Pollution talks are often about the atmopshere, but we tend to foger that the most part of the pollution goes into the oceans. About a quarter of the carbon dioxide emitted by humans ends up in the seas, which causes them to become more acidic, significantly altering the oceanic environment on which corals, fish, and ultimately, we depend on.

A global look at ocean pH reveals that the water is more alkaline (basic) in the open ocean than in many coastal regions. The more alkaline the water is, the better poised it is to resist ocean acidification.
Credit: Ifremer/ESA/CNES

Ocean acidification is the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere. An estimated 30–40% of the carbon dioxide released by humans into the atmosphere dissolves into oceans, rivers and lakes. Unfortunately, that type of pollution is easier to miss, because we live on land – not in the ocean.

You might tend to think that the CO2 spreads evenly throughout the oceans, but that’s not really true. Ocean acidification is not even, and it can be quite hard to measure and map it. In 2014, Taro Takahashi, a geochemist at Columbia’s Lamont-Doherty Earth Observatory published global acidification maps and showed that we are causing huge damage to the planetary oceans. He also established a standard for future measurements.

“We have established a global standard for future changes to be measured,” said Takahashi, who published the maps with his colleagues in the August issue of the journal Marine Chemistry. The maps provide a monthly look at how ocean acidity rises and falls by season and geographic location, along with saturation levels of calcium carbonate minerals used by shell-building organisms.

Five years of global sea-surface salinity from space. (Image by European Space Agency)

Now, researchers at the University of Exeter in the United Kingdom have tried a different approach – measuring the ocean acidification via satellite measurements. Previous measurements relied mostly on in-situ measurements – taking samples from several areas in the world and interpolating the data. Analyzing the samples and operating the vessels for acquiring the samples is very expensive.

“We are pioneering these techniques so that we can monitor large areas of the Earth’s oceans, allowing us to quickly and easily identify those areas most at risk from the increasing acidification,” study leader Jamie Shutler, a senior lecturer in ocean science at the University of Exeter, said in a statement.

This new approach also allows relatively easy measurements of areas which are hard to access. This technology has the potential to become the easiest and most efficient way of quantifying oceanic acidity – especially as satellite sensors continue to develop. Dr Jamie Shutler from Geography at the University of Exeter’s Penryn Campus in Cornwall who is leading the research said:

“Satellites are likely to become increasingly important for monitoring ocean acidification, especially in remote waters. We are pioneering this data fusion approach so that we can observe large areas of Earth’s oceans, allowing us to quickly and easily identify those areas most at risk from increasing acidification.”

The results of the study are pretty dire: the pH at the ocean’s surface become 30 percent more acidic since the start of the Industrial Revolution. Open regions of the ocean show this resilience, while many coastal regions appear less alkaline. The northeastern United States looks particularly vulnerable – a finding which confirms previous studies.