gradient at 1 < R ρ < 1.5. The reason for the upper limit ðR ρ < 2Þ follows from the
conclusions of [27] that the finger growth rate depends on the local buoyancy
period and should be shorter than this period, which happens only when R ρ is
smaller than 2. The intensity and speed of their formation increase as R ρ decreases.
Recently, it was found [25], that at R ρ → 1, the behavior of the salt finger system
becomes transient and the growth rate of salt fingers becomes very high.
The criteria for evaluation of the type of the stratification as well as of the fine
structure formation occurring in the stratified water medium are based on the
interrelations of the vertical stability of stratification and the density ratio [3, 9]. We
used these criteria, and added to them, when appropriate, the limiting restrictions on
R ρ for salt fingering development.
1. Complete,
or
absolute,
stability:
ΔT < 0,
ΔS > 0,
E θ, S > 0,
ðE T > 0, E S > 0Þ, R ρ < 0. Stratification is convectively stable. The effects of
double-diffusion convection are excluded.
2. Convectively unstable stratification (in the form of salt fingers): ΔT < 0, ΔS < 0,
E θ, S > 0, ðE T > 0, E S < 0Þ, R ρ > 1.
At R ρ > 1 stratification is convectively unstable due to double diffusion.
At 0 < R ρ < 1 the stratification is hydrostatically unstable.
3. Convectively unstable stratification (in the form of interleaving convection):
ΔT > 0, ΔS > 0,
E θ, S > 0, ðE T < 0, E S > 0Þ, R ρ > 1.
At R ρ > 1 stratification is convectively unstable due to double diffusion.
At 0 < R ρ < 1 the stratification is hydrostatically unstable.
4. Absolute instability: ΔT > 0, ΔS < 0, E θ, S < 0, ðE T < 0, E S < 0Þ, R ρ < 0.
With the use of the limitative restrictions for salt fingering development, the
conditions in the brackets are redundant. With our goal of showing the reality of salt
fingering convection, evaluation of intensity and types of the vertical thermohaline
structure included an assessment of the character of ΔT and ΔS background profiles
and separate intervals, estimates of parameters of stability E θ, S and R ρ and their
relationship. In the vertical interval satisfying the second criteria, the restrictive
conditions for intense development of salt fingers 1 < R ρ < 2 were applied. Such
approach was used for detecting and identifying vertical intervals of favorable
conditions for salt fingering development. Computed profiles of the density ratio
and of the vertical stability together with thermohaline profiles in the pressure field
are considered below.
Vertical Distribution of the Stability Parameters
The stability parameters based on the CTD data were first computed using vertical
averaging of 1, 3, 5, 10, and 20 dbar. It turned out that a step of 3 db provided the
relatively high vertical resolution at satisfactory stability of the profiles. It provides
Thermohaline Structure and Salt Fingering …
439
conclusions of [27] that the finger growth rate depends on the local buoyancy
period and should be shorter than this period, which happens only when R ρ is
smaller than 2. The intensity and speed of their formation increase as R ρ decreases.
Recently, it was found [25], that at R ρ → 1, the behavior of the salt finger system
becomes transient and the growth rate of salt fingers becomes very high.
The criteria for evaluation of the type of the stratification as well as of the fine
structure formation occurring in the stratified water medium are based on the
interrelations of the vertical stability of stratification and the density ratio [3, 9]. We
used these criteria, and added to them, when appropriate, the limiting restrictions on
R ρ for salt fingering development.
1. Complete,
or
absolute,
stability:
ΔT < 0,
ΔS > 0,
E θ, S > 0,
ðE T > 0, E S > 0Þ, R ρ < 0. Stratification is convectively stable. The effects of
double-diffusion convection are excluded.
2. Convectively unstable stratification (in the form of salt fingers): ΔT < 0, ΔS < 0,
E θ, S > 0, ðE T > 0, E S < 0Þ, R ρ > 1.
At R ρ > 1 stratification is convectively unstable due to double diffusion.
At 0 < R ρ < 1 the stratification is hydrostatically unstable.
3. Convectively unstable stratification (in the form of interleaving convection):
ΔT > 0, ΔS > 0,
E θ, S > 0, ðE T < 0, E S > 0Þ, R ρ > 1.
At R ρ > 1 stratification is convectively unstable due to double diffusion.
At 0 < R ρ < 1 the stratification is hydrostatically unstable.
4. Absolute instability: ΔT > 0, ΔS < 0, E θ, S < 0, ðE T < 0, E S < 0Þ, R ρ < 0.
With the use of the limitative restrictions for salt fingering development, the
conditions in the brackets are redundant. With our goal of showing the reality of salt
fingering convection, evaluation of intensity and types of the vertical thermohaline
structure included an assessment of the character of ΔT and ΔS background profiles
and separate intervals, estimates of parameters of stability E θ, S and R ρ and their
relationship. In the vertical interval satisfying the second criteria, the restrictive
conditions for intense development of salt fingers 1 < R ρ < 2 were applied. Such
approach was used for detecting and identifying vertical intervals of favorable
conditions for salt fingering development. Computed profiles of the density ratio
and of the vertical stability together with thermohaline profiles in the pressure field
are considered below.
Vertical Distribution of the Stability Parameters
The stability parameters based on the CTD data were first computed using vertical
averaging of 1, 3, 5, 10, and 20 dbar. It turned out that a step of 3 db provided the
relatively high vertical resolution at satisfactory stability of the profiles. It provides
Thermohaline Structure and Salt Fingering …
439