In the past few years, the oceanographer has focused his efforts on identifying which forces make the Atlantic water from the West Spitsbergen Current veer off west – because, upon closer inspection, the physics of seawater are highly complex, with their fair share of apparent contradictions. His favourite example is that, on their own, different water masses don’t actually mix. As the AWI researcher explains, “The temperature and salinity differences between any two water masses create layers and fronts that are hard to break through. As a result, within a given current, the water basically flows just as if it were in a pipe. Normally, it shouldn’t be able to veer off to the left or right.” Nevertheless, AWI scientists have observed water masses splitting in the Fram Strait. “That’s possible because of eddies in the West Spitsbergen Current. They are several kilometres wide and several hundred metres deep, sometimes even extending down to the seafloor,” says Wilken von Appen.
And their spinning motion makes the water fronts unstable. “For one thing, we know this produces the westward flow in the Fram Strait. Yet we also believe the same mechanism to be the reason why the warm and dense Atlantic water manages to slip below the ice-cold water in the East Greenland Current.” The computer models created by his AWI colleagues Dr Claudia Wekerle and Dr Tore Hattermann allow Wilken von Appen to see what these eddies most likely look like. But tracking them down in the open sea to confirm the team’s hypothesis is quite a different challenge. “As part of the AWI’s major infrastructure initiative FRAM, in the summer of 2016, we installed new moorings at exactly those points where the model estimates part of the Atlantic water turns off to the west. We currently assume there are two such turning points, but we still need observational data for confirmation,” explains Wilken von Appen.
If only retrieving that data weren’t so nerve-wracking. It’s now been a minute and five seconds since the signal was transmitted. Suddenly, the officer on duty calls out, “Buoys in sight,” and points toward a pair of ice floes drifting alongside the research icebreaker. Wilken von Appen breathes a short sigh of relief, then switches his routine to autopilot: Make a written record of the retrieval, clean the measuring equipment, transfer and check their data, maybe even glean the first scientific insights – his work schedule for the next 48 hours is already full. And that was just the first of more than 20 moorings!
Text: Sina Löschke