Argo floats, such as this one deployed from a French vessel, have produced valuable oceanographic data but new techniques are needed to track changes in the world's oceans.

Argo floats, such as this one deployed from a French vessel, have produced valuable oceanographic data but new techniques are needed to track changes in the world's oceans.

ARGO

New sensors promise better picture of world ocean health

TOKYO–Marine scientists are developing new sensors they plan to deploy in a global monitoring system to better observe changes occurring in the world’s oceans. 

“In some ways we know more about Mars than our own oceans yet they do govern everything from regional climate to economics,” said Karen Wiltshire of Helmholtz, Germany’s Alfred Wegener Institute for Polar and Marine Research. Wiltshire, chair of the Partnership for Observation of the Global Oceans (POGO) presented the new observational strategy at a press conference here today ahead of the annual meeting of the partnership, which brings together 40 oceanographic institutions. The goal is to have the new global monitoring system in place by 2030.

Since it was founded in 1999, POGO has coordinated the worldwide deployment of some 20,000 autonomous probes known as Argo floats that gather temperature, salinity, and current velocity data. Ten percent also have oxygen sensors. The probes go up and down a water column to a depth of 2 kilometers and relay data by satellite link when they surface. The data is publicly available within 24 hours. The probes last 2 years, and approximately 4000 are currently active.

The researchers said that while Argo has transformed ocean observation, there is a greater need for more and better data. “The global ocean observing system has become stalled; it is not progressing at the rate that is necessary,” said Ed Hill, executive director of Southamption, Britain’s National Oceanography Centre. He added that scientists need to monitor carbon storage and possible temperature increases in oceans at depths greater than 2 kilometers in addition to adding biogeochemical sensing capacity.

“For example, [measuring] chlorophyll a will give you information about how much biological activity is going on, and eventually more information about the concentration of carbon dioxide within the ocean and the atmosphere,” said Yoshihisa Shirayama, executive director of research at the Japan Agency for Marine-Earth Science and Technology in Tokyo.

To gather this information, researchers are developing sensors to measure seawater carbon content, acidity, the concentration of nutrients such as nitrates and phosphorous and even gather genomic data.

A new generation of sensors could be adapted to a variety of platforms including coastal moorings, current drifters, undersea Internet cables, oilrigs, and ships. Optical sensors installed on ships, for instance, can determine ocean water color that reflects the activity of micro-algae at the bottom of the food chain and, when examined alongside satellite color observations, can support extrapolations about what’s happening in a given area of ocean. “The more you measure with a small device over large distances, the more information you have to calibrate your satellite information,” Wiltshire said.

Some of the sensors are operational and are being gradually put into use. Others, such as acidity sensors, are only coming out of labs now. “The common thread is that the technologies to do this without having to collect big buckets of seawater are starting to come on stream,” Hill said. “The goal is not just realistic, it’s a must,” said Wiltshire. “It’s absolutely imperative for this planet."

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