Norwegian Sea net community production estimated from O2 and prototype CO2 optode measurements on a Seaglider

Possenti, Luca, Skjelvan, Ingunn, Atamanchuk, Dariia, Tengberg, Anders, Humphreys, Matthew P., Loucaides, Socratis, Fernand, Liam and Kaiser, Jan ORCID: (2021) Norwegian Sea net community production estimated from O2 and prototype CO2 optode measurements on a Seaglider. Ocean Science, 17 (2). pp. 593-614. ISSN 1812-0784

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We report on a pilot study using a CO2 optode deployed on a Seaglider in the Norwegian Sea from March to October 2014. The optode measurements required drift and lag correction and in situ calibration using discrete wa ter samples collected in the vicinity. We found that the op tode signal correlated better with the concentration of CO2, c(CO2), than with its partial pressure, p(CO2). Using the calibrated c(CO2) and a regional parameterisation of to tal alkalinity (AT) as a function of temperature and salin ity, we calculated total dissolved inorganic carbon content, c(DIC), which had a standard deviation of 11 μmol kg-2 compared with in situ measurements. The glider was also equipped with an oxygen (O2) optode. The O2 optode was drift corrected and calibrated using a c(O2) climatology for deep samples. The calibrated data enabled the calcu lation of DIC-and O2-based net community production, N(DIC) and N(O2). To derive N, DIC and O2 inventory changes over time were combined with estimates of air sea gas exchange, diapycnal mixing and entrainment of deeper waters. Glider-based observations captured two periods of increased Chl a inventory in late spring (May) and a second one in summer (June). For the May period, we found N(DIC) = (21±5) mmol m-2 d-1 , N(O2) = (94± 16) mmol m-2 d-1 and an (uncalibrated) Chl a peak con centration of craw(Chl a) = 3 mg m-3. During the June pe riod, craw(Chl a) increased to a summer maximum of 4 mg m-3 , associated with N(DIC) = (85±5) mmol m-2 d-1 and N(O2) = (126±25) mmol m-2 d -1. The high-resolution dataset allowed for quantification of the changes in N be fore, during and after the periods of increased Chl a inven tory. After the May period, the remineralisation of the mate rial produced during the period of increased Chl a inventory decreased N(DIC) to (-3 ± 5) mmol m-2 d-1 and N(O2) to (0 ± 2) mmol m-2 d-1 . The survey area was a source of O2 and a sink of CO2 for most of the summer. The deployment captured two different surface waters influenced by the Nor wegian Atlantic Current (NwAC) and the Norwegian Coastal Current (NCC). The NCC was characterised by lower c(O2) and c (DIC) than the NwAC, as well as lower N(O2) and craw(Chl a) but higher N(DIC). Our results show the poten tial of glider data to simultaneously capture time-and depth resolved variability in DIC and O2 concentrations.

Item Type: Article
Uncontrolled Keywords: oceanography,palaeontology ,/dk/atira/pure/subjectarea/asjc/1900/1910
Faculty \ School: Faculty of Science > School of Environmental Sciences
University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups: Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Faculty of Science > Research Groups > Collaborative Centre for Sustainable Use of the Seas
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Depositing User: LivePure Connector
Date Deposited: 06 May 2021 23:59
Last Modified: 20 Mar 2023 10:49
DOI: 10.5194/os-17-593-2021

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