The Rossby whistle is the oscillation of sea-level and bottom pressure in the Caribbean Sea with the period of 120 days and influenced by propagating westward oceanic Rossby wave. It is observed that a baroclinic

Rossby wave Rossby waves, also known as planetary waves, are a type of inertial wave naturally occurring in rotating fluids. They were first identified by Sweden-born American meteorologist Carl-Gustaf Arvid Rossby. They are observed in the atmospheres an ...

propagating westward across the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

, oscillating with a

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

of 120 days, is rapidly returned to the east along the southern boundary as coastal shelf waves. The porous boundary of the Caribbean Sea results in this oscillation influencing a mass exchange with the wider ocean, leading to an almost uniform bottom pressure variability over the Grenada, Venezuela, and Colombia basins. These observations are based on satellite observation of the sea-level, monthly means of basin-averaged ocean bottom pressure using GRACE data,

tide gauge A tide gauge is a device for measuring the change in sea level relative to a vertical datum. It its also known as mareograph, marigraph, sea-level recorder and limnimeter. When applied to freshwater continental water bodies, the instrument ma ...

measurements, and data from a bottom pressure recorder. The oscillation was first found in a

numerical modelling Computer simulation is the process of mathematical modelling, performed on a computer, which is designed to predict the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be dete ...

simulation, from which is shown one cycle of the least squares fit of (left) sea level and (right) bottom pressure on basin averaged bottom pressure in the Caribbean Sea.One cycle of (left) sea level and (right) bottom pressure in the Caribbean Sea. https://www.youtube.com/v/gj9pB0rI08w?playlist=,&autoplay=1&loop=1

Analogy to a whistle

Many atmospheric and oceanic phenomena are periodic (for example

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and ...

s) and the Caribbean Sea is one such example. However, there is an interesting analogy to the operation of a

whistle A whistle is an instrument which produces sound from a stream of gas, most commonly air. It may be mouth-operated, or powered by air pressure, steam, or other means. Whistles vary in size from a small slide whistle or nose flute type to a lar ...

in the way water flows into the semi-enclosed Caribbean Sea, flows out of it, and interacts within that basin. The net inflow and outflow required to explain the basin-averaged pressure signal is only a tiny fraction (about 1/1000) of the observed changes in flows through individual straits. This means that the bottom pressure signal is a side effect of the oscillating mode operating in a basin which can exchange mass with the wider ocean. This is analogous to the operation of a whistle or similar musical instrument. An organ pipe is a system in which the instability of a jet of air on encountering an obstacle generates eddies, and those eddies interact with the natural acoustic modes of the organ pipe.Jeans, J. (1937), Science and Music, Cambridge Univ. Press, New York. That resonance results in an audible sound in a whistle only because it is open. Such analogy was also invoked by LaCasce who compared Rossby wave resonant behavior with ''acoustic waves in a clarinet''. However, there is no audible sound emitted from the Caribbean Sea and it is also not heard from satellites missions such as

Gravity Recovery and Climate Experiment The Gravity Recovery and Climate Experiment (GRACE) was a joint mission of NASA and the German Aerospace Center (DLR). Twin satellites took detailed measurements of Earth's gravity field anomalies from its launch in March 2002 to the end of its ...

which observes Earth's gravity field anomalies.

References

{{DEFAULTSORT:Rossby whistle Physical oceanography