Science

How we discovered that the ocean surface absorbs far more carbon dioxide than previously thought

Credit: Pixabay/CC0 Public Domain

The ocean plays a vital role in capturing carbon dioxide (CO₂) from the atmosphere and has so far acted as a brake on the full effects of climate change. Current estimates of CO₂ from the atmosphere lost to the ocean, commonly referred to as ocean CO₂ sinks, suggest that approximately 25% of all human CO₂ emissions are absorbed by the ocean.

A recent paper published in Nature Geoscience showed that a thin layer on the ocean’s surface called ‘marine skin’, which is thinner than a human hair, increases this ocean CO₂ uptake by about 7%. Although it sounds like a small difference, this additional absorption is equivalent to the CO₂ absorbed by the entire Amazon rainforest each year.

This long-term uptake of carbon into the ocean has negative effects on ocean health. It is slowly causing ocean acidification, and as seawater absorbs more carbon dioxide, ocean chemistry is changing and pH is dropping, which cannot be easily reversed.

Since the 1990s, scientists have suggested that cooler skin temperatures enhance the uptake of CO₂ by the ocean. Therefore, estimates of CO2 uptake that ignore this effect will be inaccurate.

Since then, sea surface temperature researchers have shown that the ocean’s surface layer is slightly cooler than the ocean water directly below. This surface skin is about 0.17°C cooler on average. These temperature changes increase the concentration of CO₂ in this tiny piece of water. This is important because this water is in direct contact with the atmosphere.

Because the exchange of CO₂ between the ocean and the atmosphere is controlled by the concentration difference between the surface and the underlying water layer, this cooler skin increases the uptake of CO₂ into the ocean.

European researchers confirmed these concentration-driven processes in 2007. They visualized the oxygen gas concentration within these tiny layers in the laboratory using a powerful microscope-like device equipped with a camera. In recent years, the influence of the surface layer on global ocean carbon has been assessed using theory, modeling, and satellite observations, but until now no one had actually measured this influence underwater.

To carry out our research, the European Space Agency helped put expert measurements on board two research vessels taking part in the Transatlantic Meridian Science Cruise, which hosts UK and international scientists each year. He gave it to me.

In 2018, we collected data from a kit aboard the Royal Research Vessel James Clark Ross, which sailed approximately 9,000 miles (14,500 km) from Harwich in southeast England to Port Stanley in the Falkland Islands.

In 2019, the device was installed on the Royal Research Vessel Discovery, which was en route from Southampton, UK, to Puntas Arenas, Chile. The ship sailed in very rough seas in the North Atlantic and near the Falkland Islands, but near the equator it experienced mirror seas with no real waves, so our measurements cover a wide range of different sea conditions. It was reflected in

Up, up, and away?

On each voyage, two sets of measurements were taken. One set of measurements used a micro-weather system to measure wind speed and temperature in conjunction with atmospheric gas measurements. Collectively, this is known as an “eddy covariance system” and tracks the amount of CO₂ gas in the air rising (away from the Earth’s surface) rather than falling. This tells you how much CO₂ the ocean is absorbing or emitting.

The second set of measurements sampled water collected from the ship’s inlet pipe. From this we measured the gas in the water and its temperature. This was then combined with a high-performance thermal camera that measures the temperature of the ocean’s surface layer.

Without the influence of the marine skin, both sets of measurements together should give the same results. These differences have revealed how the marine epidermis affects ocean CO₂ absorption.

Accurately estimating the CO₂ absorbed by the ocean is important for calculating the global carbon budget. These budgets quantify how carbon moves through the Earth system and are used to guide international policy on reducing emissions.

The ocean and atmosphere are two major carbon storage sites that can be accurately observed. Accurately estimating these constrains all other parts of the global carbon budget and allows us to assess what is called the ‘remaining budget’. This identifies how much more carbon can be emitted before a particular climate goal is met. Importantly, it is not possible to estimate the carbon absorbed by all of Earth’s land without first estimating the carbon absorbed by the oceans. An approximately 7% increase in ocean CO₂ uptake would therefore impact the global carbon budget and the Earth’s capacity for further emissions.

As the United Nations climate summit, Cop29, approaches in Azerbaijan, this study will help define the issue of CO₂ emissions more precisely. Climate experts will need to re-evaluate the global carbon budget to reflect our new findings, but this additional ocean absorption will create a budget imbalance and preclude land-based carbon sinks from currently being considered. is potentially less effective at removing carbon from the atmosphere. emissions.

It sounds positive that the ocean is absorbing more carbon dioxide emissions than previously thought. But this news means climate change and other human activities, such as overfishing and pollution, are putting increasing pressure on ocean health. It may also imply that the land’s ability to absorb CO₂ is overestimated and that more attention needs to be paid to the conservation of marine ecosystems.

As the need to reduce emissions and meet reduction targets grows, insights into how the ocean’s skin works will help scientists understand how the ocean responds to emissions. Helpful. But unfortunately, that doesn’t put everyone out of danger.

Provided by The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.conversation

Citation: How we discovered the ocean’s surface absorbs far more carbon dioxide than previously thought (November 9, 2024) https://phys.org/news/2024 Retrieved November 9, 2024 from -11-ocean-surface-absorbs-carbon- dioxide.html

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