On Saturday, we reached the eastern-most point of this expedition, just a few 10s of miles off the western coast of Scotland. We could almost hear the bagpipes ! Our Scottish colleagues, led by OSNAP principal investigator Stuart Cunningham, deployed the last of the moorings–a trawl-resistant frame with an acoustic Doppler current profiler, or ADCP, inside. This frame is like a protected cave for the ADCP. the top face has sloping sides so that when a fishing trawl runs into it, the trawl should just roll up and over the frame. The instrument stays in place and the fishers get their nets back intact. Everyone is happy. The ADCP meanwhile sends acoustic pings upward every three minutes, and from the Doppler (frequency) shift of the return echos, the speed and direction of the currents at all depths from the sea bottom (at 400 meters) up to the sea surface can be determined. The data are stored inside the instrument for a year, after which Stuart and his team will retrieve it and replace it with a new instrument that will monitor the currents for the second year.
This talk about data storage reminds me that what we are doing on this cruise is making an investment for a better understanding of the long-term climate of our one and only planet, Earth. On some oceanographic research expeditions, new discoveries are made on the spot. This is not one of those trips. Instead, we are putting in place the infrastructure to measure the strength of the ocean circulation and its heat and salt flux for, we hope, at least a decade. There are natural fluctuations in ocean currents over weeks, months and even years. In order to measure the impact of rising greenhouse gas concentration in the atmosphere caused by human activity, we have to make measurements for many yearsin order to “average out” the natural variations. Only in this way can we really see how the oceans are changing in response to the burning of fossil fuels.
Unlike some other scientific inquiries, the study of how our climate is changing will span multiple generations of scientists. My colleagues and I, and the scientists who have already started to try to understand climate changes, are just at the leading edge of what must be a sustained, multi-decade commitment. In the 10 or so years left in my career, I will hopefully see the first results coming from the observing system we are putting in place now with OSNAP. In two years time, the subsurface floats we are releasing on this cruise will re-surface and tell us where they have traveled. This will be but one piece in the complex puzzle that is the Earth’s climate system. We hope that the half dozen students out here on the Knorr with us now will be inspired to carry on with this important work.