TY - JOUR
T1 - Surface ocean carbon budget in the 2017 south Georgia diatom bloom: Observations and validation of profiling biogeochemical argo floats
AU - Coggins, Aimee
AU - Watson, Andrew J.
AU - Schuster, Ute
AU - Mackay, Neill
AU - King, Brian
AU - McDonagh, Elaine
AU - Poulton, Alex J.
N1 - Funding Information:
Special thanks are extended to those involved in the DY086 cruise, including the PSO Richard Sanders, and those who helped in the deployment of the BGC-floats and collection of water samples used for their validation. Cruise DY086 was part of the COMICS project (Controls over Ocean Mesopelagic Interior Carbon Storage; NE/M020835/1). A special thank you is also extended to those who collected and calibrated the glider data. Glider surface chlorophyll timeseries was collected under European Research Council Consolidator grant (GOCART, agreement number 724416). We are also grateful to Robert Drucker who kindly checked the oxygen calibrations that we applied to the float sensors, and to Kenneth Johnson with whom we discussed the pH senor calibrations. Special thanks are also extended to Matthew Humphrey for his advice with regards to the VINTDA equipment and processing and his guidance in the use of the Calkulate software. We would also like to thank EUMETSAT for the accessibility of the Chlorophyll data used in Fig. 1 (Sentinel 3 OLCI instrument: https://www.eumetsat.int/ocean-colour-services ). This research was conducted under the SONATA project and in association with the ORCHESTRA (NE/N018095/1) project. This research was supported by funds (NE/M020835/1, NE/M020835/2) from the UKs Natural Environment Research Council ( NERC ). Aimee Coggins was supported by Royal Society grant RP\EA\180008 and Andrew Watson by Royal Society grant RP140106.
PY - 2023/6
Y1 - 2023/6
N2 - Estimates of the partial pressure of CO2 (pCO2)
derived from biogeochemical Argo floats have the potential to improve our
knowledge of the highly variable and partially observed Southern Ocean carbon
sink through sampling at improved temporal and spatial resolution. Here we use
the data from six biogeochemical Argo floats to characterise near-surface
dissolved inorganic carbon (DIC) concentrations and fluxes at the site of an
intense (Chl-a >3 mg m−3) mesoscale diatom bloom situated northwest
of South Georgia. Concurrently, we provide independent analysis and validation
of the methodology used by the Southern Ocean Carbon and Climate Observational
and Modelling (SOCCOM) project for deriving surface pCO2 from
float-based pH and oxygen measurements. We compare the float observations with
co-located ship data from bottle samples over a month-long period. When
compared to data sampled within 24 hours and 25 km of each float profile, we
find good agreement with a mean offset of −0.005 ± 0.018 (1σ) between float pH
and bottle-derived pH. This translates to comparable pCO2 estimates
between ship measurements and floats with a mean difference of 2.6 ± 12.8 (1σ)
μatm, providing support for the use of biogeochemical Argo float data to
supplement shipboard pCO2 measurements in the
Southern Ocean. Based on float-derived pCO2 we
calculate a sizeable local flux of CO2 of 24 ± 7 mmol C m−2 d−1 (over
a 27-day period) from the atmosphere into the surface mixed layer, driven by a
large air-sea pCO2 gradient and strong but variable
winds. Despite the considerable air-sea flux, the local mixed layer carbon
budget appears to be dominated by entrainment and detrainment of carbon-rich
waters into and out of the mixed layer. However, given the large uncertainties
associated with these fluxes and the significant challenges associated with
closing the mixed layer budget, further research is required to refine
float-based mixed layer DIC fluxes.
AB - Estimates of the partial pressure of CO2 (pCO2)
derived from biogeochemical Argo floats have the potential to improve our
knowledge of the highly variable and partially observed Southern Ocean carbon
sink through sampling at improved temporal and spatial resolution. Here we use
the data from six biogeochemical Argo floats to characterise near-surface
dissolved inorganic carbon (DIC) concentrations and fluxes at the site of an
intense (Chl-a >3 mg m−3) mesoscale diatom bloom situated northwest
of South Georgia. Concurrently, we provide independent analysis and validation
of the methodology used by the Southern Ocean Carbon and Climate Observational
and Modelling (SOCCOM) project for deriving surface pCO2 from
float-based pH and oxygen measurements. We compare the float observations with
co-located ship data from bottle samples over a month-long period. When
compared to data sampled within 24 hours and 25 km of each float profile, we
find good agreement with a mean offset of −0.005 ± 0.018 (1σ) between float pH
and bottle-derived pH. This translates to comparable pCO2 estimates
between ship measurements and floats with a mean difference of 2.6 ± 12.8 (1σ)
μatm, providing support for the use of biogeochemical Argo float data to
supplement shipboard pCO2 measurements in the
Southern Ocean. Based on float-derived pCO2 we
calculate a sizeable local flux of CO2 of 24 ± 7 mmol C m−2 d−1 (over
a 27-day period) from the atmosphere into the surface mixed layer, driven by a
large air-sea pCO2 gradient and strong but variable
winds. Despite the considerable air-sea flux, the local mixed layer carbon
budget appears to be dominated by entrainment and detrainment of carbon-rich
waters into and out of the mixed layer. However, given the large uncertainties
associated with these fluxes and the significant challenges associated with
closing the mixed layer budget, further research is required to refine
float-based mixed layer DIC fluxes.
UR - http://www.scopus.com/inward/record.url?scp=85149673190&partnerID=8YFLogxK
U2 - 10.1016/j.dsr2.2023.105275
DO - 10.1016/j.dsr2.2023.105275
M3 - Article
SN - 0967-0645
VL - 209
JO - Deep-Sea Research Part II: Topical Studies in Oceanography
JF - Deep-Sea Research Part II: Topical Studies in Oceanography
M1 - 105275
ER -
