Ocean Acidification Levels Seen From Space
Ocean acidification has been mapped from space, in a new map that could help chart damage in water around the world.
Around one-quarter of the carbon dioxide released through human activities is absorbed by oceans, where water can transform the gas into carbonic acid. Although this process has temporarily slowed the amount of carbon being released into the atmosphere, it has also raised acidity in oceans, potentially harming marine wildlife. Oceans around the globe have become 30 percent more acidic since the start of the Industrial Revolution, according to the National Oceanic and Atmospheric Administration (NOAA).
Samples of ocean water, collected from exploration vessels and buoys, provide an incomplete record of ocean acidification, due to the limited number of readings available. This type of analysis is also expensive, making space-based observations a valuable tool for climatologists studying the problem.
Data from the Soil Moisture and Ocean Salinity (SMOS) observatory, launched by the European Space Agency (ESA) in 2009, as well as NASA's Aquarius satellite, were used to create the new map. The new chart is the product of combining measurements of salt content with thermal imaging, in order to calculate acidity.
The new map makes it possible for researchers to quickly identify regions of the world most impacted by the problem. Areas around the northeastern United States were shown to be highly acidic compared to most of the global ocean. Coastal regions worldwide were also found to be more acidic than areas with deeper water.
"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," Jamie Shutler from the University of Exeter said.
Shellfish, including oysters, clams and mussels, can see their shells damaged by rising acidity in oceans, potentially reducing their populations. This die off could be felt higher up the food chain, killing off large numbers of animals that usually feed on these species.
Concentrations of different forms of carbon were also examined in samples from around the world, and compared to total alkalinity. Comparison of these two numbers show how much of a buffer the water can supply to rising acidity. Research found this buffer was greatest along the southern coast of the United States, including the Gulf, and decreased with increasing latitude, becoming weakest in the waters off Maine. Researchers are uncertain why this relationship exists, or how it could be altered by global warming.
A study published in 2013 showed that fish act more skittish in acidic water than in normal oceans, which could potentially alter hunting and mating patterns.
Development of the new map showing ocean acidification around the globe was detailed in the journal Environmental Science and Technology.