Artificial Upwelling—A Refined Narrative
ayesha iqbal
Abstract
The current narrative of artificial upwelling (AU) is to translocate nutrient rich deep water to the ocean surface, thereby stimulating the biological carbon pump (BCP). Our refined narrative takes the response of the solubility pump and the CO2 emission scenario into account. Using global ocean-atmosphere model experiments we show that the effectiveness of a hypothetical maximum AU deployment in all ocean areas where AU is predicted to lower surface pCO2, the draw down of CO2 from the atmosphere during years 2020–2100 depends strongly on the CO2 emission scenario and ranges from 1.01 Pg C/year (3.70 Pg CO2/year) under RCP 8.5 to 0.32 Pg C/year (1.17 Pg CO2/year) under RCP 2.6. The solubility pump becomes equally effective compared to the BCP under the highest emission scenario (RCP 8.5), but responds with CO2 outgassing under low CO2 emission scenarios.
Key Points
Artificial upwelling (AU) effectiveness to draw down CO2 from the atmosphere is strongly dependent on the future CO2 emission scenario
The solubility pump becomes as effective as the biological carbon pump under high emission scenarios
Organic matter transfer efficiency decreases under AU, likely due to higher water temperatures below the ocean's surface
Plain Language Summary
Artificial upwelling (AU) is a proposed marine carbon dioxide removal (CDR) method, which suggests deploying pipes in the ocean to pump deep water to the ocean's surface. This process theoretically has several different impacts on the surface layer including an increase in the nutrient concentration, as well as a decrease in surface water temperature. Changes in the carbon cycle and associated with biological components are covered by the biological carbon pump (BCP), while changes via physical-chemical processes are covered by the solubility pump. Using numerical ocean modeling and simulating almost globally applied AU between the years 2020 and 2100 under several different atmospheric CO2 emission scenarios, we show that AU leads under every simulated emission scenario to an additional CO2-uptake of the ocean, but the potential increases under higher emission scenarios (up to 1.01 Pg C/year (3.70 Pg CO2/year) under the high CO2-emission scenario RCP 8.5). The individual contribution via the BCP is under every emission scenario positive, while the processes associated with the solubility pump can lead to CO2-uptake under higher emission scenarios and CO2 outgassing under lower emission scenarios.
Theoretical concept of the processes stimulated by artificial upwelling (black lines) and their impact on the air-sea CO2 flux and the surface ocean (box below air-sea boundary). Arrows in the atmosphere indicate air-sea CO2 flux direction, arrows in the ocean indicate tracer movement and colors red/blue indicate respective water temperature increase/decrease. (a) Covers the increase in primary production and export production associated with the biological carbon pump (green), (b)–(e) cover the impacts of the individual processes associated with the solubility pump.
Source: AGU