Abstract
Abstract. The oceanographic campaign CARPET2014 (Characterizing Adriatic Region Preconditionig EvenTs), (30 January–4 February 2014) collected the very first turbulence data in the Gulf of Trieste (northern Adriatic Sea) under moderate wind (average wind speed 10 m s−1) and heat flux (net negative heat flux ranging from 150 to 400 W m−2). Observations consisted of 38 CTD (Conductivity, Temperature, Depth) casts and 478 microstructure profiles (grouped into 145 ensembles) with three sets of yoyo casts, each lasting for about 12 consecutive hours. Averaging closely repeated casts, such as the ensembles, can lead to a smearing effect when in the presence of a vertical density structure with strong interfaces that can move up or down between subsequent casts under the influence of tides and internal waves. In order to minimize the smearing effect of such displacements on mean quantities, we developed an algorithm to realign successive microstructure profiles to produce sharper and more meaningful mean profiles of measured turbulence parameters. During the campaign, the water column in the gulf evolved from well-mixed to stratified conditions due to Adriatic waters intruding at the bottom along the gulf's south-eastern coast. We show that during the warm and relatively dry winter, the water column in the Gulf of Trieste, even under moderate wind forcing, was not completely mixed due to the influence of bottom waters intruding from the open sea. Inside the gulf, two types of water intrusions were found during yoyo casts: one coming from the northern coast of the Adriatic Sea (i.e. cooler, fresher and more turbid) and one coming from the open sea in front of the Po Delta (i.e. warmer, saltier and less turbid). The two intrusions had different impacts on turbulence kinetic energy dissipation rate profiles. The former, with high turbidity, acted as a barrier to wind-driven turbulence, while the latter, with low sediment concentrations and a smaller vertical density gradient, was not able to suppress downward penetration of turbulence from the surface.
Highlights
Turbulence and associated processes are gaining a broader interest within the ocean sciences community for their fundamental role in many ocean phenomena (Gargett, 1997; Thorpe, 2005)
We show that during the warm and relatively dry winter, the water column in the Gulf of Trieste, even under moderate wind forcing, was not completely mixed due to the influence of bottom waters intruding from the open sea
The Gulf of Trieste (GoT ) is a small and shallow bay located in the north-eastern corner of the Adriatic Sea (Fig. 1). It is generally classified as a region of freshwater influence (ROFI; Simpson et al, 1993) due to intense riverine discharges and undergoes a marked seasonal variability
Summary
Turbulence and associated processes are gaining a broader interest within the ocean sciences community for their fundamental role in many ocean phenomena (Gargett, 1997; Thorpe, 2005). Peters et al (2007) reported a second set, collected in February 2003 within the DOLCEVITA project in the shallow northern Adriatic under strong winds, intense cooling and a well-mixed water column Their main findings highlight different contributions of surface forcing and bottom friction on the TKE dissipation rate profiles. All of the studies cited above deal almost exclusively with the surface mixed layer and only Peters et al (2007) discuss the role of the bottom boundary on turbulent dissipation rates This means that the interaction between surface and bottom turbulence has only been described briefly in the Adriatic Sea. In this study a sub-set of observations will be described, which were collected during the CARPET2014 (Characterizing Adriatic Region Preconditionig EvenTs) campaign onboard the R/V Urania in the northern Adriatic Sea between 29 January and 10 February
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