Ekman, Vagn Walfrid

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Ekman, Vagn Walfrid

(b. Stockholm, Sweden, 3 May 1874; d. Gosted Stockaryd, sweden, 9 March 1954)

oceanography.

Ekman belonged to the group of Scandinavian oceanographers who, at the beginning of this century, started a new and very fruitful line in physical oceanography. He worked with Fridtjof Nansen, Vilhelm Bjerknes, and B. Helland-Hansen and, like them, must be ranked as one of the great oceanographers.

Ekman was the youngest son of Fredrik Laurentz Ekman, a professor who also worked in oceanography. He went to school in Stockholm and then studied at the University of Uppsala. His interest in hydrophynamics and oceanography came through his contact with Bjerknes, who introduced him to the theoretical problem of the “wind sprial,” which became the subject of his thesis. The original idea of the spiral came from Nansen, who observed a systematic drift of the ice to the right of the wind direction during his famous Frame expedition. Nansen duggested that Ekman investigate the problem mathematically, resoning that each layer of the sea must be set in motion by the layer immediately above and be successively more deflected to the right by the Coriolis force (on the northern hemisphere). Ekman’s thesis was a short paper in Swedish publication in 1902, and it did not immediately attract any attention. through an enlarged paper,“On the Influence of the Earth’s Rotation on Ocean Currents,” published in 1905 in Arkiu för matematic, astronomy och fysik, his theory became known to the international scientific community. Its importance has since been well established. The “Ekman layer” is one of the cornerstones of modern theories of oceanic circulation, and theoretical and experimental works on rotating fluids.

Another important theoretical contribution was given in a paper published in 1923 in the same journal. Here Ekman developed, for the first time, a complete mathematical theory for the wind-driven circulation in an oceanic basin. It took almost thirty years before a new generation of theoretical oceanographers was able to catch up with these ideas and build further on Exman’s theory. Both the 1905 and the 1923 papers are masterpieces of clarity and elegance and can certainly be enjoyed by all those interested on the subject, whether professionally or not. The first paper has been reprinted in booklet form by the Royal Swedish Academy of Sciences, Stock-holm, and there are plans to print an English edition of the second paper.

Ekman was a very good experimentalist. He made determinations of the equation state for seawater and studied several important hydrodynamic phenomena both in the widly known of his studies is that devoted to dead water, the most of his studies is that devoted to dead water, the strong resistance experienced by ships in the Norweigan fjords because of a particular stratification of the water.

Ekman also constructed oceanographic instruments. His current meter, which gives speed and direction by use of a purely mechanical system, is still a standered tool in oceanographic studies. With Helland-Hansen, Ekman made a number of cruises in the Norwegian Sea to test his current meter. Later, in 1930, he cruised to the trade-wind belt in the Atlantic to carry out systematic current measurements. Unfortunately some of the material was lost during World War II, and it was not until 1953, when Ekman was seventy-nine, that the results were finally published. As usual, Ekman had perfected his work in every detail.

While carrying out his oceanographic research, Ekman was assistant at the International Oceanographic Laboratory in Oslo from 1902 to 1908, then lecturer in mechanics and mathematical physics in Lund, where he received a full professorship in 1910. He became a member of several learned societies and received the Agassiz Medal in 1928 and the Vega Medal in 1939. Ekman published a total of more than 100 scientific articles as well as several articles on philosophical and religious subjects. He was an active member of the Lutheran church and published in its newspaper, Krykobröderna.

Ekman was extraordinary in his requirements for truth and exactness in every detail, both in his scientific work and in his private life. He believed that no human being has the right to cause injustice or harm to anyone else, and he certainly lived up to his ideals. Governed rigorously by his principles, Ekman may have appeared impersonal to some, but he had a warmth and spontaneity that was revealed to his family and close friends.

BIBLIOGRAPHY

A complete bibliography, with biography by B. Kullenberg is given in a repr of “On the Influence of the Earth’s Rotation on Ocean Currents” (Uppsala, 1963). Among his works are “On Dead Water,” in The Norwegian North Polar Expedition 1893–1896. Scientific Results, V (1904), 15; “On the Influence of the Earth’s Rotation on Ocean Currents,” in Arkiv för matematik, astronomi och fysik, 2 (1905), 11; Tables for Sea Water Under Pressure, Conseil Permanent International pour l’ Exploration de la Mer, Publication de Circonstance, no. 49 (1910); “Über Horizantalzirkulation bei winderzeugten Meeresstömungen,” in Akiv för matematik, astronomi och fysik, 17 (1923), 26; On a New Repeating Current Meter, Coseil Permanent International pour l’Exploration de la Mer, Publication de Circonstance, no. 91 (1926); and “Turbulent, Periodic and Mean Motions. Some Measurements in the Atlantic,” in Procès-verbaux. Association d’océanographie physique, 4 (1949) written with B. Helland-Hansen.

Pierre Welander

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