Danemark et Pays Bas
Prix Balzan 2022 pour glaciation et dynamique de la calotte glaciaire
Discours de remerciement – Rome, 25.11.2022 (vidéo + textes – anglais)
During most of its 4.5 billion years’ history, there were no glaciers on the Earth. At least that is what geological and geomorphological records tell us. We thus live in a very special period, in which glaciers grow and shrink, and, on a time scale of thousands of years, big ice sheets expand and decay over the northern hemisphere continents in a quasi-cyclic way. The thermal balance of our planet is quite delicate: if the Earth-Sun distance would be 5 % smaller, glaciers would never form; if it would be 5 % larger, the Earth would be permanently glacierized. Yet it is the large variation in glacier extent during relatively short periods of time that has a tremendous influence on the surface of the Earth. Related fluctuations in sea level have impacted coastal morphology and ecosystems again and again. Above all, the strong erosive capacity of glaciers, perhaps 10 time stronger than that of running water, has created fjords and lakes in many parts of the world. In fact, 95% of all freshwater lakes on the globe are the result of glacier erosion!
Giving a Balzan Prize to the subject of ‘Glaciation and Ice Sheet Dynamics’ is a great recognition of the importance of this field in Geosciences. Dorthe Dahl-Jensen and me are the lucky ones, and it is clear that we would never have reached the status of Balzan Prize winners without the support of our research teams through the years. We are very grateful for the tremendous honour and recognition, and for the possibilities that the prize money offers to launch new scientific initiatives.
During many years I have studied how glaciers and ice sheet interact with the climate system and the solid earth. I have tried to solve the mystery of the Pleistocene glacial cycles by computer simulation, delivering a few pieces of the puzzle. I found that including the delayed response of the Earth’s crust to ice (un)loading is an essential process. Dealing with the gradual warming at the base of ice sheets, thus allowing faster sliding of the ice, also turned out to be important. However, I felt that computer simulations lacked proper calibration and verification of many processes, and the set-up of meteorological field experiments on glaciers, with all its logistic difficulties, was inevitable. By now, weather stations on glaciers in all corners of the world have delivered invaluable datasets used to verify meteorological models that deal with the exchange of mass and energy at the glacier surface. In recent years, looking at glaciers from space has revolutionized the diagnosis of the present-day ice bodies. This is needed, because global warming forces us to zoom in: the future evolution of glaciers and related sea-level changes is one of the key issues in the climate problem.
What I did not do is looking into the ice sheets. As has become clear in the past decades, the ice sheets of Greenland and Antarctica contain the best archive of climate change and its forcing agents over the past one million years, with a surprisingly high resolution. Ice-core research is a fascinating field, and I better leave it to my co-prize winner Dorthe Dahl-Jensen to elaborate on that.
Ladies and gentlemen, I accept the Balzan Prize with deep gratitude. It is inspiring and makes me feel younger. Thank you!
It is an extreme honor to receive the Balzan Prize together with Hans Oerlemans, my friend, colleague, and collaborator. It is a great recognition of my research – but not mine alone.
To drill and analyze the deep ice cores from Greenland requires a team with a broad span of expertise. Earlier this year we celebrated the centenary of the birth of Willi Dansgaard, who pioneered ice core research in Denmark and in the World. He was my supervisor and mentor, and the ice and climate group in Copenhagen has developed since it was started in the 1960s. In the spirit of Willi, I would like to acknowledge the skills of all in the research group and let you know how proud I am of the excellent researchers and brilliant students here. Without them this would not have been possible.
To look into the ice, to see the layers of snow and ice from years and years ago, has created knowledge on the past climate unmatched by other sources. The deep ice cores from the Greenland ice sheet contain very high-resolution climate records reaching more than 100,000 years back in time. These records show that our climate system has had large and abrupt changes in the past. Such abrupt changes as those seen in the last glacial period are difficult to simulate by the present generation of climate models. The models predicting our future are capable of simulating the climate of the last 150 years by using the observations from the vast net of instrumental records – but would they also be capable of predicting an abrupt change if it were to come during the next 100 years, when the climate will become warmer?
Our results also show that temperatures in Greenland were 5° C warmer during the last interglacial period, the Eemian. During this long warm period of 5,000 years, the Greenland ice sheet lost mass by melting but lost no more than 25% of its volume, corresponding to a global sea level rise of 2 meters. It takes a lot of heat and a long time to melt such a big ice sheet. It is good to know that the ice sheet is so resilient, but it is also predicted that before year 2100 will be warming in the Arctic similar to what we had during the Eemian. We need to take care.
But to shift back to the present time and to my work together with Hans Oerlemans, one of the most wonderful things we have done is to start and develop the Karthaus summer school in the Italian Tyrol, together with Georg Kaser. Here, all the glaciers are disappearing and will probably first appear again only when the climate cools in our distant future. The first PhD programme was held in 1995, and since then more than 500 students have participated. The networks formed and the pride in being a Karthaus student is strong in our research field. To inspire emerging researchers is the most important legacy one can have – and Hans, I think we have done well! I have truly enjoyed the summer schools.
Finally, I would like to thank my colleagues at the Centre for Earth Observation Science at the University of Manitoba. It has been a dream for me to extend my research to look at the impact of the melting ice – the freshwater release into the ocean. The changing ocean conditions impart the living conditions for the people in the communities where fishery is the main source of income. How will their future look and how can research by indigenous and western teams prepare them for the future?
My research would not have been possible without the love and support from my husband Jørgen Peder Steffensen, so the final thanks go to him. It is with great gratitude that I accept the Balzan Prize. Thank you!