Aimée Slangen
The sea level is rising due to climate change. But how exactly does this work? And does it rise equally in all parts of the world? Climate scientist Aimée Slangen from the Royal Netherlands Institute for Sea Research (NIOZ) is mapping regional sea level rise to make more accurate assessments of the risks for each area.
‘My research on sea level rise is a whodunnit.’
What are you researching?
We tend to think of the oceans as one large, flat mass, but in reality, it's more like a hilly landscape: in some places, the sea level is several meters higher than in others. This is due, among other factors, to the shape of the Earth, the density of the water, gravity, and land subsidence.
The Earth is not perfectly round but rather like a slightly dented orange. The Earth's crust pushes the water higher in some areas than in others. Additionally, oceans either shrink or expand depending on temperature and salinity. Sea levels are lower in cold, salty areas than in warm, fresh areas because the water molecules are more tightly packed in colder water.
Gravity also causes variations in water height. Areas with a lot of mass, such as the ice sheet over Antarctica, attract water. When that ice sheet melts, more water enters the ocean. However, it also spreads over a larger area. As a result, gravity in the South Pole weakens, and sea levels rise on the Northern Hemisphere. Finally, factors such as earthquakes and groundwater extraction cause the ground to sink. When the ground sinks, the net sea level rises.
How did you get here?
I started with a broad focus on climate during my studies in "Soil, Water, and Atmosphere" at Wageningen University. Later, for my PhD, I was the first researcher to investigate the impact of melting glacier ice on regional sea levels, rather than looking at the global average sea level.
In 2017, I continued this work at the NIOZ, and a year later, I was selected to contribute to a United Nations IPCC report. Along with twenty other authors, I helped write a 120-page chapter on oceans, ice, and sea level rise. I am particularly proud of the sentences I was able to add to the summary of the report afterward. Countries from all around the world wanted to know more about it.
What does your research look like?
I am one of the few at NIOZ who works solely with computers, using climate models and, for example, satellite measurements. Currently, I am investigating the causes of regional sea level rise in the twentieth century. How much of it is due to temperature increase, land subsidence, melting ice, etc., and how much of it is caused by humans? We actually don’t know that very well. It’s also challenging to research because the further back we go in time, the less data we have. And since you have to bring together various different processes, there isn’t a single model that can calculate sea level rise.
Why is your research important?
By understanding the past, we hope to improve our future projections so we can identify which areas are most vulnerable to sea level rise. For this, the entire ocean needs to be mapped in detail because it's one large system. Where I used to 'add up' the contributions myself, there is now a whole team that makes the calculations. With more and more data, we are able to better represent all possible future scenarios and assess the likelihood of these scenarios. We also want to look further ahead than has been done so far, all the way to the year 2300.
What do you hope to have achieved in 5 years?
In 5 years, I hope to have a more detailed understanding of which factors have caused sea level rise in specific areas. Especially for the rise before 1970, we still don’t have a good explanation. It is more than we would expect based on melted ice and ocean warming. So how is that possible? Do the models for the period after that actually hold up? It’s a bit like a whodunnit, and I’m on the hunt for the culprit.
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