Carbon Sinks Archives | Ocean 14 Capital Limited

Ocean’s carbon storage capacity surpasses IPCC estimates by 20%

niki — Fri, 29 Dec 2023 21:33:19 +0000

Oceans play a pivotal role in the Earth’s climate system, regulating the climate by absorbing and distributing heat globally, elevating atmospheric humidity, and acting as a significant carbon sink.

The ocean’s carbon storage capacity was underestimated by 20% in the latest IPCC report, according to a study published in Nature.

What’s happening? The ocean’s carbon storage capacity was underestimated by 20% in the latest IPCC report, according to a study published in Nature.

Plankton plays a crucial role in transporting carbon from surface waters to the seabed by converting CO₂into organic tissue. As plankton die, they form “marine snow”, sinking to the seabed, storing carbon, and providing nutrients for deep-sea organisms.

Analysing decades of oceanographic data, the study estimates the ocean’s carbon storage at 15 gigatonnes per year, a 20% increase from previous IPCC estimates. While insufficient to offset current CO₂ emissions, this discovery underscores the ocean’s vital role in long-term climate regulation.

Why does this matter? The oceans play a pivotal role in the Earth’s climate system, serving as a primary force in maintaining the planet’s climatic equilibrium for thousands of years. Their regulation involves absorbing and distributing heat globally, elevating atmospheric humidity, and acting as a significant carbon sink.

The ecosystem services provided by the world’s oceans render Earth a habitable planet. For example, oceanic biogeochemical processes contribute to providing at least half of the Earth’s atmospheric oxygen.

The ocean’s role in global temperature control cannot be overstated. Researchers estimate that if the ocean stopped absorbing atmospheric heat, the average global temperature would sit at 50C, up from 15˚C today. In some areas, temperatures would exceed 100˚C.

The ocean is the largest carbon sink on Earth, holding approximately 38,000 billion tonnes of carbon – over 28 times more than land vegetation and the atmosphere combined. The ocean’s ability to absorb, store and release carbon has shaped the Earth for millions of years.

In geological timescales, this mechanism has both caused and ended ice ages. In more recent times, since the onset of the Industrial Revolution in the mid-19th century, the oceans have absorbed almost one-third of human-induced CO₂ emissions.

How does it work? The ocean stores carbon via two pathways, known as the biological carbon pump and the solubility carbon pump.  The biological pump is responsible for the vast majority of the carbon stored within the ocean, with an estimated 15 gigatonnes of carbon sequestered via this mechanism each year, according to the aforementioned study.

In the sunlit layer of the ocean, tiny plants called phytoplankton use sunlight to perform photosynthesis, extracting CO₂ from the atmosphere and converting it into organic matter.

This process, known as primary production, forms the foundation of food chains in the ocean. Despite the small size of these plants, they generate large amounts of dissolved organic carbon (DOC) to sustain marine food chains.

A portion of the produced organic material sinks to the ocean depths before being stored in sediments for millennia. An estimated 0.1%-1% of these sediments go on to become fossil fuels.

The second, less productive carbon pathway is powered by physico-chemical processes, known as the solubility pump. Here, surface waters in cold regions absorb atmospheric CO₂ and become dense, sinking to vast depths and effectively storing carbon.

These processes are crucial for removing CO₂ from the carbon cycle over long periods. However, the rapid release of carbon into the atmosphere by human activities contrasts with the slower rate of CO₂ sequestration by photosynthesis and CO₂ absorption.

Concerningly, a growing body of literature suggests that climate change may impact both the biological and solubility pumps. For example, warmer waters lower the capacity of the solubility pump.

The behaviour of the biological pump is harder to predict, however, as temperature, light, inorganic nutrients, and pH, among a variety of other variables, will have a significant impact on phytoplankton’s productivity.

As the climate crisis worsens, calls to utilise geoengineering solutions in the ocean have intensified. Suggestions in the past have included ocean fertilisation, where iron is used to simulate plankton growth. However, a study conducted by MIT suggested that ocean fertilisation may have no impact on the global scale.

Seaweed farming is a rapidly advancing ocean carbon removal method. Numerous startups and research initiatives are exploring the feasibility of cultivating seaweed, and then submerging it in the deep sea as an efficient means of capturing and storing carbon.

The US start-up Running Tide is initiating field trials near Iceland, deploying thousands of wooden buoys as small floating kelp farms. Once the buoys dissolve, the seaweed they foster sinks into the deep ocean.

UK must devise ‘climate-smart’ fishing strategy

Hannah — Tue, 31 Aug 2021 10:33:00 +0000

Why does this matter? As the report outlines, fisheries are both vulnerable to climate change impacts and also contribute to it, through direct vessel emissions and fishing equipment disrupting the seabed. Protecting the ocean and its marine habitats – which can sequester more carbon per unit area than forests – is critical to mitigating climate change. In the UK, saltmarsh and seagrass meadows store around 220 million tonnes of blue carbon, 93% of which is sequestered in marine sediments.

The report highlights three key areas to be addressed. First, tackling direct emissions from fishing vessels. UK fishing fleets generate an estimated 914.4 kilotons of CO2 annually – the equivalent of the annual energy usage of over 110,000 US households. WWF, the MCS and RSPB highlight that over half of the UK’s fleet still in operation is over 30 years old. Most vessels in this ageing fleet are powered by carbon-intensive heavy fuel oils, while half relies heavily on diesel.

