The man with the ocean in his laptop

When other people stand on Borkum’s shore and look out at the water, they see nothing but the blue of the North Sea, waves and the vast water. They take a deep breath and just enjoy their vacation. But even on vacation, Nils Christiansen’s eyes search for the wind turbines, just visible as small silhouettes on the horizon. When he stands on the beach and looks at the waves, the 31-year-old thinks about wind speeds, changes in air and water currents, and the question of what the 4,500 or so wind turbines that humans have placed in the North Sea are doing to the marine ecosystem.

Even as a child, Christiansen regularly spent time on the island; he and his family always came up from Bielefeld for vacation. Today, he travels to Borkum once a year, but the North Sea accompanies him every day in his work at the Institute for Coastal Systems, part of the Helmholtz Center Hereon in Geesthacht. “I look at what happens when you put a wind farm in the ocean,” says Christiansen, trying to explain his complex work. “I simulate the North Sea on my laptop using a numerical model and add mathematical equations to represent the wind farms. This allows me to see how the ocean currents change due to influences in the atmosphere and underwater – in a digital aquarium with wind farms, so to speak.”

For most non-experts, a wind turbine is a huge machine that, at best, produces electricity as efficiently as possible, but nothing more. But Christiansen knows from his research how dynamically the large wind turbines interact with the environment and what physical forces are at work: the wind pushes at the ocean, causing waves to form. This is particularly true of the North Sea. But wind turbines intercept some of the wind energy – or, as Christiansen puts it, “They suck energy out. So you have less energy behind the wind turbine, which in turn has an effect on the sea’s surface.” There’s also another effect: wind turbines create resistance for water currents. In Christiansen’s words, “It’s just like when you put your foot in a stream. Then the current has to flow around your foot, swirls around behind the obstacle, and slows down.”

Ultimately, a wind farm in the North Sea has two effects: it changes the flow of air and the turbulence in the water. In turn, these two factors influence the transport of nutrients in the sea, the mixing of the individual water layers, and with it, the productivity of the phytoplankton. As such, here physics and biology are directly linked. “The surrounding ecosystem, whether for a single wind turbine or an entire offshore wind farm, adapts to the physical changes,” says Christiansen. “It’s super-complex, but also super-interesting!”

The aim of his ongoing research is to find out how these changes affect the food chain. “But we’re not there yet,” says Christiansen, who collaborates closely with a colleague from ecosystem modeling in his work. Scientists have only been focusing on offshore parks as a research topic for a few years. However, with the expansion of renewable energies, the need for scientific data is growing: to date, Germany generates roughly nine gigawatts of offshore wind energy every year – and the figure is set to rise to 70 gigawatts by 2045.

Christiansen wants to better understand the exact changes caused by offshore farms in order to more accurately assess the impact of human activities on the marine ecosystem. For example, his research suggests that the distance between the individual wind turbines in an offshore wind farm plays a decisive role: he surmises that if the individual turbines are further apart, the overall effect on the surrounding ecosystem is reduced. For new wind farms still in the planning stage, this could mean that fewer but more powerful turbines per wind farm will be built in future.

Further, Christiansen isn’t just concerned about his ecological footprint professionally, but also privately. As he himself says, he’s the kind of person who always thinks very carefully about the consequences of their actions. As such, the guiding question in his private life is the same: what impact does it all have?

Therefore, he decided years ago to fly as little as possible. He’s a vegetarian. And when the weather permits in summer, he chooses the most climate-neutral means of transportation and cycles to work at the institute. “If these choices reduce my personal footprint, I’m happy to do it,” says Christiansen, without sounding preachy.

Nature is important to him, and always has been. Even as a young boy, it fascinated him. His enthusiasm for science was also there early on. “Although I still wanted to be a professional athlete at the age of six,” he says. After leaving school, Christiansen initially followed his passion for sports, but studying sports science didn’t pan out; an injury got in the way of the entrance exam. Christiansen ended up studying geophysics “because the subject combines my interest in nature and my natural talents. It’s also very practice-oriented.” By the age of 26, Christiansen had completed his Bachelor’s and Master’s degrees in Münster and went to Hamburg for his doctorate. Last year, he was awarded the Kurt Hartwig Siemers Science Prize and the Helmholtz Doctoral Prize in the field of Earth and Environment for his outstanding scientific achievements in his dissertation.

Both prizes mean a lot to him, says Christiansen. He is the first person in his family to have studied and even completed a doctorate, an educational climber. Though his research career has only begun, so far it looks extremely promising – and the same is true for his research subject, the wind farms in the North Sea.