Feen
Melanie L.
Feen
Melanie L.
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PreprintAir calibration of an oxygen optode on an underwater glider( 2017-02) Nicholson, David P. ; Feen, Melanie L.An Aanderaa Data Instruments 4831 Oxygen optode was configured on an underwater glider such that the optode extended into the atmosphere during each glider surface interval enabling in situ calibration of the sensor by directly measuring the known partial pressure of the atmosphere. The approach, which has previously been implemented on profiling floats but not on gliders, was tested during a 15-day deployment at the New England shelf break in June 2016, a productive period during which surface O2 saturation averaged 110%. Results were validated by shipboard Winkler O2 calibration casts, which were used to determine a sensor gain factor of 1.055 ± 0.004. Consistent with profiling float observations, air measurements contain contamination from splashing water and/or residual seawater on the sensor face. Glider surface measurements were determined to be a linear combination of 36% of surface water and 64% atmospheric air. When correcting air measurements for this effect, a sensor gain correction of 1.055 ± 0.005 was calculated based on comparing glider air measurements to the expected atmospheric pO2 calculated from atmospheric pressure and humidity data from a nearby NOAA buoy. Thus, the two approaches were in agreement and were both demonstrated to be accurate to within ±0.5%. We expect uncertainty in the air-calibration could be further reduced by increasing the vertical positioning of the optode, lengthening deployment time, or operating in waters with surface O2 saturation closer to equilibrium.
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ArticleEvaluation of new and net community production estimates by multiple ship-based and autonomous observations in the Northeast Pacific Ocean(University of California Press, 2023-06-16) Niebergall, Alexandria K. ; Traylor, Shawnee ; Huang, Yibin ; Feen, Melanie ; Meyer, Meredith G. ; McNair, Heather M. ; Nicholson, David P. ; Fassbender, Andrea J. ; Omand, Melissa M. ; Marchetti, Adrian ; Menden-Deuer, Susanne ; Tang, Weiyi ; Gong, Weida ; Tortell, Philippe D. ; Hamme, Roberta C. ; Cassar, NicolasNew production (NP) and net community production (NCP) measurements are often used as estimates of carbon export potential from the mixed layer of the ocean, an important process in the regulation of global climate. Diverse methods can be used to measure NP and NCP, from research vessels, autonomous platforms, and remote sensing, each with its own set of benefits and uncertainties. The various methods are rarely applied simultaneously in a single location, limiting our ability for direct comparisons of the resulting measurements. In this study, we evaluated NP and NCP from thirteen independent datasets collected via in situ, in vitro, and satellite-based methods near Ocean Station Papa during the 2018 Northeast Pacific field campaign of the NASA project EXport Processes in the Ocean from RemoTe Sensing (EXPORTS). Altogether, the datasets indicate that carbon export potential was relatively low (median daily averages between −5.1 and 12.6 mmol C m−2 d−1), with most measurements indicating slight net autotrophy in the region. This result is consistent with NCP estimates based on satellite measurements of sea surface temperature and chlorophyll a. We explored possible causes of discrepancies among methods, including differences in assumptions about stoichiometry, vertical integration, total volume sampled, and the spatiotemporal extent considered. Results of a generalized additive mixed model indicate that the spatial variation across platforms can explain much of the difference among methods. Once spatial variation and temporal autocorrelation are considered, a variety of methods can provide consistent estimates of NP and NCP, leveraging the strengths of each approach.