Second, marine biodiversity should be improved by minimising and potentially reversing damage from poor practices and destructive fishing gear. Around 87% of fish caught by UK vessels use a combination of demersal and beam trawl, and seine nets, which damage muddy sediments and seagrass. When disturbed from the seabed carbon re-mineralises into the ocean and can be released back into the atmosphere, increasing greenhouse gas levels.

Third, the UK’s marine habitats require increased protection to improve their ability to act as a carbon sink, the report states, as blue carbon is further extracted when fish stocks are depleted. The first UK fish stock audit post-Brexit, published earlier this year, found only three of the UK’s top ten fish populations are fished at or under their maximum sustainability yield. Alongside fish and shellfish, larger species are also considered carbon stores, with species such as tuna estimated to be 10% to 15% carbon. This leaves the ocean system when they are fished.

Adopting a climate-smart approach would support the UK’s Fisheries Act, passed last year, which recognises climate impacts in fisheries but has yet to take action in addressing the issue.

Companies are developing solutions to decarbonise vessels, with some exploring alternative fuels such as hydrogen and ammonia to cut carbon from larger, long-range maritime transport. On a smaller scale, electrification is being looked at by several figures in the maritime industry, such as Bio Feeder, which announced plans to charter Norway’s first electric fish feed vessel this summer. Others are experimenting with sail-powered cargo fleets, such as Timbercoast, while SailCargo’s Ceiba vessel combines traditional timber sailing masts with solar-powered engines to achieve commercial-scale zero-carbon shipping.

For smaller fishing vessels, returning to traditional methods could be more appropriate. Cornwall-based Fal Oysters fishery is rooted in low-emission fishing practices, using just sail power and a lower impact approach to harvesting seafood.

To better protect the UK’s blue carbon-storing habitats, bottom trawling is set to be banned within Marine Protected Area (MPA) networks and increased limitations are due to be enforced outside of MPAs.

Less-destructive alternatives such as bottom longlines will require incentives to encourage positive action. Certain initiatives are aiming to reinvent less disruptive fishing gear, such as the Cyprus-based project SEALIVE, which is developing bio-based fishing nets made with natural materials including micro-algae. The nets are also compostable on an industrial scale.

Source:

https://media.mcsuk.org/documents/Climate_Smart_Fishing_Report_FINAL.pdf

UNESCO’s marine world heritage sites store five billion tonnes of blue carbon

Hannah — Sun, 21 Mar 2021 11:51:00 +0000

What’s happening? Three world heritage listed marine sites in Australia – the Great Barrier Reef, Shark Bay and the Ningaloo coast – store over two billion tonnes of carbon dioxide (CO2) in their seagrass meadows, coastal mangroves and tidal marshes, according to a report from UNESCO. The agency has calculated the blue carbon stored in its 50 such sites, and estimated they collectively house around five billion tonnes of CO2 and other greenhouse gases. The sites in Australia store almost 40% of this total.

Why does this matter? Alongside forests and other land-based ecosystems, which more commonly come to mind when thinking about carbon sinks, blue carbon ecosystems are increasingly recognised as having a key role to play in tackling climate change.

UNESCO’s report indicates that marine world heritage sites, despite covering less than 1% of the ocean’s area, represent 15% of total blue carbon assets. Such marine habitats store carbon accumulated over thousands of years, which is locked into sediments. They also sequester more carbon per unit area than terrestrial forests – and at a faster rate. Coastal habitats are particularly important, representing less than 2% of ocean area but accounting for around half the carbon sequestered in ocean sediments.

The Great Barrier Reef, which has a conservation outlook status of “critical”, holds more blue carbon than any other of UNESCO’s sites, demonstrating the importance of protecting its seagrass meadows as well as its corals. UNESCO estimates the reef’s seagrass meadows hold one billion megagrams of organic carbon, or 11% of the world’s total. Its tidal marsh area holds a similar amount.

Action is needed to protect the reef and its corals. The Australian government recently ranked the marine environment along the reef’s coastline at a “D” grade, though improvements in water quality were recorded at some Australian land catchment areas with run-off that affects the reef – such as Cape York and Fitzroy – due to improved agricultural practices. Alongside scientific efforts to protect the reef ecosystem, market mechanisms are being employed to improve water run-off, such as the HSBC-backed “Reef Credits” market which works in a similar fashion to carbon credits by assigning a value to improving the quality of water flowing into the reef.

A further recent study looking at blue carbon has quantified that, alongside its negative biodiversity implications, the practice of bottom trawling is responsible for “one billion tonnes of underwater emissions” each year. This is comparable to Germany’s CO2 emissions, and has also been likened to the emissions output of the aviation industry. The study estimates Croatia’s bottom-trawling emissions, for example, at 23 million tonnes a year – an equivalent amount to the country’s recorded greenhouse gas inventory.

Not all the CO2 released from seafloor sediments enters the atmosphere, but that which stays in the ocean causes acidification. The researchers state that increasing the status of Marine Protected Areas (MPAs) and banning industrial fishing in 3.6% of the ocean would cut 90% of the risk of carbon disturbance from bottom trawling. This can be applied to the UK where, according to the Marine Conservation Society, trawlers operate in all but one of the country’s MPAs. Recently, however, the UK government has proposed to outlaw bottom trawling in four MPAs including the Dogger Bank special conservation area – a key breeding ground for cod, whiting and sand eels.

Alongside protecting existing stores of blue carbon, seeding new ones is equally important. Also, in the UK, one million seagrass seeds are to be planted off the Welsh coast to create a 20,000 sq m meadow as part of one of the largest-ever projects to restore seagrass habitats.

Sources: The Guardian, UNESCO: Custodian’s of the Globe’s Blue Carbon Assets