Publication Date:
2022-02-11
Description:
Thermohaline staircases are a well-known peculiar feature of the Tyrrhenian Sea.
Generated by extensive double diffusion processes fueled by lateral intrusions, they
are considered to be the most stable of all the staircases that have been detected in
the world ocean, seeing their persistence of more than 40 years in the literature. Double
diffusion leads to efficient vertical mixing, potentially playing a significant role in guiding
the diapycnal mixing. The present study investigates this process of mixing in the case
of the Tyrrhenian staircases by calculating the heat and salt fluxes in their gradient zones
(interfaces) and the resulting net fluxes in adjacent layers using hydrological profiles
collected from 2003 to 2016 at a station in the heart of the basin interior. The staircases
favor downward fluxes of heat and salt, and the results of the calculations show that
these are greater where temperature and salinity gradients are also high. This condition
is more frequently encountered at thin and sharp interfaces, which sometimes appear
as substructures of the thicker interfaces of the staircases. These substructures are
hot spots where vertical fluxes are further accentuated. Due to the increasing salt and
heat content of the Levantine Intermediate Water (LIW) during the observation period,
a rise in the values of the fluxes was noted in the portion of the water column below
it down to about 1800 m. The data furthermore show that internal gravity waves can
modulate the structure of the staircases and very likely contribute to the mixing, too, but
the sampling frequency of the time series is too large to permit a proper assessment of
these processes. It is shown that, at least during the period of observation, the fluxes
due to salt fingers do not reach the bottom layer but remain within the staircases.
Description:
Published
Description:
672437
Description:
4A. Oceanografia e clima
Description:
JCR Journal
Keywords:
Tyrrhenian Sea
;
thermohaline staircases
;
salt fingers
;
diapycnal mixing
;
heat and salt fluxes
;
03.03. Physical
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
