The world’s oceans do far more than support vital marine ecosystems and provide food and recreation. They help regulate the Earth’s climate, absorbing vast amounts of heat and CO2, acting as one of the planet’s most important buffers against climate change.
Yet despite this vital role, scientists still struggle to track exactly how and where the ocean absorbs and stores CO2 – and how that process is changing.
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Rintala is leading an international team that aims to extend ocean observing capacity by developing sensors for platforms that can operate beyond normal shipping routes and deep below the surface – far from ships and human intervention
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At the heart of the effort is the development of the world’s first autonomous sensor capable of accurately measuring total alkalinity in the ocean – from the sea floor to the surface.
Total alkalinity is a key chemical indicator that scientists use to understand the ocean carbon system and estimate how much CO2 seawater can absorb and store.
It is also critical for tracking ocean acidification – a process driven by rising CO2 levels that lowers seawater pH and threatens marine ecosystems, particularly shell-building plankton and molluscs.
“Ocean acidification is very harmful for many marine organisms,” said Rintala. “It can cause cascading effects that ripple up the food web.”
Until now, total alkalinity has usually been measured by collecting fixed seawater samples from ships and analysing them later in onshore laboratories. That approach provides valuable data, but only at isolated points in time and space.
“If we are interested in the carbon content of the ocean as a whole, we need to measure deeper,” said ocean scientist Socratis Loucaides, based at the UK’s National Oceanography Centre (NOC).
Loucaides and his colleagues at NOC are leading the development of a radically different approach: a compact lab-on-a-chip sensor that performs a miniature chemistry experiment inside the instrument itself.
Inside the device, a small seawater sample is mixed with an acid of known strength and a dye that changes colour depending on acidity. A light-based sensor then reads those colour changes to calculate the alkalinity of the surrounding seawater.
By doing this directly in the deep ocean, the sensor can build up a far more detailed picture of how carbon is stored and transported over time – and potentially reveal early warning signs of change.
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