by Penny Holliday
Yesterday was one of those days when I was asking myself “Why am I here?”. Not exactly an existential crisis, but more a feeling that there was a possibility that coming to sea was not such a good idea as it had previously seemed. I was, of course, suffering from seasickness.
It turned out that I was not alone. There are a few lucky folk who don’t get sick when the weather picks up, but there were not many scientists to be seen around the labs yesterday as the sufferers sought refuge in pills, patches or just lying down. Being seasick can make you staggeringly tired, even without the drowsiness-inducing medication. I think I dozed almost all of the day and still slept all night.
We had run into strong winds and substantial waves as we headed away from the shelter of Northern Ireland and into the open ocean. We are making our way to Iceland to start the survey, and the alternative was to find shelter from the storm inside the Hebrides. That would have meant a fairly long detour and time lost so the decision was made to just head out. Today, with our sea-legs well established, it is clear that was a good call as we left the worst of the storm behind us, and have been making good progress. We should be in place to start work tomorrow night.
So this seems a good time to explain why we are here – and it’s not just because I thought it was a good idea when I was planning this in the non-moving environment of my office. I’ve mentioned before that this is the 40th year that we have been coming back to this section to measure the temperature and salinity of the ocean currents. The reasons this part of the ocean is so interesting comes down to two things: the first is that the warm ocean releases heat to the air above and that air blows across Europe, keeping us warm compared to countries at the same latitude west of the Atlantic Ocean. The second is that deep down below the warm surface layer is a massive river of cold, dense water flowing in the opposite direction. The warm upper 1000m of the ocean is drawn northwards into the Nordic Seas and eventually the Arctic Ocean, cooling all the while. The cold river below is the end result of all that warmth being given up to the atmosphere; the water eventually becomes so cold that it sinks, fills the bottom of the deep ocean basins, and spills over the top of a rocky dam between the Nordic Seas and the North Atlantic.
I’ve tried to illustrate what this looks like in the cartoon below. The orange-yellow-green arrows are the warm layer heading north in different currents, the dark blues are the cold layer heading south. Through the work of these massive currents, the ocean is redistributing heat around the world, and this makes them important players in our climate system. If they change the amount of water they carry, or they become warmer or cooler, then they alter the amount of heat found elsewhere.
The Extended Ellett Line was started 40 years ago specifically so that decades later we can look back and see how things have changed over time. And it really does take decades of measurements to see changes to our climate system. Later on in the blog I will describe the changes we have found and what they mean. Meanwhile, the joy of getting over seasickness makes you appreciate the beauty of the ocean, and the value of the research cruise even more.
Images by Penny Holliday