Seiche

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A standing wave (red) as the sum of two amplifying waves (green and blue) that travel in opposite directions
Differences in the water level in Lake Erie caused by a seiche , recorded between Buffalo  (red) and Toledo (Ohio)  (blue) on November 14, 2003.
Located near the village of Invermoriston on Loch Ness .

As Seiches (French / sɛʃ /) is called standing waves of the water in lakes , bays or docks . They arise when waves approaching the pool are reflected and superimposed on the incoming waves as counter waves. The term Seiche was the end of the 19th century by François-Alphonse Forel from tidal similar drying up of the river banks derived, which he repeated on Lake Geneva was observed. The lakes of the Great Lakes of North America, where up to three meters high fluctuations in the water level are observed.

description

In simple terms, Seiches can be compared to the sloshing of water in a huge bowl. However, standing waves with several wave nodes also occur, as well as complex wave systems (superimposed longitudinally and transversely) corresponding to the different length and width of the lake basin or due to even more complicated basin shapes.

trigger

The periods of the oscillations are between seconds and days ( around one day in the Baltic Sea , three days in Norwegian fjords , seconds in swimming pools ). The driving force in lakes is usually the changing wind effects. The process of increasing the sea ​​level in the coastal area is synonymous in hydrology and meteorology also known as the slosh or bathtub effect.

In marine basins also come earthquakes or tsunamis as a trigger in question. (The extreme effects of the 1946 tsunami in Hilo / Hawaii can be attributed to its amplification by the seiche of Hilo Bay: period of the tsunami 15 minutes, period of the seiche 30 minutes; as a result, every second wave was amplified by the self-movement of Hilo Bay and generated one much greater destruction than any other stretch of coastline of Hawaii.)

Internal seiches

Since water masses of different densities are layered on top of each other in lakes , internal lakes regularly occur, which were only discovered towards the end of the 19th century. The water masses of the different layers move against each other, so that the layers have different thicknesses at one point in time in different areas of the lake and this distribution changes periodically. Such internal wave systems have been extensively researched in Lake Constance , for example .

See also

literature

  • Anton Endrös : Sea fluctuations (Seiches), observed at the Chiemsee , dissertation at the Kgl. Technical University of Munich, Traunstein, 1903
  • Anton Endrös: Die Seiches des Waginger-Tachingersees , session reports of the mathematical-physical class of the KB Academy of Sciences in Munich, Volume XXXV, year 1905, pages 447–476
  • Anton Endrös: The Sims-See and its sea fluctuations (Seiches) , Publisher: Datterer, Freising, 1913
  • Matthias Tomczak , J. Stuart Godfrey: Regional Oceanography . An Introduction. 2nd Edition. Daya, Delhi 2003, ISBN 81-7035-307-6 (English).

Web links

Individual evidence

  1. ↑ G. Rosenhagen: Extreme storm surges on the German coasts. Climate status report 2007 in Deutscher Wetterdienst (DWD.de), accessed on November 18, 2018
  2. ↑ Sylvin H. Müller-Navarra : A forgotten chapter from lake research - Wilhelm Halbfaß (1868-1938), internal Seiches and the Madüsee ( Jezioro Miedwie ). In: Forum Wissenschaftsgeschichte Volume 1, m-press / Martin Meidenbauer Verlagbuchhandlung, Munich 2005, ISBN 978-3-89975-540-4 (also dissertation at the University of Hamburg , 2005).