- In full:
- Vagn Walfrid Ekman
- Born:
- May 3, 1874, Stockholm, Sweden
- Died:
- March 9, 1954, Gostad, near Stockaryd (aged 79)
- Inventions:
- Ekman current meter
- Ekman reversing water bottle
V. Walfrid Ekman
-
Who was V. Walfrid Ekman?
V. Walfrid Ekman (1874–1954) was a Swedish physical oceanographer celebrated for his studies of ocean current dynamics. The terms Ekman layer, Ekman spiral, and Ekman transport are derived from his research.
While still a student, Ekman investigated why drift ice didn't align with the wind direction during the Norwegian North Polar Expedition. His 1902 report considered the balance between wind and sea surface friction, water layers, and the Coriolis force caused by Earth's rotation.
From 1910 to 1939, Ekman was a professor at the University of Lund, Sweden, where he focused on the dynamics of ocean currents. He studied wind-driven ocean currents, also exploring the effects of coasts and bottom topography, and the dynamics of the Gulf Stream.
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What field of science did V. Walfrid Ekman work in?
V. Walfrid Ekman was a Swedish physical oceanographer known for his studies of ocean currents. His research led to the common oceanographic terms Ekman layer, Ekman spiral, and Ekman transport.
While a student at Uppsala, Ekman studied the deviation of drift ice from wind direction, taking into account friction and the Coriolis force. He also invented the Ekman current meter and the Ekman reversing water bottle and derived a formula for seawater compressibility. From 1910 to 1939, he was a professor at the University of Lund, focusing on the dynamics of ocean currents, including wind-driven currents and the Gulf Stream.
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What is the Ekman spiral?
The Ekman spiral is the theoretical effect of the Coriolis effect on current direction, assuming a steady wind over an ocean of infinite depth and uniform viscosity. Swedish oceanographer V. Walfrid Ekman proposed that surface layers move 45° to the right of the wind direction in the Northern Hemisphere and 45° to the left in the Southern Hemisphere.
Successively deeper layers are further displaced, and at a certain depth, water motion opposes the wind direction. Current velocity decreases with depth due to momentum loss during motion transference from layer to layer.
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How did Ekman's research help us understand ocean currents?
V. Walfrid Ekman's research significantly advanced the understanding of ocean currents. After observing that drift ice moved at an angle to the wind direction, Ekman developed a theoretical model in 1902 that explained this phenomenon by balancing the friction between wind and the sea surface with the Coriolis force, which is the Earth’s rotation's deflection force.
His model led to the discovery of the Ekman layer, the Ekman spiral, and Ekman transport, concepts describing the movement of water at different depths and angles relative to wind direction. Ekman's work also explains upwelling and downwelling, which are vertical movements of ocean water that affect nutrient distribution and marine life.
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What is the Ekman transport, and why is it important?
Ekman transport, named after Swedish oceanographer V. Walfrid Ekman, is a phenomenon describing the movement of water in the ocean due to wind. Ekman deduced the existence of this layer in 1902.
The average movement of water particles within the Ekman layer is at a 90° angle to the wind direction: to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. As wind varies across different locations, so does Ekman transport, resulting in convergence and divergence zones in surface waters. Convergence causes downwelling, where surface water is forced downward, while divergence leads to upwelling, where water from below rises to the surface. Upwelling and downwelling occur where wind flows parallel to a coastline.
Upwelling cools surface water, bringing nutrient-rich subsurface water into sunlit areas, creating biologically productive regions. The principal upwelling regions are along the eastern boundary of subtropical ocean waters, such as the coasts of Peru and northwestern Africa.
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How do Ekman’s discoveries impact today’s study of climate and marine science?
V. Walfrid Ekman's studies of ocean currents significantly impact climate and marine science today. His concept of the Ekman layer, the vertical region of the ocean affected by wind-driven surface waters, explains how wind stress, the Coriolis force, and friction balance each other to influence water movement.
