Will the oceans save us? - 317
Science News, published by The Society for Science, has created a series of articles titled “The Climate Fix.” April’s focus was on the role the oceans can play in speeding the sequestration of carbon from the atmosphere.
Drawing carbon out of the atmosphere and sequestering it in the ocean, often called ocean carbon sequestration, is a critical strategy in the global fight against climate change. The oceans play a massive and vital role in the carbon cycle, acting as both a source and a sink for carbon dioxide (CO2). By enhancing the natural processes that absorb CO2, we can significantly reduce the concentration of greenhouse gases in the atmosphere. Here is an introduction to some methods, benefits, and potential challenges of ocean carbon sequestration.
One of the primary methods of ocean carbon sequestration is through biological processes, particularly phytoplankton growth. Phytoplankton are microscopic marine plants that utilize CO2 for photosynthesis, converting it into organic carbon. Do not underestimate the power of these minute creatures. Though tiny, they already do half the natural sequestering of CO2. When these organisms die, they sink to the ocean floor, effectively removing the carbon from the surface waters and sequestering it in the deep ocean. This process, known as the biological pump, can be enhanced through nutrient fertilization. Adding nutrients such as iron, nitrogen, or phosphorus to ocean regions where these are limiting factors can stimulate phytoplankton blooms, thereby increasing CO2 uptake. Iron fertilization has garnered significant attention due to its potential to induce large-scale phytoplankton growth.
Another promising approach is promoting seaweed farming. Seaweed, or macroalgae, proliferates and absorbs CO2 as it photosynthesizes. Large-scale seaweed farms could not only sequester carbon but also provide a sustainable source of biomass for bioenergy or as a raw material for various industries. Additionally, seaweed can be harvested and processed into biochar, a stable form of carbon that can be buried or used to improve soil quality, effectively locking away the carbon for centuries.
Chemical methods of ocean carbon sequestration involve increasing the alkalinity of seawater to enhance its capacity to absorb CO2. One approach is ocean alkalinity enhancement, where alkaline substances such as crushed olivine or limestone are added to seawater. The mineral enhancement increases the water’s capacity to neutralize carbonic acid, allowing it to absorb more CO2 from the atmosphere. Another method is direct CO2 injection, where captured CO2 is compressed and injected into the deep ocean, where it is stored in stable forms either as dissolved CO2 or as solid hydrates on the ocean floor.
The benefit of ocean carbon sequestration cannot be overestimated. First and foremost, by removing CO2 from the atmosphere, we can slow the rate of global warming, reduce the frequency and severity of extreme weather events, and mitigate the impacts on ecosystems and biodiversity. Furthermore, some methods, such as seaweed farming, offer co-benefits, including sustainable food production, biofuel generation, and creating jobs in coastal communities.
Despite its potential, ocean carbon sequestration also faces significant challenges and risks. One primary concern is the ecological impact of altering marine environments. For example, large-scale iron fertilization could lead to harmful algal blooms or disrupt marine food webs. Similarly, adding alkaline substances to seawater could affect local water chemistry and aquatic life. The long-term effectiveness and stability of sequestered carbon, particularly for methods like direct CO2 injection, still need to be determined and require extensive monitoring and research. Furthermore, the technical and logistical challenges of implementing these methods globally are formidable, necessitating significant investment and international collaboration.
Many solutions, such as seaweed farming, ocean fertilization, enhanced rock weathering, increasing alkalinity, and direct ocean capture, have been proposed for decades, but funding and public support have been low.
This is rapidly changing. NASA reported that from the 21st of July through the 24th of July, these days all vied for the hottest average temperature in recorded history. Humankind is waking up to the fact that the scientists have been right all along, and we must act to save the planet. With this newfound awareness, science funding to get the greenhouse gases out has improved, and resistance to solutions has lessened.
While time is running out, adopting a cautious and well-regulated approach to ocean carbon sequestration is crucial. Immediate, well funded, scientific research and pilot projects are necessary to understand the ecological impacts, optimize methods, and develop best practices. Public awareness and engagement may be the key elements to success as societal support is crucial for the success of large-scale environmental initiatives.
In conclusion, humankind now realizes we are racing the carbon clock. To survive, we must cease burning fossil fuels. Simultaneously, we must explore ocean carbon sequestration because it presents a promising strategy to mitigate climate change by drawing down atmospheric CO2 and storing it in the ocean. With continued research, responsible practices, and international cooperation, ocean carbon sequestration will play a vital role in our efforts to create a sustainable and resilient future.
References: “Ocean to the Rescue”, Science News 06APR24 “Strategy for NOAA carbon dioxide removal research” NOAA May23 Jessica N Cross et al “A research strategy for ocean-based carbon dioxide removal and sequestration.” National Academies of Science, 2022.
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