Ocean's Role in Climate Moderation
Oceans absorb 25% of anthropogenic CO2 emissions and more than 90% of excess heat, helping to mitigate climate change.
This process, though vital, causes problems like ocean acidification, disrupted ecosystems, and warming, which harm marine life and the ocean's natural carbon storage capacity.
These ecological impacts undermine the ocean's ability to provide essential services like fisheries and carbon sequestration.
Marine Carbon Dioxide Removal (mCDR)
mCDR are emerging as a way to complement emissions reductions and handle the lingering CO2 in the atmosphere.
Efforts to fight climate change so far have been land-focused, but oceans, seas, lakes, and rivers offer new possibilities for efficient carbon capture.
Deep-water bodies can rapidly remove carbon and transport it to the ocean’s depths, where it binds with minerals and remains stored.
Biotic vs. Abiotic Methods
Biotic approaches (e.g., mangroves, macroalgae) are nature-based solutions that not only sequester carbon but also protect biodiversity and coastal areas.
These biotic solutions are integrated into national climate plans, but their sequestration potential is limited to less than 1 billion tonnes of CO2 annually.
Abiotic techniques, like ocean alkalinity enhancement (OAE) and biomass burial at sea, have a much higher potential to sequester carbon—up to 22 billion tonnes/year.
OAE involves adding alkaline materials to seawater to neutralize CO2, trapping it in the ocean for tens of thousands of years.
Challenges and Potential Risks
Abiotic methods, although promising, face several challenges, including public skepticism, regulatory hurdles, and high energy requirements, especially in processes like mineral mining.
Methods such as ocean iron fertilization and macroalgae cultivation have been criticized for their potential to disrupt marine ecosystems and lower oxygen levels in deeper waters.
Measuring the actual carbon capture and storage effectiveness of mCDR methods remains difficult, and the oceans are expensive and hard to monitor accurately.
While mCDR offers a potential solution, it cannot replace the urgent need for emissions reduction and should be used as a complementary strategy in the transition to net-zero emissions.
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