Koweek, David A. “Expected Limits on the Potential for Carbon Dioxide Removal From Artificial Upwelling (June 29, 2022). https://www.frontiersin.org/articles/10.3389/fmars.2022.841894/full

The Koweek study argues that field trials for ocean artificial upwelling are justified, pulling from a plethora of studies that have analyzed a variety of flow rates – which Ocean-based Climate Solutions’ ocean upwelling pump exceeds. Read Dr. Ian Walsh’s comments next regarding the Koweek study and its endorsement for further research.

Dr. Ian Walsh’s comments on David Koweek’s study on Expected Limits on the Potential for Carbon Dioxide Removal From Artificial Upwelling.

  1. The paper demonstrates that a flow rate approximately equal to that observed with published AU flow rates is unlikely to support a production and export response sufficient to reach an mCDR removal rate of 1 gigatonne of CO2atmo/year with pumps deployed uniformly over the world ocean. [N.B. I use tonne to refer to the SI measurement while the paper refers to the imperial ton at least in the text. The difference is immaterial to this review, but I’m presuming the text should use the SI unit spelling as SI units are used in the rest of the text.]
  2.  The model takes into account DIC and TA upwelling and potential outgassing
  3. The model uses a single flow rate (0.05 m3 s-1)
  4. The model uses a variety of C:N:P stoichiometries
    1. C:N:P fixed through primary productivity
    2. Micro and macro algae cases
  5. No explicit export function
    1. No regeneration scaling
      1. Time
      2. Depth
  6. Photoperiod modulation is included in the model
  7. The model uses a 1 AUP km-2 density over most of the world ocean

The nice thing about David Koweek’s study is that it couples gas exchange and DIC and TA upwelling kinetics with a reasonable range of nutrient stoichiometry and results in a positive net carbon sequestration potential. Along with Wu et al., 2022 currently under review (https://doi.org/10.5194/esd-2021-104), the Koweek model demonstrates that artificial upwelling has the potential to impact CO2atmo.

This is important as I consider the primary unknown in terms of impact on AU sequestration potential is the scaling of nutrient stimulated production uptake of pCO2 relative to the carbonate system kinetics. There is still much to learn about this interaction, but at the least, we see that models that include carbonate system dynamics show positive sequestration potential.

Relevant to Ocean-Based:

  1. The flow rate for Ocean-Based’s AUP is estimated to be 5000 m3/hour
  2. This is 27.8 times the Koweek model flow rate
  3. Using the Ocean-Based flow rate to scale the Koweek model results generates a rate of mCDR of 1.39 gigatonnes/year
    1. This is above the 1 gigatonne/year
  4. From an enterprise perspective, the mCDR potential is not based on a basin or ocean scale uniform deployment but on maximizing mCDR income relative to enterprise costs.
    1. AU pump (AUP) density will be a function of maximizing pump efficiency on an mCDR basis per pump per expected pump lifetime. A uniform deployment scenario, while attractive to modeling, is not likely to be efficient from the standpoint of resource allocation or cash flow relative to enterprise costs (capital, operations, maintenance, and MRV costs) and income.
    2. The operative scaling for an enterprise is mCDR/AUP/ocean area/time: moles CO2atmo AUP-1 km-2 time-1
      1. Time: day (diel cycle), monthly (seasonal), annual (seasonal), decadal (life of the pump, ENSO)
    3. The operative scaling for the economic potential includes the cost of mCDR production (pump capital + operations + maintenance + MRV) over the time scale relative to mCDR payments.
  5. The upshot of taking the perspective of the enterprise is that the scaling of the enterprise will result in the selection of the most advantageous milieus for the placement of the marginal (next) pump. ASIDE: This is entirely different from the testing phase, in which experiential concerns and data gathering are the most important considerations. [running a Test, Fail, Advance loop]
  6. If we run the Koweek model as an optimization tool:
    1. What conditions need to be met to generate a global integrated value that is significant?
      1. Sensitivity analysis concerning volume transport
      2. Force depths with optimal PO4ex input values
      3. K&L 2008 & White et al. 2007 papers
    2. Use the HOT data set as input?
    3. Include the annual cycle relative to the wave energy and upwelling volume relative to the dispersion ratio
      1. There is probably an annual cycle in wave energy that begets a dispersion ratio that goes above and below the diatom bloom point (Ulf et al., mesocosm results)
      2. What does that look like on an annual basis?
      3. Determine the seasonal and annual export cycle using multiple modes based on dispersion ratio and volume pumped:
        1. If we look at three modes:
          1. Diatom bloom
          2. Top-down (1% export of primary productivity)
          3. K&L/White et al., diazotroph bloom
        2. Derive the modal export function
          1. Sum over the annual cycle
    4. Derive the future productivity decrease in the central gyres due to increased SST for future additionality
      1. Do a basin match up, e.g., find the warmer temperature data from BGC Argo and calculate areal differences based on projected future temperatures
      2. Look at Behrenfeld et al., 2006 and subsequent papers (where referenced) for a general relationship
  7. The model does not consider export and fractionation
    1. This is an upper limit model
    2. Use the tri-modal export model to refine export and sequestration
    3. Define other benefits from AU
      1. Temperature/stratification feedback
        1. Especially relative to marine heat waves
        2. Especially relative to trophic level restoration and or impact minimization
          1. Highest value might be as a way of creating pockets of ecological stabilization to retain significant populations through the warmer ocean

Striking coherence between maximum chlorophyll maps (e.g. Feldman maps) and the microalgae potential, with perhaps the exceptions of the eastern edges of the South Pacific and South Atlantic which look offset higher in the upwelling potential.

A more recent paper with similar mapping:

Behrenfeld., M., O’Malley, R., Siegel, D., McClain, C., Sarmiento, J., Feldman, G., Milligan, A., Falkowski, P., Letelier, R., and Boss, E. (2006). Climate-driven trends in contemporary ocean productivity. Nature, 444, 752-755.

Philip Kithil’s graph of pumping rate, and pump diameter (as a valid product) whereas Koweek uses pumping rate and depth)

As stated above, Ocean-based Climate Solutions, Inc’s ocean upwelling pump flow rate is significantly higher than the models analyzed in the Koweek paper. This is because flow rate is directly correlated to pipe diameter and less to pipe length (depth of the inlet) as shown in Koweeks’ Figure 1.

A critical consideration found in the Liu and Jin reference cited by Koweek in this Figure 1, and confirmed by us, is that the water column inside the pipe gains momentum, delivering far more volume than a simple wave height x period calculation.  Liu and Jin determined the simple calculated flow rate was 0.45 m/s, whereas the measured flow rate was 0.95 m/s – greater by a factor of 111%! Our own data found a 60% greater measured vs. calculated flow rate.