A long-running study monitoring the ocean near Bermuda this month celebrated its 70th anniversary.

Hydrostation “S”, about 15 miles south-east of Bermuda, was first launched on June 7, 1954 by Henry Stommel, an oceanographer with the Woods Hole Oceanic Institution.

Since then, it has collected measurements of temperature, salinity, dissolved oxygen and other data every two weeks apart from a brief period more than 30 years ago when repairs were carried out.

The data collected has been used in more than 600 scientific publications and, together with the Bermuda Institute of Ocean Sciences’ Bermuda Atlantic Time-series Study, it provides the longest continuous record of warming water temperatures.

BIOS noted the hydrostation’s anniversary this week in it’s Currents newsletter.

Rodney Johnson, an ASU BIOS associate research professor and the station’s co-principal investigator, said: “To this day, we have the longest-running set of measurements in the open ocean in the world.

“The Hydrostation ‘S’ data clearly show significant long-term changes in ocean warming, particularly in the upper 500 metres.

“We were aware of it back in the Eighties, of course, but the message was a much harder sell back then.”

Readings from Hydrostation “S” showed that the average surface water temperature off the island was now 1C warmer than 40 years ago, while the surface waters have also gradually become saltier and 30 per cent more acidic during the same period.

While the hydrostation has been up and running for 70 years, data collection methods have evolved over time

The Currents newsletter said that when Mr Johnson first visited Hydrostation “S” in 1988, researchers used a “hydro wire” system to collect data using a series of bottles at different depths.

It explained: “Each bottle had a brass messenger weighing about a pound that would close the bottle once a water sample was collected, then descend to close the next sample and so on.

“Each bottle was also equipped with two reversing thermometers – one protected from ocean pressure and one unprotected.

“When each sample was completed, stems of the thermometers would snap off to record the temperature at that specific depth within a 1,000th of a degree.”

Researchers would collect the samples and use the readings from both thermometers to calculate the exact depth that the temperatures were taken, while noting the amount of dissolved oxygen and carbon dioxide, salinity, bacteria and nutrients.

The hydro line approach was replaced by a conductivity, temperature and depth device capable of collecting 24 water column samples per second.

Mr Johnson said that the location of the hydrostation near the island was beneficial to researchers.

“The wonderful thing about doing oceanography in Bermuda is we’re very close to that deep ocean. It gives us the flexibility to get in and out of storms,” he said.

The accessibility of the station has also paid dividends for students, who have taken research cruises to the station for a first hand look at science in action.

Nicholas Bates, the ASU BIOS director of research and principal investigator for the station, said: “Hydrostation ‘S’ cruises contribute to the first ‘at-sea’ experience of many students and to building interest and experience for students considering careers in marine science and Stem subjects.

“This is very important for improving the access of undergraduate and graduate students to the ocean and encouraging more students to pursue a career in science.”