Using Satellite Imagery to Track the Ocean’s Acidity

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The Earth’s oceans play a vital role in the health of the planet. Ocean dynamics impact weather patterns, it provides food and recreational opportunities, and industry related to the ocean generates significant revenue. The ocean also serves a critical function in regards to easing global warming, and scientists are now using satellites in order to better understand the impact of carbon dioxide on the acidity of the ocean.

Seawater helps to combat global warming by absorbing some of the carbon dioxide that humans release into the atmosphere, mainly from the burning of fossil fuels. Instead of hovering in the atmosphere, about a quarter of greenhouse gases are soaked up by the ocean. When seawater does this, however, its acidity increases. Upsurges in acidity are causing some concern among scientists because of the potential effects on ocean life as well as the global economy.

According to the National Oceanic Atmospheric Administration (NOAA), the ocean’s surface pH has become 30 percent more acidic since the Industrial Revolution. The acidity of the ocean is not easy to measure nor is it evenly distributed. Plus, past attempts to monitor the pH balance of the ocean have involved research vessels and buoys which are expensive and unreliable.

This is where remote sensing comes in. Scientists are now using satellites in order to monitor large areas of the ocean and identify those that are most at risk from acidification. Researchers at the University of Exeter in the United Kingdom took it one step further, developing a map of the ocean’s acidity that displays which areas are most impacted.


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To produce this map, researchers used satellite imagery from NASA’s Aquarius satellite as well as the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite. Thermal mounted cameras on the satellites measure the temperature of the ocean while microwave sensors measure its salinity. Both of these readings can then be employed to evaluate the acidity of the ocean over larger areas in a shorter amount of time than before.

The map created from satellite measurements displays how much the ocean varies in acidity. Areas that are reddish in color are more alkaline or basic, and this means that they have more room to absorb carbon dioxide floating in the atmosphere. It appears that open regions of the ocean are more resilient to becoming excessively acidic while coastal areas are more vulnerable. The northeastern U.S. is particularly susceptible, and this could have important consequences down the road.

The map created from satellite measurements displays how much the ocean varies in acidity. Areas that are reddish in color are more alkaline or basic, and this means that they have more room to absorb carbon dioxide floating in the atmosphere.  Image: Ifremer/ESA/CNES

The map created from satellite measurements displays how much the ocean varies in acidity. Areas that are reddish in color are more alkaline or basic, and this means that they have more room to absorb carbon dioxide floating in the atmosphere. Image: Ifremer/ESA/CNES

Scientists are concerned about the increase in the ocean’s acidity because of the potential impacts on marine life. Higher acidity could make it more difficult for marine life to live. Acidification degrades the shells of oysters, mussels, and crabs. Baby oysters are already are disappearing from some areas, and the effects of this could be seen further up the food chain. There are also concerns about non-shelled marine life in that fish kept in acidic water act more skittish than those in normal seawater. Since the ocean is a major supplier of food, the monitoring of its acidity is more important than ever.

References:

Land, Peter E., Jamie D. Shutler, Helen Findlay, Fanny Girard-Ardhuin, Roberto Sabia, Nicolas Reul, Jean-Francois Piolle et al. “Salinity from space unlocks satellite-based assessment of ocean acidification.” Environmental science & technology (2015). Retrieved from: http://pubs.acs.org/doi/abs/10.1021/es504849s

“Global Ocean Acidity Revealed in New Maps.” http://www.livescience.com/49831-maps-reveal-ocean-acidification.html

“Satellite Images Reveal Ocean Acidification from Space.” http://www.exeter.ac.uk/news/featurednews/title_435490_en.html

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