Oceans have acidified more in the last 200 years ‘than they did in the previous 21,000 years’

Man-made carbon emissions have acidified the world’s oceans far beyond their natural levels, new research suggests.

In some regions, acidity levels rose faster in the last two centuries than it did in the previous 21,000 years, a study from the University of Hawaii has shown.

Ocean acidity makes it harder for organisms such as molluscs and coral to construct the protective layers they need to survive.

Scientists looked at changes in the saturation level of aragonite, a form of calcium carbonate used to measure ocean acidification.

Unprecedented, man-made trends in ocean’s acidity

Nearly one-third of CO₂ emissions due to human activities enters the world’s oceans. By reacting with seawater, CO₂ increases the water’s acidity, which may significantly reduce the calcification rate of such marine organisms as corals and mollusks. The extent to which human activities have raised the surface level of acidity, however, has been difficult to detect on regional scales because it varies naturally from one season and one year to the next, and between regions, and direct observations go back only 30 years.

Combining computer modeling with observations, an international team of scientists concluded that anthropogenic CO₂ emissions over the last 100 to 200 years have already raised ocean acidity far beyond the range of natural variations. The study is published in the January 22 online issue of Nature Climate Change.

The team of climate modelers, marine conservationists, ocean chemists, biologists and ecologists, led by Tobias Friedrich and Axel Timmermann at the International Pacific Research Center, University of Hawaii at Manoa, came to their conclusions by using Earth system models that simulate climate and ocean conditions 21,000 years back in time, to the Last Glacial Maximum, and forward in time to the end of the 21st century. They studied in their models changes in the saturation level of aragonite (a form of calcium carbonate) typically used to measure of ocean acidification. As acidity of seawater rises, the saturation level of aragonite drops. Their models captured well the current observed seasonal and annual variations in this quantity in several key coral reef regions.

Detecting regional anthropogenic trends in ocean acidification against natural variability

Since the beginning of the Industrial Revolution humans have released ~500 billion metric tons of carbon to the atmosphere through fossil-fuel burning, cement production and land-use changes. About 30% has been taken up by the oceans. The oceanic uptake of carbon dioxide leads to changes in marine carbonate chemistry resulting in a decrease of seawater pH and carbonate ion concentration, commonly referred to as ocean acidification. Ocean acidification is considered a major threat to calcifying organisms. Detecting its magnitude and impacts on regional scales requires accurate knowledge of the level of natural variability of surface ocean carbonate ion concentrations on seasonal to annual timescales and beyond. Ocean observations are severely limited with respect to providing reliable estimates of the signal-to-noise ratio of human-induced trends in carbonate chemistry against natural factors. Using three Earth system models we show that the current anthropogenic trend in ocean acidification already exceeds the level of natural variability by up to 30 times on regional scales. Furthermore, it is demonstrated that the current rates of ocean acidification at monitoring sites in the Atlantic and Pacific oceans exceed those experienced during the last glacial termination by two orders of magnitude.

Seminar:”Crossing Borders”: Ocean acidification lessons from Commercial species and Guidelines for the future

14 February

Prof Chris Bridges (from Duesseldorf University, Germany)

“Crossing Borders”: Ocean acidification  lessons from Commercial species and Guidelines for the future

UCT Oceanography Seminar Room at 13h00

Planet Under Pressure 2012: Session on ocean acidification: ecological impacts and societal implications

Monday 26 March 2012 – State of the Planet, 14:00

Room 10

Ocean Acidification: ecological impacts and societal implications. Session 1 – the science

Chaired by Wendy Watson-Wright

Convenors: Phil Williamson, NERC/University of East Anglia; Carol Turley, Plymouth Marine Laboratory; Sarah Cooley, Woods Hole Oceanographic Institution; Richard Feely, NOAA; Nafees Meah, UK Department of Energy & Climate Change

Ocean acidification is a direct, unavoidable and far-reaching consequence of increased carbon dioxide emissions. This session will focus on the impacts and implications of CO2-driven changes in ocean chemistry for organisms, ecosystems, human society and policy. In addition to four expert overview presentations on those topics, the session includes a short film and a panel discussion.

Measuring ocean acidification impacts in the Southern ocean

For the past two months, a research team (B-199-M) led by Environment and Sustainability Program faculty member, Dr. Sean Place, has been deployed to McMurdo Station, Antarctica working to collect data on the physiological response of endemic fish species of the Ross Sea to a high CO2 environment.

They are currently in the first year of a three-year project focused primarily on members of the Nototheniidae family of fishes that possess a suit of unique physiological adaptations that allow them to exist at the edge of the freezing point of seawater (~ -1.9 C).

A huge experiment

I like how Bill McKibben talks about climate change in his book “Eaarth.” Humans’ impact on the climate is like “a huge experiment,” one that has never been run before. We get to watch it play out before our very eyes, without a control, and without any true sense of the outcome. We are only beginning to understand the scale of this experiment, and the consequences of running it. But it’s clear that there is change happening now. And it’s happening faster than anyone would have dreamed.

Of all the consequences of releasing billions of tons of greenhouse gases into the atmosphere, the most intriguing and unnerving to me is the change it’s causing in the ocean.

“It’s basic science,” said Brian Baird, former Congressman and the last speaker at a town hall meeting I attended in Seattle last month. The presentation, “Dissolving Before Our Eyes: The Acidification of Our Oceans, and Why It Matters to All of Us”. Speakers discussed the science, policy, and social sides of ocean acidification—and why we all need to pay attention.

High CO2 in ocean can cause brain damage in fish (audio)

TONY EASTLEY: An international team of scientists says rising carbon dioxide concentrations in sea water can cause significant damage to the brains of fish.

More than two billion tonnes of carbon dioxide emissions are dissolved into the world’s oceans each year causing changes in the chemical makeup of the water.

Professor Philip Munday told AM’s Bronwyn Herbert that they found marked changes in the behaviour and sensory ability of young coral fish.

UNESCO: Oceans could be 150% more acidic by 2100 (video)

Most of the cliffs that you see bordering the south of England and the Normandy coast were built by deposition of sediments of shellfish that have grown in steady conditions of carbonate and CO2 available in the oceans at geological scale.

It is supposed that this should still continue, as carbon is trapped in the shells of mollusks in a permanent and stable manner, but we suspect that the future will be different.

Rising levels of atmospheric carbon dioxide (CO2) are causing the ocean to acidify at rates not seen for the last 20 million years.

Atmospheric carbon dioxide is absorbed by the ocean (at least half of all emissions pass into the seas) increasing the acidity and resulting in “Ocean Acidification”.