Ekman transport, a phenomenon where average water particles within the Ekman layer move at an angle to the wind, leads to upwelling and downwelling. Upwelling brings nutrient-rich subsurface water to the surface, boosting biological productivity, while downwelling forces surface water downward. These vertical movements, though small, extend wind-driven effects into deeper waters, impacting nutrient distribution and marine life.
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V. Walfrid Ekman (born May 3, 1874, Stockholm, Sweden—died March 9, 1954, Gostad, near Stockaryd) was a Swedish physical oceanographer best known for his studies of the dynamics of ocean currents. The common oceanographic terms Ekman layer, denoting certain oceanic or atmospheric layers occurring at various interfaces; Ekman spiral, used in connection with vertical oceanic velocity; and Ekman transport, denoting wind-driven currents, derive from his research.
Ekman was the youngest son of Fredrik Laurentz Ekman, a Swedish physical oceanographer. After finishing secondary school in Stockholm, Ekman studied at the University of Uppsala, where he majored in physics. But lectures on hydrodynamics in 1897 by Vilhelm Bjerknes, one of the founders of meteorology and oceanography, definitely decided the direction of Ekman’s work.
While still a student at Uppsala, Ekman made important contributions to oceanography. When it was observed, during the Norwegian North Polar Expedition, that drift ice did not follow the wind direction but deviated by 20° to 40°, Bjerknes chose Ekman to make a theoretical study of the problem. In his report, published in 1902, Ekman took into account the balance of the frictions between the wind and sea surface, within layers of water, and the deflecting force due to the Earth’s rotation (Coriolis force).
After taking his degree at Uppsala in 1902, he joined the staff of the International Laboratory for Oceanographic Research in Oslo, where he remained until 1909. During those years he proved to be a skilled inventor and experimentalist. The Ekman current meter, an instrument with a simple and reliable mechanism, has been used, with subsequent improvements, to the present, while the Ekman reversing water bottle is used in freshwater lakes and sometimes in the ocean to obtain water samples at different depths with a simultaneous measurement of water temperatures. He displayed his theoretical and experimental talents in his study of so-called dead water, which causes slow-moving boats to become stuck because of a thin layer of nearly fresh water spreading over the sea from melting ice. This phenomenon, frequently occurring in fjords, seriously impeded the Norwegian explorer Fridtjof Nansen in Arctic waters. Ekman demonstrated by experiments in a wave tank that the resistance to the motion of the vessels is increased by the waves that are formed at the interface between layers of water of different densities.
He also derived an empirical formula for the mean compressibility (compression ratio divided by pressure) of seawater as a function of pressure and temperature. This formula is still in use today to determine density of deep seawater which is compressed by hydrostatic pressure.
From 1910 to 1939, Ekman was professor of mechanics and mathematical physics at the University of Lund in Sweden, where he pursued his main interest, the dynamics of ocean currents. He published theories on wind-driven ocean currents, including the effects of coasts and bottom topography, and on the dynamics of the Gulf Stream. He also tried, with partial success, to solve the complex problem of ocean turbulence.
In 1925 Ekman participated in a cruise of a German research ship to the Canary Islands. On finding that data on currents obtained for several days at several marine stations between the Bay of Biscay and the Canary Islands were not sufficient to obtain an average figure, he and a colleague, during the years 1922–29, improved the technique for measuring currents for a prolonged period by collecting data from an anchored ship. After several preparatory cruises for that purpose off the Norwegian coast aboard a Norwegian research vessel, they made a cruise to the trade-wind region off northwestern Africa in the summer of 1930 to determine the average current at various ocean depths at stations occupied for two weeks or longer. Preliminary reports were published soon after the cruise, but Ekman wrote the final report in 1953 at the age of 79. The long delay in publication, partly owing to the loss of important data during the German occupation of Norway, also indicates the unparalleled care he took with his work.
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Although his name and achievements were well known among oceanographers, he rarely attended international meetings—but his genuine kindliness prevented him from becoming a recluse. Most of his teachers and friends, such as Nansen and Bjerknes, were Norwegian; he spent many vacations in Bergen. He sang a beautiful bass, spent much time at the piano, and occasionally composed music. In the fall of 1953, he began a study of turbid currents, which he continued until a few days before his death.