Walter W. Immerzeel

Utrecht University, The Netherlands

2018 James B. Macelwane Medal Winner

Steven J. Davis, Walter Immerzeel, Isaac Santos, Drew Turner, and Caroline C. Ummenhofer were awarded the 2018 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony on 12 December 2018 in Washington, D. C. The medal is for “significant contributions to the geophysical sciences by an outstanding early career scientist.”


Since obtaining his Ph.D. in 2008, Walter Immerzeel has established himself as an influential scientist in the field of mountain hydrology and glaciology. He focuses his research on the impact of global warming on snow and glaciers in High Mountain Asia (HMA) and how it affects future water resources in the downstream, densely populated areas. His unique interdisciplinary research line combines innovative fieldwork techniques, remote sensing, and mesoscale meteorological modeling to elucidate glaciohydrological processes at the catchment scale. His most influential study to date (Science, 2010) uses the above techniques to show that contrary to what was previously believed, the contribution of HMA glacial melt to downstream runoff in most Southeast Asian rivers is smaller than a few percent, the exception being the Indus, for which up to 60% of the downstream discharge has its origin in HMA snow and glacial melt. This process understanding is used to predict the effects of climate change on the glaciohydrology and water resources of HMA as a whole. Walter and his group showed that for realistic climate scenarios maximal glacial melt is expected around 2050 in the western HMA, after which increased rainfall will compensate for the decreased meltwater runoff. In a 2017 study in Nature Walter’s group predicted that HMA glaciers could lose up to 65% of their mass by 2100.

The research of Walter and his group has been highly visible among his colleagues and in the international press. For instance, they were the first to use unmanned airborne vehicles (UAVs, or drones) in HMA glacier research, showing that locally, debris-covered glacier melt rates can even be larger than those of debris-free glaciers as a result of lakes and exposed ice cliffs. To draw attention to the detrimental changes that await the region under climate change and how scientific research can help to mitigate these changes, he has used part of his research funds to make brief, insightful documentaries. During his years working in the region, Walter has built up a strong relation with the local Nepali people and scientists. During his Ph.D. track he was employed by the International Centre for Integrated Mountain Development (ICIMOD) and lived in Kathmandu for 2 years. Currently, he still is a guest researcher at ICIMOD. Right after the April 2015 Nepal earthquake Walter joined forces with people in his remote sensing network to provide the Nepali authorities, through his link with ICIMOD, with inventories of earthquake-induced landslides as seen from space.

—Michiel R. van den Broeke, Utrecht University, Netherlands


Dear Michiel, many thanks for this wonderful citation, and I look forward to link the three poles together by working with you. I am also very grateful to AGU, the Macelwane Medal Committee, and esteemed colleagues for the nomination letters.

As someone from the Netherlands, where the highest point is 322.4 meters above sea level, it may seem strange to be awarded the Macelwane Medal on research in high-mountain Asia, and an explanation is justified. After trekking for 3 months through Nepal with my wife, Hilde, during our honeymoon in 1999, the mountains and its people were permanently imprinted in my system. This resulted in a job at the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, where I lived and worked for 2 years. I met Dr. Roberto Quiroz there, who inspired me to pursue a Ph.D. in this field, and it turned out to be a life changer.

I am still working closely with ICIMOD with a unique group of mountain-loving people who dedicated their careers to the understanding and protection of this beautiful region. I specifically mention David Molden, Arun Shrestha, Anna Sinasalo, and Inka Koch. Without your support, many of the scientific achievements would not have been possible. The joined expeditions in the Himalayas have also sparked new friendships and long-lasting international collaborations. Working with incredible scientists, such as Joseph Shea, Patrick Wagnon, and Francesca Pellicciotti, has been a great inspiration and motivation and a lot of fun.

At Utrecht University in the Netherlands, I feel privileged to work with a great group of people. A special thanks to Marc Bierkens, who has been my mentor for years. Our brainstorm sessions formed the basis for many successful papers and proposals, and I hope we can continue like this for years! This medal is not the result of only my work, but it was true team work, and big thanks to Arthur, Emmy, Jakob, Maxime, Philip, Pleun, Remco, Sonu, and René. I also thank my family; my friends; and my wife, Hilde, in particular for making sure I realize what is really important in life and for making me realize what the red thread in my research really is.

There are huge scientific and societal challenges ahead associated with mountains and the millions of people that depend on their resources. I am proud and looking forward to keep working on them.

—Walter Immerzeel, Department of Physical Geography, Utrecht University, Netherlands