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Monthly periodicity in acoustic reflections and vertical motions in the deep ocean
Author(s) -
van Haren Hans
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl029947
Subject(s) - geology , amplitude , internal wave , acoustic doppler current profiler , oceanography , diel vertical migration , climatology , zooplankton , geodesy , atmospheric sciences , current (fluid) , physics , quantum mechanics
A recent, 1.5 years long record of acoustic Doppler current profiler (ADCP)‐data from the Canary Basin (North‐Atlantic ocean) likely reflects vertical zooplankton migration between 800 and 1400 m. This record clearly distinguishes 3 major periodicities of down‐ and upgoing motions to within a precision of ∼1/400: a daily, a seasonal and a monthly cycle. Largest daily excursions occur during full moon. The directly observed hourly mean vertical velocity amplitudes of ∣w∣ = 0.025 ± 0.01 m s −1 are too slow for particles from the observational depths to reach the zone of moon‐ (and only very weak sun‐) light penetration in half a day. It is shown that no physical (internal wave), geochemical or sinking food mechanism can trigger the daily and monthly cycles, which are coupled. It is speculated that an entrained biorhythm running precise internal biochemical clocks controls the vertical migration.