No one who has seen pictures of the Arctic can deny the change

2 September 2019, by Ute Kreis

Photo: K. Saint Pere

Several new professors have been appointed at the Department of Earth Sciences – also with funding from the Excellence Strategy. Here we are introducing the new colleagues. Today: Dirk Notz

Mr Notz, you are a cryosphere expert, with a particular interest in sea ice. What does that involve  and why is it important for the climate?

The cryosphere is a collective scientific term for all the Earth’s ice, including ice sheets as well as permafrost and sea ice. My specialist area is sea ice, which forms at the water surface at sub-zero temperatures, and covers the majority of the ocean in the polar regions. It’s interesting because sea ice is one of the most important indicators that our climate is changing. We often read in the newspapers about record minus temperatures. But more important than the annual minimum – which in the short term also depends on the weather – is the fact that since the beginning of satellite observations forty years ago, the sea ice has shrunk considerably. That’s no longer the weather; it’s a long-term trend, a clear change in the climate.

Many people are fascinated by the Arctic and Antarctic, and the discovery of these last untouched spots on the map. How did you discover your passion for this topic?

As a meteorology student – in Hamburg by the way – I spent a year in the far north, on Spitsbergen, and I later taught at the University Centre Svalbard there. This is where I developed my love for this absolutely unique and beautiful area. Later, I also spent some time at the University of Washington in Seattle, and my doctoral thesis in Cambridge was on heat and salt transport in sea ice.

Did you have any “polar bear encounters” on your expeditions?

Yes, as a matter of fact, on our research trips in Svalbard it’s my job to make sure that none of the students are attacked by a polar bear. When we’re working outdoors we always need to have a gun with us, and also take part in firearms training beforehand. Luckily, there haven’t been any serious incidents so far. But sea ice research is exciting enough without this. It’s a relatively new research area, which has only been around to any great extent since the 70s. A lot of fundamental questions still need to be addressed and we often enter unchartered scientific territory.

Indeed, as a result of climate change your research subject could disappear completely – at least in the Arctic summer, couldn’t it?

Yes, the loss of sea ice is dramatic and it’s closely linked to the amount of CO2 that we humans release into the atmosphere. And we can even extrapolate this: In order to melt the remaining sea ice cover in the Arctic, we would need about 800 billion tonnes of additional CO2. We are currently emitting about 40 billion tonnes. On top of that there are the natural fluctuations, which means that, depending on future actions, we could experience an ice-free Arctic Ocean in summer, very, very soon.

What will you be doing at the university’s Cluster of Excellence “Climate, Climatic Change, and Society” CLICCS?

I’ll be working on a project involving the carbon cycle in the Arctic. Not just the CO2 in the air, but also the amounts released when the warmer climate leads to the permafrost thawing. Where does that CO2  go, and what happens to the heat? Until now, we have considered the sea ice as a sort of lid that doesn’t let any greenhouse gases into or out of the ocean. According to recent experiments in our ice laboratory in the Geomatikum, the sea ice could be more permeable than we thought.

Until recently, you headed a research group at the Max Planck Institute for Meteorology. As a professor, you will now be entering into teaching as well. What will change?

I’ve always enjoyed working with students – because completely new questions and perspectives are constantly arising. Theories, observations and climate models – I intend to include all of this in my teaching. For example, I plan to follow the MOSAIC Experiment, in which the research vessel  “Polarstern” will drift through the Arctic with the sea ice for a year. We will share data with the researchers, conduct experiments in the lab and develop a suitable computer model. It’s important for me that I give the students a sense of how science works and that expeditions and work at the computer back at home both have their place.

Despite the fact that we’ve known for several years that our climate is changing, little is being done and CO₂ emissions are continuing to rise. Isn’t that frustrating for you as a climate researcher?

I’m constantly trying to bring about change. Communicating climate change and its consequences is my hobbyhorse. I give lectures and interviews, and I take the topic into schools and businesses. Sadly, the rapid melting is an advantage here: No one who has seen pictures of the Arctic – current and from 30 years ago – can possibly deny the change.