Gerold Siedler is a physical oceanographer at the marine research institute in Kiel/Germany. He established a highly regarded ocean observing unit and participated in almost 30 research cruises. His research focused on ocean processes and circulation in all three oceans. He was professor at Kiel University, Director of the marine research institute IfM (1976-1978) and Dean of the Faculty of Mathematics and Sciences (1991-1992) at Kiel University. In addition he worked as visiting investigator abroad, in particular at the Woods Hole Oceanographic Institution in the USA, including teaching in the WHOI/MIT joint program. He performed research at the University of Miami, the Jet Propulsion… Laboratory/Pasadena, the University of Hawaii in the USA, the Laboratory for the Physics of the Ocean, Paris and Ifremer/Brest in France, and as a Humboldt researcher at the University of Cape Town in South Africa. He served in leading functions in major international ocean/climate programs, in particular GATE and WOCE. He was a vice-president of the Association for the Physical Sciences of the Ocean (IAPSO, 1975-1979) and a president of the Scientific Committee on Oceanic Research (SCOR, 1983-1988) at ICSU. He published 77 peer-reviewed papers, authored or edited 4 books and contributed to 18 books. He is now Emeritus Professor at Kiel University.