Decadal Oscillation, and decreased O2 in supply currents and increased wind‐driven upwelling are likely mechanisms contributing to increased N loss and anoxia.
Publication Date: 14-May-2016
Citation: Horak, Rachel E.A., Wendi Ruef, Bess B. Ward, and Allan H. Devol. "Expansion of denitrification and anoxia in the eastern tropical North Pacific from 1972 to 2012." Geophysical Research Letters 43, no. 10 (2016): 5252-5260. doi:10.1002/2016GL068871.
DOI: doi:10.1002/2016GL068871
ISSN: 0094-8276
EISSN: 1944-8007
Pages: 5252 - 5260
Type of Material: Journal Article
Journal/Proceeding Title: Geophysical Research Letters
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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