Biogeochemical Argo Profiling Floats

Measurement of the carbon from below the pump to the surface is provided by biogeochemical ARGO robotic floats. The sensors incorporated on each BGC ARGO are found at https://www.seabird.com/biogeochemical-floats.

Our patent-pending methodology for determining net carbon sequestration is as follows:

“The BGC floats include a sensor package that measures the bulk properties of the most significant oceanic carbon pools that will be affected by the enhanced vertical exchange of water across the thermocline from the pumping technology.

Temperature, salinity and pressure yield the density field and will be used to generate a mixing model of the pumping effect on the vertical transport of the quasi-conservative heat and salt budgets. This constrains the entire system.

The carbon dynamic response to the vertical exchange is measured by the rest of the sensors. The chlorophyll fluorescence and backscattering sensors measure the particle load of particulate organic carbon (backscattering) and the viable phytoplankton (chlorophyll). The FDOM fluorometer measures the concentration of the fluorescent fraction of the dissolved organic matter pool. The pH sensor measures one component of the pCO2 equilibrium and with the backscattering and FDOM sensors monitors net transfers of carbon between the dissolved and particulate pools through autotrophic and heterotrophic activity. The dissolved oxygen sensor constrains net community production of fixed carbon and the impact of gas exchange kinetics on pCO2, Finally, the nitrate concentration measurement monitors the effectiveness of the exchange of nutrient-rich deep water with nutrient-depleted surface water through the pumping process and therefore the net increase in autotrophic carbon production potential achieved by the pumps.

The floats will be deployed in a near field/far field manner with one float within the pumping volume and the other deployed outside the pumping volume. The float mission profiles (park depth, profile interval, the rate and ratio between deep and shallow profiles) will be adjusted during the initial trial period and subsequently during roll out to optimize modeling of the effect of the pumps.

As the system scales, a network effect of increasing data from the floats relative to the governing scales across time and space will decrease the carbon flux measurement uncertainty between any pair of near and far-field floats, resulting in a measurement system that asymptotically approaches a fixed structural relationship between the pumping and the net sequestration of carbon.”

BGC ARGO data is uplinked near real-time to the ARGO data center in France or the USA where it is quality-controlled, then becomes public according to ARGO procedures.

The pathway of the BGC ARGO can be finetuned by modifying the length of the tether rope extending from the valve/bottom-weight, as seen below (patent pending).

Sketch of BGC ARGO tethering.

A sample of possible pathways assuming pump depth 500m and total tether line 2,000m follows:

Table 6. Geometry of BGC ARGO tethering.

The reference BGC ARGO may be a null pump (complete except no valve thus no upwelling); a free-drifting BGC ARGO we deploy outside the pumping region; or may utilize data from 3rd party BGC ARGO’s in the vicinity (if temporal and spatial variability of the reference data is acceptable and representative of the AUP operating region).