Scientist Penny Holliday recalls being waylaid by world record waves while working in the North Atlantic.
We had been expecting awful weather. The statistics showed how bad conditions were likely to be during a winter cruise in the North Atlantic aboard the RSS Discovery , the biggest of the Natural Environment Research Council's vessels. However, what we experienced in February, no more than 250 miles off the Scottish coast, was beyond our expectations. I love hearing salty old sea stories. Now I have been in one.
We set sail from Southampton on January and steamed through the Irish Sea to Dunstaffnage, near Oban, to bring our complement of scientists to 25. It was windy but sheltered around the Hebridean islands, and we were able to do several days' work, gradually heading from Barra Head, along the continental shelf and into the open ocean.
Instruments to measure salinity, temperature and other properties of the water were lowered over the ship's side, while other instruments left on the seabed during earlier expeditions were recovered. Since 1975, the area around the Rockall Trough, northeast North Atlantic, has been surveyed several times a year in a long-term ocean monitoring study. Only by continually revisiting the region will we learn if the ocean currents and water temperature west of the United Kingdom are changing due to global warming.
The winter is a particularly important time of year here, when deep mixing in the upper ocean releases into the atmosphere heat stored there over the summer, helping to keep northern Europe mild. This mixing is convective, like the kind of motion that occurs in a pan of boiling water, only in reverse. In the Rockall Trough, cold air "removes" heat from the water, which then sinks and is replaced by warmer water from below and so on.
As we headed out beyond the continental shelf, the winds began to pick up. For five days conditions were dreadful, with winds up to storm force 11 as a series of four tight depressions raced over us. We kept thinking that we would get calm periods between the depressions when we could do some work, but the weather never let up.
The oceans are amazing to watch when the wind is that strong. The surface of the ocean gets completely whipped up, and there is so much spray it looks as if it is snowing. We watched in awe as the enormous waves built up. The scariest bit is when you are at the top, looking into this enormous hole in the sea below. You imagine the ship might just continue down and not come up again. We had an instrument called a ship-born wave recorder that measures the attitude and the vertical motion of the ship. It has an output in the main laboratory, and there was quite often a crowd of us around it. Our biggest wave was 29m, the height of the Southampton Oceanography Centre and 3m higher than the one in The Guinness Book of Records .
At the height of the storm at 4am, our starboard lifeboat came loose, swinging freely. It repeatedly slammed against the side of the ship, waking everyone. Crewmen had to brave the waves to secure it.
In such conditions you cannot work because you cannot go on deck. We just had to sit and hope the weather would change. People played cards, read books, tried to finish writing papers or complete data analysis - but it is hard to do anything because you are literally being flung around. You have to tie yourself to your chair to even attempt to work.
We have a lot of safety training, and everyone has confidence in the ship, its officers and its crew. However, some people got a bit freaked by the whole thing, and a couple sustained broken ribs after falling.
After five days, we realised the weather was not going to change so we turned around and surfed the waves back to Barra. We completed perhaps only a quarter of the deep ocean work we had intended to do, though this revealed a winter water temperature higher than it has been for the past 25 years. Those huge waves were the unexpected result - I am now preparing a paper with a colleague on it. Nevertheless, it was disappointing from a scientific perspective, though there was real relief and a feeling of achievement in just surviving.
Penny Holliday is a project scientist at the Southampton Oceanography Centre and was co-chief scientist on the RSS Discovery's cruise to the Rockall Trough in January/February. She hopes to return to the area in the spring.