Analysis: How bottles helped scientists catch the drift

THE story of scientific drift bottles harks back to a time when we were only beginning to understand the complexities of the seas.

Such bottles were dropped into the sea by researchers trying to discover the flow of water in the North Sea – the long-term drift, and not the tide.

It was driven at the time by the interest in the herring fishery because herring lay their eggs on gravel and, when the larvae hatch, they drift with the current. The researchers wanted to know where the currents were taking the herring larvae, to help the fishing industry.

The conclusions of these pioneering oceanographers were right in many respects. They got the general flow of the North Sea – the long-term movement which is sort of anti-clockwise around the North Sea. It goes down the Scottish coast, along the European coast and up the Norwegian coast. They got that general circulation right.

The modern version of these drift bottles is the satellite-tracked drifter buoy. Every two seconds we know where they are. And now there are very sophisticated devices that can move along the seabed and pop up now and again and send their data back up to satellites. But it’s amazing that, nearly 98 years on, bottles are still being returned to the Marine Laboratory – and in such fantastic condition.

• Dr Bill Turrell is head of marine ecosystems with Marine Scotland Science.