SCALING OCEAN CARBON SEQUESTRATION & VERIFICATION

The following is by Ian D. Walsh; ianwalsh@comcast.net; @iandavidwalsh; adapted from Ian’s WHOI OCB Summer Workshop Presentation at Woods Hole, MA, 20-23 June 2022 for website form by Salvador Garcia. Acknowledgments: IDW consults for Ocean-Based Climate Solutions Inc. (Ocean-Based) which has developed and built artificial upwelling pumps and is testing the systems. Ocean-Based did not directly pay for or have editorial control of the research presented here.

INTRODUCTION

The idea of artificial upwelling using vertical tubes in the ocean open has been around for a long time (Stommel et al., 1956). Similarly, the linkage of atmoCO2 to ocean upwelling on a global scale through recent geological time has been long established (Dymond and Lyle, 1985). Current considerations of the potential impact of artificial upwelling have outlined an uncertainty matrix and a research strategy for artificial upwelling within a broader review of ocean-based carbon dioxide removal (CDR) (NASEM, 2021). Meanwhile, the carbon offset ‘market’ is booming (your favorite news source), including ocean CDR.

Here I present some considerations and calculations on the scalability of artificial upwelling and verification pathways to hopefully advance the discussion and spark interest in the OCB community.

OLIGOTROPHIC OCEAN: HAWAII OCEAN TIME SERIES NUTRIENT DATA

The oligotrophic ocean is an attractive deployment location or artificial upwelling at least through the testing phase because the generally low abundance of nutrients in the absence of upwelling provides an excellent background to track the impact of artificial upwelling and a source of excess phosphate at depth to test Karl and Letelier’s hypothesis that net sequestration CO2 is driven by excess phosphate.

Redfield ratio plot of the concentration of phosphate and nitrate at HOT in 2018 from bottle data taken between 480 and 520 meters depth. There is a consistent 0.3 uM/kg ‘excess’ phosphate concentration through the year except for the May 2018 data set.

Data obtained via the Hawaii Ocean Time-series HOT-DOGS application; University of Hawai’i at Mānoa. National Science Foundation Award # 1756517

PARTNERSHIPS TO DRIVE VERIFICATION

Verification of sequestration should be independent from the deployment and operation of sequestration technologies, though these should be tightly linked to drive the system towards increase effectiveness.

Continuation of public strategies to measure and model ocean carbon dynamics will contribute to ocean CDR measurements and verification.

Local modeling for additionally and effectiveness of ocean CDR technologies should couple with wider scale public modeling efforts.

Costs for verification relative to ocean CDR will then be spread between the operators of ocean CDR and the wider public and reduce conflict of interest uncertainties.

Autnomous vehicles with physical and biogeochemical sensors such as the Bio-Argo float should be deployed in the vicinity of artificial upwelling to provide near-field data to verify additionality.
ARTIFICIAL UPWELLING – WAVE ENERGY DRIVES THE SYSTEM
Schematic of the Ocean-based wave-powered Ocean Upwelling Pump technology, which uses flapper valves on the intake to drive deep water to the surface.
Deployment of an Ocean Upwelling Pump system surface package with the fabric tube spooled up on the bottom-weight one-way valve on deck.
SENSITIVITY AND DETECTION
A simple volumetric dispersion model suggests that a 5000 m3 hr1 pump rate would be detected by a backscattering sensor after seven days with a front width of about 60 meters, sixty kilometers ‘downstream’ of the pump.
SCALING: IS ONE GIGATON CO2 PER YEAR POSSIBLE?
Conservative potential sequestered carbon fixed per pump based on HOT nutrient data set. Karl and Letelier’s 2008 estimates are about a factor of 4 higher.
REFERENCES

Stommel, H., Arons. A.B., and Blanchard, D., 1956: An oceanographical curiosity: the perpetual salt fountain. Deep Sea Research, Vol. 3, pp. 152-153. https://www.sciencedirect.com/science/article/abs/pii/0146631356900958?via%3Dihub

Dymond, J. and Lyle, M. 1985. Flux comparisons between sediments and sediment traps in the Eastern Tropical Pacific: Implications for atmospheric CO2 variations during the Pleistocene. Limnology and Oceanography, 30(4), pp. 699-712. https://www.researchgate.net/publication/237388050_Flux_comparisons_between_sediments_and_sediment_traps_in_the_Eastern_Tropical_Pacific_Implications_for_atmospheric_CO2_variations_during_the_pleistocene

Karl, David & Letelier, Ricardo. 2008. Nitrogen fixation-enhanced carbon sequestration in low nitrate, low chlorophyll seascapes. Mar. Ecol. Prog. Ser. 364, 257-268. https://www.researchgate.net/publication/238005444_Karl_D_M_Letelier_R_M_Nitrogen_fixation-enhanced_carbon_sequestration_in_low_nitrate_low_chlorophyll_seascapes_Mar_Ecol_Prog_Ser_364_257-268

National Academies of Sciences, Engineering, and Medicine. 2021. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington, DC: The National Academies Press. https://doi.org/10.17226/26278

Kithil, P., Garcia, S., and Walsh, I., 2022. Ocean Carbon Dioxide Removal using Wave-powered Artificial Upwelling Pumps. The Journal of Ocean Technology, Vol. 17, No. 1, 2022. https://issuu.com/journaloceantechnology/docs/e-jot_vol17n1_interactive_book_lr_flipbook