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The diurnal salinity cycle in the tropics
Author(s) -
Drushka Kyla,
Gille Sarah T.,
Sprintall Janet
Publication year - 2014
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2014jc009924
Subject(s) - salinity , diurnal cycle , stratification (seeds) , environmental science , climatology , diurnal temperature variation , entrainment (biomusicology) , precipitation , bay , outflow , forcing (mathematics) , atmospheric sciences , oceanography , geology , geography , meteorology , biology , seed dormancy , philosophy , botany , germination , dormancy , rhythm , aesthetics
Abstract Observations from 35 tropical moorings are used to characterize the diurnal cycle in salinity at 1 m depth. The amplitude of diurnal salinity anomalies is up to 0.01 psu and more typically ∼0.005 psu. Diurnal variations in precipitation and vertical entrainment appear to be the dominant drivers of diurnal salinity variability, with evaporation also contributing. Areas where these processes are strong are expected to have relatively strong salinity cycles: the eastern Atlantic and Pacific equatorial regions, the southwestern Bay of Bengal, the Amazon outflow region, and the Indo‐Pacific warm pool. We hypothesize that salinity anomalies resulting from precipitation and evaporation are initially trapped very near the surface and may not be observed at the 1 m instrument depths until they are mixed downward. As a result, the pattern of diurnal salinity variations is not only dependent on the strength of the forcing terms, but also on the phasing of winds and convective overturning. A comparison of mixed‐layer depth computed with hourly and with daily averaged salinity reveals that diurnal salinity variability can have a significant effect on upper ocean stratification, suggesting that representing diurnal salinity variability could potentially improve air‐sea interaction in climate models. Comparisons between salinity observations from moorings and from the Aquarius satellite (level 2 version 3.0 data) reveal that the typical difference between ascending‐node and descending‐node Aquarius salinity is an order of magnitude greater than the observed diurnal salinity anomalies at 1 m depth.