Rapid expansion of fixed nitrogen deficit in the eastern Pacific Ocean revealed by 50 year time series

Evans, Natalya; Tichota, Juliana; Ruef, Wendi; Moffett, James W.; Devol, Allan H.

doi:10.1002/essoar.10512279.2

Cited by 1 publication

(5 citation statements)

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“…This atlas reveals that the 110°W line crosses through some of the most permanently oxygen deficient waters. Data from these eight cruises have been uploaded to Zenodo (https://doi.org/10.5281/zenodo.6519188, Evans et al., 2022a).…”

Section: Methodsmentioning

confidence: 99%

“…(2019) with data shared by the author and contour lines added by eye (Figure 1). The data and code for these analyses are included in the appropriate Zotero repositories for this paper (Evans et al., 2022a, 2022b).…”

Section: Methodsmentioning

confidence: 99%

“…eOMP analysis calculations were performed using the GUI option in a modified version of the omp2 MATLAB package written by Johannes Karstensen and Matthias Tomczak (Karstensen, 2023), which have been uploaded to Zenodo (Evans et al., 2022b). The original version of this software can be found at https://www.mathworks.com/matlabcentral/fileexchange/1334-omp-analysis.…”

Section: Methodsmentioning

confidence: 99%

“…We calculated the core oxygen deficient layer potential density by averaging the top and bottom potential densities of the ODZ specified in Kwiecinski and Babbin (2021), and we recreated a figure of water entry into the ODZ from Margolskee et al (2019) with data shared by the author and contour lines added by eye (Figure 1). The data and code for these analyses are included in the appropriate Zotero repositories for this paper (Evans et al, 2022a(Evans et al, , 2022b.…”

Section: Data Processing For Time Series Comparison'mentioning

confidence: 99%

“…This method requires that we define endmember nutrient concentrations as well as specify a stoichiometry for fixed nitrogen loss. We grounded our fixed nitrogen loss stoichiometry in the observed stoichiometry for anaerobic remineralization in the ETNP ODZ ( eOMP analysis calculations were performed using the GUI option in a modified version of the omp2 MATLAB package written by Johannes Karstensen and Matthias Tomczak (Karstensen, 2023), which have been uploaded to Zenodo (Evans et al, 2022b). The original version of this software can be found at https://www.mathworks.…”

Section: Fixed Nitrogen Loss Via Water Mass Analysismentioning

confidence: 99%

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Rapid Expansion of Fixed Nitrogen Deficit in the Eastern Pacific Ocean Revealed by 50‐Year Time Series

Evans,

Tichota,

Ruef

et al. 2023

Global Biogeochemical Cycles

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Climate change is expected to increase the strength of ocean Oxygen Deficient Zones (ODZs), but we lack detailed understanding of the temporal or spatial variability of these ODZs. A fifty‐year time series in the Eastern Tropical North Pacific (ETNP) ODZ revealed that it has strengthened by 30% from 1994‐2019. We subdivided the ODZ into a core and a deep layer based on potential density and revealed that different processes control the magnitude of fixed nitrogen loss between these regions. We postulate that the depth of the upper ETNP ODZ water mass, the 13 ºC Water, influences the organic carbon supply to the core ODZ and therefore its strength. We correlated the maximum fixed nitrogen loss in the core ODZ with a nearby sedimentary nitrogen isotope record and found that this recent increase in fixed nitrogen loss has only occurred a few times over the last 1,200 years. Using this correlation, we derived the first confidence interval for the natural variability of the maximum fixed nitrogen loss within the ETNP ODZ, which has a range of 3.3 µmol kg‐1 (p=0.01). While the current increase is only comparable to two previous events, it is within the confidence interval for natural variability (p=0.03). The deep ODZ also strengthened from 2016‐2019 by approximately 30%, but this increase occurred more rapidly than the core ODZ, and this dramatic increase was not observed over the rest of the 40 years. Climate‐driven intensification could lead to unprecedented changes in the ETNP ODZ within the next decade.

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Section: Methodsmentioning

confidence: 99%