I have taken quite a few pictures and now that the final week of the expedition is here, I’m already wondering what will my family and friends think when I show them the pictures. They will probably think that the scenery didn’t really change. Some days were less gray than others. Some days the grayness was replaced by whiteness. Some days the gray ocean was flat, some days wavy. Some days the ice was broken, some days there were clear turquoise stripes, some days the ice looked dirty. But unless you are an oceanographer, you are not likely thinking that there is something going on below the dark surface of the ocean. Yes, the ocean is changing from one location to other! You cannot see the change in temperature and salinity with your eyes but that’s what makes watching CTD (conductivity, temperature, depth) casts so fascinating.
For a 3000meters deep station, it takes about 2 hours for the CTD profiler to go down, and another 2 to get up. Okay, the way up looks quite similar to the way down, but still, there are 2 hours of excitement: how fresh will the surface layer be, how warm the Atlantic water layer, how thick the halocline? (Halocline means the layer where the salinity changes significantly with depth.) Here, close to the continental slope, another exciting feature is common: intrusions, or a zigzag pattern, in temperature and salinity, indicating that two water masses from different locations are meeting just below us. The zigzag pattern results when the two water masses have different properties, for example, when one is warm and saline (Atlantic water) and the other cold and fresh (water from this continental slope), but their density is the same. Because there is no density difference, neither of the water masses wants to be pressed below the other. Instead they try to intrude each other, thus the name “intrusion”.
In my recent research I have been assessing the variability and circulation of the Atlantic water entering the Arctic Ocean through the Barents Sea. This so-called Barents Sea branch of Atlantic water is colder than the other Atlantic water branch entering the Arctic through the Fram Strait, because over the shallow Barents Sea, the inflowing water is in contact longer with the atmosphere than in the narrow and deeper Fram Strait. North of the Severnaya Zemlya islands (off the north coast of Russia), these two branches meet and partly mix, which can be seen in the zigzag pattern in the temperature and salinity profiles. A later phase of the mixing process looks more like steps (like in the photo).
Although the lab is crowded when we are at the station and they don’t need curious students around, between the stations is a good opportunity to sneak a peak of the CTD profile. In addition, this oceanographer at the vegetarian table in the dining hall has also learned to memorize the properties of the recent profiles, so as to keep the other vegetarian students of oceanography up to date in what is going on below us. The thought of being on top of the water that you are studying, in the exact time and place when the processes are taking place just underneath my bed, gives me a whole different perspective to the profiles that I analyze back home.
- Meri Korhonen