Estimates of vertical turbulent mixing used to determine a vertical gradient in net and gross oxygen production in the oligotrophic South Pacific Gyre

Haskell, William Z.; Prokopenko, Maria G.; Stanley, Rachel H. R.; Knapp, Angela N.

doi:10.1002/2016gl069523

Cited by 18 publications

(22 citation statements)

References 76 publications

(115 reference statements)

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“…This change was smaller than the rates of GOP and CR, but similar to the net O 2 production reported for the mixed layer from the O 2 /Ar saturation ratio not corrected for diapycnal fluxes (Quay et al ; Ferrón et al ). These results indicate that the surface layer can be close to metabolic balance, consistent with some previous studies from subtropical gyres in stratified conditions that suggested that the export of organic material to the mesopelagic zone is not compensated by net photosynthesis within the mixed layer (Knauer et al ; Coale and Bruland ; Haskell II et al ). To confirm this hypothesis, as well as to improve our estimate of the biogenic O 2 change, we need more precise estimates of diapycnal oxygen fluxes.…”

Section: Assessment and Discussionsupporting

confidence: 91%

The estimation of gross oxygen production and community respiration from autonomous time‐series measurements in the oligotrophic ocean

Barone

Nicholson

Ferrón

et al. 2019

Limnology & Ocean Methods

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Diel variations in oxygen concentration have been extensively used to estimate rates of photosynthesis and respiration in productive freshwater and marine ecosystems. Recent improvements in optical oxygen sensors now enable us to use the same approach to estimate metabolic rates in the oligotrophic waters that cover most of the global ocean and for measurements collected by autonomous underwater vehicles. By building on previous methods, we propose a procedure to estimate photosynthesis and respiration from vertically resolved diel measurements of oxygen concentration. This procedure involves isolating the oxygen variation due to biological processes from the variation due to physical processes, and calculating metabolic rates from biogenic oxygen changes using linear least squares analysis. We tested our method on underwater glider observations from the surface layer of the North Pacific Subtropical Gyre where we estimated rates of gross oxygen production and community respiration both averaging 1.0 mmol O2 m−3 d−1, consistent with previous estimates from the same environment. Method uncertainty was computed as the standard deviation of the fitted parameters and averaged 0.6 and 0.5 mmol O2 m−3 d−1 for oxygen production and respiration, respectively. The variability of metabolic rates was larger than this uncertainty and we were able to discern covariation in the biological production and consumption of oxygen. The proposed method resolved variability on time scales of approximately 1 week. This resolution can be improved in several ways including by measuring turbulent mixing, increasing the number of measurements in the surface ocean, and adopting a Lagrangian approach during data collection.

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Section: Assessment and Discussionsupporting

confidence: 91%

The estimation of gross oxygen production and community respiration from autonomous time‐series measurements in the oligotrophic ocean

Barone

Nicholson

Ferrón

et al. 2019

Limnology & Ocean Methods

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“…[] to calculate a 15 day weighted K z . These estimates have an uncertainty of ±34% [ Haskell et al ., ]. All upwelling velocities, piston velocities, and eddy diffusivities used in this study are reported in Table .…”

Section: Calculationsmentioning

confidence: 99%

“…Estimated eddy diffusivity due to shear at the base of the mixed layer using W 10 , O 2 , and density. Uncertainty reported as 34% [ Haskell et al ., ].…”

Section: Calculationsmentioning

confidence: 99%

Annual cyclicity in export efficiency in the inner Southern California Bight

Haskell

Prokopenko

Hammond

et al. 2017

Global Biogeochemical Cycles

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The balance of marine autotrophy and heterotrophy regulates the ocean's ability to serve as a CO2 sink, as organic material produced by autotrophs sinks into the ocean interior to drive the biological pump. Marine ecosystems over the continental margins, especially coastal upwelling regions, account for a disproportionate amount of carbon export; thus, even small fluctuations in export in these regions can have a large impact on the global carbon cycle. In this study, we estimated the rate of gross oxygen production (GOP), stoichiometrically related to gross primary production, by combining measurements of the triple isotope composition of dissolved oxygen with estimates of vertical advection, eddy diffusion, and air‐sea gas exchange in a one‐dimensional two‐box nonsteady state model of the euphotic zone. Net oxygen production (NOP) estimates based on O2/Ar were then combined with GOP to estimate the NOP/GOP ratio, or potential export efficiency, out of the euphotic zone at the San Pedro Ocean Time‐series during an 18 month period between January 2013 and June 2014. GOP estimates ranged from 161 ± 44 to 477 ± 155 mmol m−2 d−1 during this period, peaking in May each year, and NOP/GOP ratios ranged from 0.05 ± 0.10 to 0.65 ± 0.28. The highest export efficiency occurred in late February/early March, following the onset of spring upwelling, declining as the upwelling season continued. This study demonstrates that export efficiency changes through time in this temperate coastal upwelling region on a repeated annual cycle, and the magnitude of export efficiency suggests efficient photosynthetic energy conversion by phytoplankton in spring.

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“…This result is similar to estimates by Haskell et al . [] who determined K z = 1.5(0.6) × 10 −5 m 2 s −1 at the base of the mixed layer during fall and winter in the Southern California Bight, using a wind speed‐based parameterization of turbulence due to shear [ Haskell et al ., ]. The average vertical biological

O_{2}

flux was −3.5(4.6) mmol

O_{2}

m −2 d −1 , and the range was −19.0 to −0.1 mmol

O_{2}

m −2 d −1 .…”

Section: Calculationsmentioning

confidence: 99%

Impact of recently upwelled water on productivity investigated using in situ and incubation‐based methods in Monterey Bay

et al. 2017

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Photosynthetic conversion of CO2 to organic carbon and the transport of this carbon from the surface to the deep ocean is an important regulator of atmospheric CO2. To understand the controls on carbon fluxes in a productive region impacted by upwelling, we measured biological productivity via multiple methods during a cruise in Monterey Bay, California. We quantified net community production and gross primary production from measurements of O2/Ar and O2 triple isotopes ( 17Δ), respectively. We simultaneously conducted incubations measuring the uptake of 14C, 15NO3−, and 15NH4+, and nitrification, and deployed sediment traps. At the start of the cruise (Phase 1) the carbon cycle was at steady state and the estimated net community production was 35(10) and 35(8) mmol C m−2 d−1 from O2/Ar and 15N incubations, respectively, a remarkably good agreement. During Phase 1, net primary production was 96(27) mmol C m−2 d−1 from C uptake, and gross primary production was 209(17) mmol C m−2 d−1 from 17Δ. Later in the cruise (Phase 2), recently upwelled water with higher nutrient concentrations entered the study area, causing 14C and 15NO3− uptake to increase substantially. Continuous O2/Ar measurements revealed submesoscale variability in water mass structure and likely productivity in Phase 2 that was not evident from the incubations. These data demonstrate that O2/Ar and 15N incubation‐based NCP estimates can give equivalent results in an N‐limited, coastal system, when the nonsteady state O2 fluxes are negligible or can be quantified.

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Estimates of vertical turbulent mixing used to determine a vertical gradient in net and gross oxygen production in the oligotrophic South Pacific Gyre

Cited by 18 publications

References 76 publications

The estimation of gross oxygen production and community respiration from autonomous time‐series measurements in the oligotrophic ocean

The estimation of gross oxygen production and community respiration from autonomous time‐series measurements in the oligotrophic ocean

Annual cyclicity in export efficiency in the inner Southern California Bight

Impact of recently upwelled water on productivity investigated using in situ and incubation‐based methods in Monterey Bay

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