unizeit Schriftzug

Ocean currents in a water tank

Those who want to make accurate weather and climate predictions must have one thing above all else: an understanding of mathematics. Because bone-dry equations form the basis of all climate processes. In order to liven up his teaching, meteorologist Dr Torge Martin relies on wet experiments, with the support of PerLe funding for innovative teaching.

Colored clouds in a rotating water tank
© pur.pur

How will the added dye solution mix? Will a red cloud form or rather a column when turning?

What will the weather be like tomorrow? What climate changes must we face during this decade? These are questions tackled by meteorologists as well as oceanographers, among others. "However, in order to really understand climate processes, to calculate the path of high-pressure and low-pressure areas, or to predict temperatures for Kiel and the rest of the world, the students must first understand and internalise the basics of the global movement of air and water masses, and their impact on the weather," explained Dr Torge Martin from the GEOMAR Helmholtz Centre for Ocean Research Kiel. This takes place during the Bachelor's degree programme in Physics of the Earth System at the CAU.

Learning the basics means nothing other than the students having to deal with a lot of mathematics and physics. For example, how the warm Gulf Stream in the Atlantic moves forward, how fast the water flows, how the circular or swirling movements of water masses arise, and what that means for the temperatures on land - all of these are explained using mathematical equations. And in the complex global contexts, they are not easy to grasp. "For a better understanding, each phenomenon is broken up into smaller units and explained, like for example the emergence of a vortex - a so-called eddy - in the Gulf Stream," explained Dr Martin. But this doesn’t change the fact that his exercises - with which he supplements the lectures given by Professor Arne Biastoch - are often very theoretical.

Two students in a laboratory
© pur.pur

Using the pipette, Christiane Lösel (left) and Ludwig Bitzan add color solution drop by drop into the rotating water tank. How the liquids mix depends on the rotation of the tank, as the students were able to find out from the experiments. Practical knowledge helps to understand dry facts.

In order to provide a better understanding for the students, but also to make the topic more fun and awaken curiosity, the meteorologist together with the oceanographer Dr Mirjam Gleßmer are daring to try something new this and next semester: "We want to make the basics of water movements tangible and better understandable, with practical experiments in water tanks and on the computer." For this purpose, after initial experiments in his kitchen at home, he obtained rotating trays and placed tanks of water on top, measuring around 35 centimetres in diameter. A small LEGO Technic motor drives the tray, and simulates the rotation of the earth. With coloured dye, added drop by drop, the students can test how a vortex arises in the rotating system. And how the mixing of the dye looks, if the tray is stationary. The teaching project is funded through the Quality Pact for Teaching of the Federal Ministry of Education and Research (BMBF), through PerLe funding for innovative teaching.

The first lesson was already very exciting, reported Martin, who himself "really enjoys playing with water and designing experiments." Instead of frontal instruction, there was interactive work in small groups, who tested with a great deal of enthusiasm whether the rotating trays could also be driven by hand ("no, the speed is not consistent enough") and whether pots or vases are suitable for these experiments as an alternative to the tanks ("no, they are inadequate"). If the tray and with it the water are stationary, the dye dripped in distributes itself in the water like a cloud, "similar to cream in hot tea," said Martin. On the other hand, if the tray is rotating evenly, a vortex arises - similar to the eddies in the Gulf Stream. "In order to explain this difference, there is a formula, the Taylor-Proudman theorem. And it is easier to understand when you have created the vortex yourself," he said with conviction. In any case, the students really enjoyed the different way of teaching. The exercises will remain mostly theoretical - "at the end of the day, the students are expected to pass their exams" - but further experiments should follow. So that other students can also benefit, there is a digital documentation of the experiments in the project's own blog.

Author: Jennifer Ruske

Further reading: www.oceanblogs.org/teachingoceanscience