Harald Ulrik Sverdrup was a truly outstanding Norwegian scientist. His family background and education were strongly conditioned by contemporary Scandinavian culture, history and personalities. His scientific activities ranged from glaciology and magnetism of the Earth to meteorology and oceanography. This book places some of his most important contributions to geophysical science within the context of his own biographical background: His doctoral dissertation "The North Atlantic Trade Wind" was the first study ever to give a consistent picture of the structure, dynamics and thermodynamics of the Earth's trade-wind zones. In "Dynamics of Tides on the North-Siberian Shelf", Sverdrup followed up his careful observations of tides and tidal currents with a thorough theoretical analysis, all done during his years in the Arctic on the Maud. This led to an entirely new concept of the tides in the Arctic Ocean. In "The oceans: Their Physics, Chemistry and General Biology", Sverdrup contributed a comprehensive account of the water masses and currents of the oceans. This was the first attempt at a unified view of the oceans. From 1942 onwards, a series of studies - with his associate W. H. Munk - of the link between wind and waves laid the foundation of methods of forecasting wind waves and swell. This was essential work for the successful landings of troops and equipment during invasions and stimulated a renewed interest in the study of ocean surface waves. "Wind-driven Currents in a Baroclinic Ocean, with Application to Equatorial Currents of the Eastern Pacific Ocean", was one of the first quantitative studies of the link between the prevailing trade winds and associated equatorial currents, and also explained the stability and location of the Equatorial Counter-current.