Artificial upwelling – the idea of greening the ocean
WOR 8 The Ocean – A Climate Champion? How to Boost Marine Carbon Dioxide Uptake | 2024

Artificial upwelling – the idea of greening the ocean

Artificial upwelling – the idea of greening the ocean
> Algae, zooplankton and fish are prime drivers of what is termed the biological carbon pump. This natural process needs nutrients to function properly. Such nutrients, however, are lacking in many places, notably in sunlit surface waters. Pumping up nutrient-rich deep ocean water could remedy this nutrient deficiency. Whether such a step would actually increase the ocean’s natural uptake of carbon is uncertain.
Kick-starting the biological carbon pump fig. 6.7: mauritius images/Andrey Armyagov/Alamy Stock Photos

Kick-starting the biological carbon pump

> Phytoplankton growth is limited on about 75 per cent of the ocean surface, because in those regions the light-filled surface waters do not contain enough nutrients. Deep ocean water, in contrast, tends to be rich in nutrients. This knowledge gave rise to the idea to pump up (“upwell”) nutrient-rich water from several hundred metres below the ocean surface in order to increase algal growth in the sunlit upper layers and thus boost the performance of the biological carbon pump. Whether artificial upwelling will prove useful is uncertain. Research investigating the concept has been presenting scientists with extraordinary technical challenges.

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Artificial upwelling − the verdict: “of limited utility”

“Artificial upwelling” is the term used to describe processes that aim to transport nutrient-rich deep ocean water to the sea surface in order to boost the growth of microscopic algae and thus the ocean’s biological carbon pump.
This would store a certain proportion of the now newly formed biomass in the depths of the ocean and lock away the carbon it contains for several decades to centuries.
However, to function as a negative emission technology the boosted food web must bind and sequester more carbon in the depths of the ocean than outgasses at the surface from the mostly carbon dioxide-rich deep ocean water upwelled to the surface – a requirement that can presumably only be met under very specific conditions, which is why the potential for additional carbon dioxide removal is rather low.
There is also a high degree of uncertainty as to the technical means by which artificial upwelling can be generated on a climate-relevant scale and what risks the processes entail for the marine environment – especially for the numerous biotic communities at mid-depths and in the deep ocean. Uncertainties also surround the regulatory framework that would be required for large-scale deployment, precisely because the use of many pumps would presumably severely restrict other forms of marine use. So far, the use of artificial upwelling would appear to only make sense and be economically worthwhile as an aid in kelp farming. The artificially generated nutrient input from the depths increases the growth of the macroalgae and helps them to absorb more carbon dioxide and bind more carbon in their biomass.