The 2003 Hans Oeschger Medal is awarded to Sigfus Johnsen for his outstanding contributions to ice core research through the modeling of water isotopes and their use for paleoclimate reconstruction.
Sigfus Johnsen has been a key player in ice core research since more than 30 years. A physicist born in Iceland he has joined the Niels Bohr Institute of Copenhagen in the late sixties and then shared his research activities between Rejkavik University and the Copenhagen team led by Willi Dansgaard and now by Dorthe Dahl-Jensen. He has been involved in numerous deep drilling programmes in Greenland (Camp Century, Dye 3, Renland, GRIP and North GRIP) and Antarctica (Byrd and now EPICA). His personal contribution to these programmes encompasses a very large spectrum of topics from a direct involvement in deep drilling activities to the more theoretical aspects of the interpretation of ice core data. He is certainly one of the best specialists of water isotopes in ice cores with numerous contributions dealing with isotope atmospheric modeling and climate reconstruction from isotope series, with isotope diffusion in ice and with the combined use of deuterium and oxygen 18 measurements through the deuterium-excess parameters. He is also deeply involved in ice-sheet modeling with specific developments in areas such as ice core dating and temperature reconstruction based on paleothermometry. Sigfus Johnsen is very open to other communities, and he has had very fruitful interactions with paleoceanographers, continentalists and climate modelers.