Denmark and The Netherlands

Dorthe Dahl-Jensen and Johannes (Hans) Oerlemans

2022 Balzan Prize for Glaciation and Ice Sheet Dynamics

For their joint and complementary fundamental and groundbreaking contributions to the dynamics of glaciation and ice sheets and their impact on understanding climate change and its mechanisms, paving the way to more reliable projections of ice sheet behavior and related changes in sea level.

During most of its history, the Earth was free of ice. However, there have been numerous episodes with glaciers and ice sheets interacting with the landscape and layers below. Because of the enormous erosive capacity of glaciers, these episodes have been very important in shaping the face of the Earth and its landscapes. The growth and decay of ice sheets are critically dependent on the exchange of mass at the interfaces of atmosphere, ocean, and solid Earth. Therefore, an integrated approach, including quantitative modeling, meteorology, and glaciology, as well as unraveling climate change through ice core research and field campaigns are needed.

Dorthe Dahl-Jensen and Hans Oerlemans have explored these complex issues to better understand the past and predict the future. Together, they have advanced the societal impact of the findings of their pioneering research. As active scientists, both are role models in their field, jointly mentoring a new generation of researchers.

Dorthe Dahl-Jensen has carried out groundbreaking research in polar glaciology and ice core research. Her discoveries have helped to reconstruct the climate of the past by using ice core data applied in a sophisticated, interdisciplinary manner. In 1997 she became the leader of the international NEEM deep ice core project, which for the first time obtained data older than the last glacial maximum. Success in reaching the basal ice generated thousands of years ago at a depth of 2000 meters was revolutionary.

Through outstanding leadership, she succeeded in this major challenge based on her combination of scientific, technical, managerial, and human skills. Additionally, she has developed and advanced novel interpretations of ice cores (including physical properties and flow of ice and melt water at great depths) in relation to climatic conditions in the past. She has demonstrated that temperatures in the past century were higher than the preceding two millennia. In doing so, she has opened a window onto the past that will help us predict the fate of the Earth. Because of her accomplishments, ice core science now forms one of the mainstays for understanding the climate system. Her research findings are vital to quantify how natural and anthropogenic phenomena influence our climate state. She has contributed to all highly cited and trendsetting papers on this topic, playing a central role in climate reconstructions of the northern hemisphere extending back from today to the last interglacial period and transforming our knowledge of climate change.

Her broad outreach to the public and decision makers on urgent questions currently facing humanity make her an inspiring example for young researchers in her field. Her key role in the organization of the very successful Karthaus summer courses is another demonstration of dedicated community service.

Hans Oerlemans has made exceptional contributions to the understanding of the physical processes that connect glaciers and the climate. His work is highly original, of outstanding quality, and of lasting significance. As early as 1980, he performed the first successful simulation of the 100ky glacial cycle in a dynamics ice sheet model with delayed bed response. Two years later, he proposed the first self-consistent numerical model of the Antarctic ice sheet, including bed response, dynamic ice sheet shelves, and a mass-balance field related to topography and climatic state. Hans Oerlemans was the driving force of bringing glaciology and meteorology together by initiating field campaigns in the Alps, Greenland, Iceland, Norway, Svalbard, and Antarctica. Crucial for his highly innovative approach was the integration of in situ measurements, remote sensing, and computer simulations, which yielded new quantitative descriptions of energy balance and glacier mass balance.

Hans Oerlemans was also the first to attempt to separate the deep ocean temperature and ice volume signals in the isotopic record stored in sedimentary cores by means of an ice dynamics model. He introduced a new class of glacier models without relying on large numerical models to study dynamic processes and coupling with climate. Thus, he has pioneered glacier dynamics and ice sheet research by consistently opening new avenues well in advance of later contributors to the field. He guides young researchers and has been actively involved in the organization of the Karthaus Summer School on Ice Sheets and Glaciers in the Climate System. Ongoing research projects include the use of stupas for irrigation in cold regions, the modelling of ice growth on the Lake of St. Moritz, and understanding the tidewater glaciers of Svalbard. He has also served as lead author on three IPCC Climate Assessments (Sea Level Change, Observations, and Modeling), and recently founded the GlaciersAlive Association to foster projects for protecting glaciers.