Changing system
29 January 2021, by RTG 2530
How do salinity, temperature and suspended matter change in the Elbe estuary within 24 hours? Several short videos created by PhD student Laurin Steidle with the help of data from the Federal Waterways Engineering and Research Institute (BAW) give answers.
The changes are immediately visible in the first few seconds of the video: slowly, the colour of the river changes from blue to green and yellow, and then turns dark blue again. The water body depicted is the Elbe, and the colour change illustrates the concentration of suspended matter over a period of 24 hours. When the river appears blue, between 0.2 and 0.3 kilogrammes of suspended matter per cubic metre (kg/m3) are in the water; when it’s yellow, it’s 0.6 to 0.7 kilogrammes per cubic metre. Steidle created several such videos, one shows the change in temperature, the other the salinity in the Elbe estuary.
"Overall, the videos show how much the Elbe estuary changes in 24 hours. During this period, the tide flows into the estuary twice," says Laurin Steidle. He started as a doctoral student in Research Training Group 2530 in November 2020 and created the short videos. "I got the data from the Federal Waterways Engineering and Research Institute to get an overview of the ecosystem," he says. "You need some practice to write the programmes or scripts with which the data can be visualised." The next step is to interpolate the data, which means missing measurements between two known points are calculated to create a coherent model.
From physics to biology
Laurin Steidle will be creating many more models over the next three years during his doctorate: In his project "Ecosystem modelling to assess carbon fluxes in estuarine channels" he will develop ecosystem models to analyse carbon fluxes in estuaries under the supervision of Prof. Dr. Inga Hense. The focus will be on how interactions between living organisms (bacteria, algae and animals) influence carbon fluxes in estuaries. Laurin Steidle describes the videos as technical preliminary studies; for his doctoral project he will use data collected by other doctoral students in field experiments in the estuary over the coming years.
The 28-year-old studied physics at the University of Vienna and worked a lot with numerics, a branch of mathematics. Numerical mathematics deals with the construction and analysis of algorithms for mathematical problems that are implemented with computers. The task is to reproduce, predict and control complex processes in nature and technology with the help of computer simulations.
Models must be reliable
He is particularly interested in the topic of earth system modelling because it is politically relevant. "You can only argue and make predictions if the models are reliable. That makes the subject very attractive," he says. "Methodologically, the projects I worked on before were very similar." So Steidle can already create the first small-scale modelling - as seen in the videos - at the beginning of his doctorate, even if he was previously at home in a different area.
He applied for the doctoral position because he wanted to gain experience and work in the field of modelling. Working in the Research Training Group has many advantages for him: "It's exciting to do research on a common topic with different doctoral researchers," he says. "The Research Training Group is like a hub, you can network, exchange know-how, even get involved in individual projects and contribute to the development of solutions. This is especially true for my field of modelling."
Visualisation of the temperature change in the Elbe estuary within 24 hours:
Visualisation of the change in salinity in the Elbe estuary within 24 hours: