Publisher Summary This chapter traces the history of exploration of the Norwegian, Greenland, and Barents Seas. Exploration of the Northeast Passage (sea way) continued in the XVllth century along with land exploration of the Far East. At this time, the northern part of the Pacific was the least investigated, the contour of Asia north of China was unknown, and the existing map of A. Orthelius (1570) was inexact. Discovery of new lands and Russian trade and political interests for the Far East region instigated geographical expeditions. The development of geographical investigations became an important State policy. In 1969, near the coast of Norway, about 63° N, an international expedition allowed to investigate the thermohaline structure of the Norwegian Coastal Current front on several sections with stations 7 km apart. In the beginning of the 70's, the Arctic and Antarctic Research Institute (AARI) organized a long-term scientific program “Polar Experiment” aimed at the study of the large-scale interaction between the ocean and the atmosphere in the Polar areas. The program “POLEX-Sever” intended to—(1) study the interannual changes of the large-scale anticyclonic water circulation in the Arctic Basin and its connection with ice conditions of the marginal seas, (2) study the water exchange between the Arctic Ocean and the adjacent regions of the Atlantic and Pacific Oceans, and (3) study the role of the ice cover in the energy exchange between the ocean and the atmosphere.