Setting sail for the high seas!

Rieke Schäfer studied marine science. This is something that you don’t necessarily expect for someone working at PTB, where you are more likely to meet researchers from the realm of measurements in physics and engineering. “Well, I studied biomimetics first, with a focus on sensors and measurement. That sounds more like something you’d find at PTB,” laughs the young scientist. Biomimetics is that branch of engineering that takes its inspiration from nature. And what inspired the young Rieke Schäfer – who grew up on the coast in Bremerhaven – were fish. To be more exact: fish and their lateral line organs; the organs that they also use to detect the movement of waves. So going on to become a marine scientist was just a short step. Rieke Schäfer chose to do her master’s degree in an unusual place: the Orkney Islands in the very north of Scotland. The Heriot-Watt University based in Edinburgh has a campus there. “And that was in the middle of the pandemic – it was just us with the wind and the waves,” she says. All things considered, this means she is very well prepared for her next helping of wind and waves that will be even more extreme – her upcoming voyage from this April to June.

When her PhD supervisor Eric Achterberg (from the GEOMAR Helmholtz Centre for Ocean Research in Kiel) and Steffen Seitz, her advisor from PTB, asked her if she’d like to set sail with the research vessel Sonne, she didn’t hesitate for long and said yes almost straightaway. Going on this voyage will mean she’ll be able to add another section to her doctoral thesis. In addition to the highly accurate determination of the pH, as carried out at PTB, she will now include material on how the pH is measured in practice, how instruments are calibrated, what effects this has on measurement uncertainty, and how all this can be made more accurate.

Meanwhile, her colleagues on board are going to be working on some very different fields of research. Most of the fellow members of the expedition, who are from a variety of German research centers, will be concentrating on measuring trace elements, such as heavy metals, in the ocean. They are part of GEOTRACES, an international research project, that has been studying the biogeochemical cycles of trace elements and their isotopes in the marine environment since 2010. They have, for example, already found out that the Congo River delivers a large amount of iron into the ocean (more than the Amazon). That is good for phytoplankton and thus also benefits the fish population in the Atlantic, but this process is being endangered by climate change. GEOTRACES’s researchers have also found out a great deal about the (declining) lead concentrations of the oceans.

Each voyage on an expensive research vessel is also used to perform standard measurements that are needed again and again over many years. What is important here is finding out about climate change and its effect on the oceans, but understanding the marine environment better in general is just as crucial. Temperature, salinity and the pH are some of the parameters that are measured. The latter has clearly been falling since the industrial revolution began. This is being caused by an increase in one of the main greenhouse gases, CO₂, in the air. As the amount of CO₂ in the air and in water is always kept in balance, more CO₂ is being forced into water, forming carbonic acid and making the water more acidic. But acids also damage corals and other marine organisms that form coral reefs or that store calcium carbonate in their bodies (such as shellfish do in their shells). Something that initially sounds good for us people – CO₂ disappearing from the air – actually damages marine animals. And there is also the additional damage caused by the rising water temperature to be considered.

The pH has to be measured continually and as accurately as possible so that we can understand the whole system more exactly and counteract the damage effectively wherever possible. Rieke Schäfer will also be tasked with this between April and June 2023. The research vessel Sonne is going to set sail from Guayaquil (Ecuador) on 14 April 2023. Its course will take it many thousands of kilometers to the west along the equator. The Sonne will eventually steer south and dock in the Australian city of Townsville on 2 June 2023. PTB, and anyone else who wants to, can accompany her by following the Expedition Blog. es/ptb

You can find the Expedition Blog here