Based on OSSEs and analyses of global ocean data sets, an array of about 1000 BGC profiling floats would provide the needed resolution to
greatly improve our understanding of biogeochemical processes on a global scale, to reduce the uncertainties of major ocean carbon fluxes,
and to enable the significant improvement of marine resource models. With an endurance near four years for a Biogeochemical-Argo float,
this system would require the procurement and deployment of 250 new floats per year to sustain it.
The lifetime cost for a Biogeochemical-Argo
float, including capital expense, calibration, data management, and data transmission, is about $100,000. A global Biogeochemical-Argo
system would thus cost near $25,000,000 annually. In the present Argo paradigm, the US provides half of the profiling floats in the array,
while EU and Asia share the remaining half. If this continued, the US cost for the Biogeochemical-Argo system would be ~$12,500,000 annually
and ~$6,500,000 for EU and Asia. This presumes that float deployments can be carried on future research cruises of opportunity, particularly
the international GO-SHIP program, which provides essential validation data that is equivalent to the Argo
Developing BGC sensors accurate and stable enough to be deployed on Argo floats is a challenge and different sensors are at different
levels of readiness for inclusion on an operational BGC-Argo float. Currently, regional programs are validating sensor
operation, improving sensor performance, and developing the software tools and expertise
needed to operate a global network that interacts with other components of the global ocean observing system, including satellites
and shipboard programs such as GO-SHIP and various time-series.
For example, analysis of the oxygen data collected by 47 US and
Canadian floats that made air oxygen measurements on each surfacing demonstrates that air calibration significantly improves sensor
performance. It enables oxygen measurements with accuracy comparable to that obtained in the GO-SHIP program (Johnson et al., 2015).
Multiyear records of pH made on profiling floats deployed at the Hawaii Ocean Time-series station (HOT) agree with the shipboard
observations to 0.004±0.007 at the sea surface (Johnson et al., 2016). This exceeds requirements for climate quality pH measurements
specified by the Global Ocean Acidification Observing Network (http://www.goa-on.org/docs/GOAON_plan_print.pdf). Bio-optical
measurements of chlorophyll show no significant bias with satellite remote sensing products (Xing et al., 2011).
The fraction of the Argo array that is equipped with BGC sensors is now approaching 10% (~280 oxygen, 120 bio-optical, 70 nitrate, and 40
pH sensors now operating). Many of these instruments have been deployed in regional programs with dozens of floats that are designed to
produce an integrated data set that can be used to address questions related to physical-biogeochemical coupling in eddies, phytoplankton
phenology, nutrient supply, and climate impacts on ocean carbon cycling.
Examples include regional arrays in
- the Southern Ocean: SOCCOM
- the North Atlantic Sub-polar Gyre: remOcean
- the Mediterranean Sea: NAOS
- the Kuroshio region of the North Pacific: INBOX
The figure above shows a record over 13 years of temperature, oxygen and nitrate data collected from profiling floats deployed near Hawaii that
illustrates mesoscale to interannual variability not seen in conventional sampling.
Links to related pages
Biogeochemical Argo - an extension of the Argo program to include biogeochemical observations: http://biogeochemical-argo.org
SOCCOM - Southern Ocean Carbon and Climate Observations and Modeling: http://soccom.princeton.edu
remOcean -Remotely Sensed Biogeochemical Cycles in the Ocean: http://remocean.eu
NAOS - Novel Argo Ocean observing System: http://en.naos-equipex.fr/
INBOX - Western North Pacific Integrated Physical-Biogeochemical Ocean Observation Experiment: http://www.jamstec.go.jp/ARGO/inbox/index.html
Task team leads
The BGC Argo Task Team is comprised of: