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Refined Estimates of Net Community Production in the Subarctic Northeast Pacific Derived From ΔO₂/Ar Measurements With N₂O-Based Corrections for Vertical Mixing Izett, Robert W.; Manning, Cara C.; Hamme, Roberta C.; Tortell, Philippe Daniel, 1972-
Abstract
We present the first field application of a N₂O-based approach to correct for vertical mixing in the estimation of net community production (NCP) from mixed layer O₂ measurements. Using new ship-based observations of N₂O and biological oxygen saturation anomalies (ΔO₂/Ar) from the Subarctic Northeast Pacific, we provide refined mixed layer NCP estimates across contrasting hydrographic regimes and a comprehensive assessment of the methodological considerations and limitations of the approach. Increased vertical mixing coefficients at the base of the mixed layer, derived using N₂O measurements, corresponded with periods of heightened wind speed and coastal upwelling. Corrections were most significant in coastal regions where the vertical supply of low-O₂ water can otherwise falsely imply net heterotrophy from negative ΔO₂/Ar measurements. After correcting for the mixing flux, all coastal stations showed autotrophic signatures, with maximum NCP exceeding 100 mmol O₂ m⁻² d⁻¹ in the spring and summer. Vertical fluxes were lower in off-shelf waters but often contributed more than 50% to corrected NCP. At some oceanic stations, however, the cooccurrence of N₂O minima and O₂ maxima resulted in biased (overestimated) N₂O corrections. Evaluating vertical fluxes in these regions remains a challenge for ship-based studies. Nonetheless, our refined NCP estimates show better coherence with surface chlorophyll, temperature, and mixed layer depth than uncorrected values. Potential mixed layer N₂O production introduces some uncertainty in the approach, but errors are likely to be small. Ultimately, this work provides rationale for the adoption of the N₂O correction to refine NCP estimates, particularly in coastal waters.
Item Metadata
Title |
Refined Estimates of Net Community Production in the Subarctic Northeast Pacific Derived From ΔO₂/Ar Measurements With N₂O-Based Corrections for Vertical Mixing
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Creator | |
Date Issued |
2018-03-07
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Description |
We present the first field application of a N₂O-based approach to correct for vertical mixing in the estimation of net community production (NCP) from mixed layer O₂ measurements. Using new ship-based observations of N₂O and biological oxygen saturation anomalies (ΔO₂/Ar) from the Subarctic Northeast Pacific, we provide refined mixed layer NCP estimates across contrasting hydrographic regimes and a comprehensive assessment of the methodological considerations and limitations of the approach. Increased vertical mixing coefficients at the base of the mixed layer, derived using N₂O measurements, corresponded with periods of heightened wind speed and coastal upwelling. Corrections were most significant in coastal regions where the vertical supply of low-O₂ water can otherwise falsely imply net heterotrophy from negative ΔO₂/Ar measurements. After correcting for the mixing flux, all coastal stations showed autotrophic signatures, with maximum NCP exceeding 100 mmol O₂ m⁻² d⁻¹ in the spring and summer. Vertical fluxes were lower in off-shelf waters but often contributed more than 50% to corrected NCP. At some oceanic stations, however, the cooccurrence of N₂O minima and O₂ maxima resulted in biased (overestimated) N₂O corrections. Evaluating vertical fluxes in these regions remains a challenge for ship-based studies. Nonetheless, our refined NCP estimates show better coherence with surface chlorophyll, temperature, and mixed layer depth than uncorrected values. Potential mixed layer N₂O production introduces some uncertainty in the approach, but errors are likely to be small. Ultimately, this work provides rationale for the adoption of the N₂O correction to refine NCP estimates, particularly in coastal waters.
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Genre | |
Type | |
Language |
eng
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Date Available |
2018-09-07
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0364314
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URI | |
Affiliation | |
Citation |
Izett, R. W., Manning, C. C., Hamme, R. C., & Tortell, P. D. (2018). Refined estimates of net community production in the Subarctic Northeast Pacific derived from ΔO₂/Ar measurements with N₂O-based corrections for vertical mixing. Global Biogeochemical Cycles, 32.
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Publisher DOI |
10.1002/2017GB005792
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Peer Review Status |
Reviewed
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Scholarly Level |
Faculty; Postdoctoral; Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Rights
Attribution-NonCommercial-NoDerivatives 4.0 International