Image showing total alkalinity from space

Satellite images reveal ocean acidification from space

Image courtesy of Ifremer/ESA/CNES 

Pioneering techniques that use satellites to monitor ocean acidification are set to revolutionise the way that marine biologists and climate scientists study the ocean. 

This new approach, published today in the journal Environmental Science and Technology, offers remote monitoring of large swathes of inaccessible ocean from satellites that orbit the Earth some 700 km above our heads.

Each year more than a quarter of global CO2 emissions from burning fossil fuels and cement production are taken up by the Earth’s oceans. This process turns the seawater more acidic, making it more difficult for some marine life to live. Rising CO2 emissions, and the increasing acidity of seawater over the next century, has the potential to devastate some marine ecosystems, a food resource on which we rely, and so careful monitoring of changes in ocean acidity is crucial.

Researchers at PML, the University of Exeter, Institut Francais Recherche Pour L´Exploitation de la Mer (Ifremer), the European Space Agency (ESA) and a team of international collaborators are developing new methods that allow them to monitor the acidity of the oceans from space.

Dr Jamie Shutler from the University of Exeter who is leading the research said: “Satellites are likely to become increasingly important for monitoring ocean acidification, especially in remote waters. It can be both difficult and expensive to take year-round direct measurements in such inaccessible locations. 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.”

Current methods of measuring temperature and salinity to determine acidity, though highly accurate, are restricted to in situ instruments and measurements taken from research vessels. This approach limits the sampling to small areas of the ocean, as research vessels are very expensive to run and operate.

The new technique use satellite mounted thermal cameras to measure ocean temperature while microwave sensors measure the salinity. Together these measurements can be used to assess ocean acidification more quickly and over much larger areas than has been possible before.

PML scientist Dr Peter Land, who is lead author of the paper, said: “In recent years, gre2010-2014 annual averaged alkalinity diagramat advances have been made in the global provision of satellite and in situ data. It is now time to evaluate these new data sources to help us understand ocean acidification, and to establish where remotely-sensed data can make the best contribution.”

A number of existing satellites can be used for the task; these include the European Space Agency Soil Moisture and Ocean Salinity (SMOS) sensor that was launched in 2009 and NASA’s Aquarius satellite that was launched in 2011.

The development of the technology and the importance of monitoring ocean acidification are likely to support the development of further satellite sensors in the coming years.

Image right: Total alkalinity from space (click image to enlarge). Red indicates higher alkalinity and, therefore more resilient to acidification than the blue areas, which highlight areas of lower alkalinity. Courtesy of Ifremer/ESA/CNES.

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