4:15 PM - 4:30 PM
[ACG47-03] Biogeochemical float observation in the Kuroshio recirculation region under the Hotspot 2 project
Keywords:Argo, Biogeochemical observation, Kuroshio recirculation region, Air-sea interaction
The A02-5 group of the MEXT Grant-in-Aid for Scientific Research on Innovative Areas “Mid-latitude ocean-atmosphere interaction hotspots under the changing climate” project (Hotspot 2; JFY2019-2023) deployed 13 profiling floats with biogeochemical (BGC) sensors in the recirculation region south of the Kuroshio and the Kuroshio Extension from February 2021 to September 2023, conducting physical/BGC observations at 5-day interval for 2.5 years with a primary focus on Subtropical Mode Water.
These floats were an APEX type manufactured by Teledyne Webb Research, equipped with an SBE-41 CTD sensor module supplied by Sea-Bird Scientific and a RINKO ARO-FT dissolved oxygen sensor supplied by JFE Advantech (This was a first pilot deployment of floats with RINKO sensor). Four floats out of 13 were also equipped with SeaFET pH sensor supplied by Sea-Bird Scientific. For the RINKO ARO-FT sensors, we performed calibration in the laboratory and aging using a pressure tank before the float deployment. After a one-year delay due to COVID-19 issues, we deployed 12 floats in February-June of 2021 and the remaining one in April 2022. Previous BGC float deployments around Japan under S1-INBOX and ACE-INBOX projects by JAMSTEC and P-MoVE project by Ocean University of China targeted intensive observations in mesoscale eddies. In contrast, we deployed our floats widely over the Kuroshio recirculation region with a density of about one float per 5-degree square. This will constitute part of global BGC float network targeted under the OneArgo mission, realizing buildup of observing network based on the common platform of BGC and Core floats.
Although one float did not operate at all from the beginning, the remaining 12 floats repeated 92-256 (avg. 181) observations at 5-day interval for periods of 1 year 0 months to 2 years 4 months (avg. 2 years 0 months) (Fig. 1). The gain and offset of dissolved oxygen data was corrected based on comparison between the shipboard observation data on the float deployment and the first float observation data. Then the temporal drift of dissolved oxygen data was corrected using the oxygen concentration in the air measured by floats on their each surfacing. As a result, we successfully obtained accuracy close to the nominal accuracy (the larger of 2 umol/kg and 2%). The pH data were corrected through a comparison with the value estimated empirically by temperature, salinity, and dissolved oxygen. The results of preliminary analyses of these data will be also presented.
Fig.1 Trajectory of 13 floats. The deployment and last observation points of floats are shown by squares and stars, respectively. Seven-digit number shows the WMO ID of floats. Red color denotes floats equipped with pH sensor.
These floats were an APEX type manufactured by Teledyne Webb Research, equipped with an SBE-41 CTD sensor module supplied by Sea-Bird Scientific and a RINKO ARO-FT dissolved oxygen sensor supplied by JFE Advantech (This was a first pilot deployment of floats with RINKO sensor). Four floats out of 13 were also equipped with SeaFET pH sensor supplied by Sea-Bird Scientific. For the RINKO ARO-FT sensors, we performed calibration in the laboratory and aging using a pressure tank before the float deployment. After a one-year delay due to COVID-19 issues, we deployed 12 floats in February-June of 2021 and the remaining one in April 2022. Previous BGC float deployments around Japan under S1-INBOX and ACE-INBOX projects by JAMSTEC and P-MoVE project by Ocean University of China targeted intensive observations in mesoscale eddies. In contrast, we deployed our floats widely over the Kuroshio recirculation region with a density of about one float per 5-degree square. This will constitute part of global BGC float network targeted under the OneArgo mission, realizing buildup of observing network based on the common platform of BGC and Core floats.
Although one float did not operate at all from the beginning, the remaining 12 floats repeated 92-256 (avg. 181) observations at 5-day interval for periods of 1 year 0 months to 2 years 4 months (avg. 2 years 0 months) (Fig. 1). The gain and offset of dissolved oxygen data was corrected based on comparison between the shipboard observation data on the float deployment and the first float observation data. Then the temporal drift of dissolved oxygen data was corrected using the oxygen concentration in the air measured by floats on their each surfacing. As a result, we successfully obtained accuracy close to the nominal accuracy (the larger of 2 umol/kg and 2%). The pH data were corrected through a comparison with the value estimated empirically by temperature, salinity, and dissolved oxygen. The results of preliminary analyses of these data will be also presented.
Fig.1 Trajectory of 13 floats. The deployment and last observation points of floats are shown by squares and stars, respectively. Seven-digit number shows the WMO ID of floats. Red color denotes floats equipped with pH sensor.