2010),

these two flows have quite different dimensional and non-dimensional dynamic parameters. The Słupsk Furrow gravity current has a larger width W   (25 km vs. 10 km) and thickness H   (34 m vs. 11 m) and a smaller mean downstream interfacial slope Sx′   (1.5 × 10−4 vs. 5.0 × 10−4), bulk buoyancy B   (0.034 m s−2 vs. 0.07 m s−2), friction velocity u* (0.015 m s−1 vs. 0.02 ms−1), bulk flow velocity U   (0.3 m s−1 vs. 0.5 ms−1), Froude number Fr (0.27 vs. 0.54) and Ekman number Ek=(u′*2U−1f−1H−1)2(2.7×10−2vs.≈1). Though Ek ≪ l in the case of Słupsk Furrow, both this website gravity currents can be regarded as frictionally controlled, because the Ekman depth δE = 0.4u*/f exceeds H ( Umlauf & Arneborg 2009a). That is why in both cases the transverse structure of the gravity current is characterized by the presence of a thin interfacial jet directed to the right of the down-channel flow. Note that in the case when the Ekman layer thickness is much smaller than the channelized gravity flow itself, the transverse velocity structure does

not display a thin interfacial jet but a secondary flow field consisting of frictionally induced Ekman transports across the channel in the benthic and interfacial boundary layers and a return flow in the interior ( Cossu et al. 2010). The small value of the Froude number in the Słupsk Furrow gravity current relative to that of the Arkona Basin (Fr = 0.27 vs. Fr = 0.54) implies a reduced amount Megestrol Acetate of entrainment in the former case. To estimate the entrainment of surrounding waters to a gravity 5-FU datasheet current, one can use a new empirical parameterization suggested by Cenedese & Adduce (2010) based on laboratory and field measurements equation(4) E=Min+A Frα1+ACinf(FR+FR0)α,Cinf=1Max+1Reβ,where E = we/U is the entrainment ratio, we is the entrainment velocity, Re = U H/v is the Reynolds number, v ≈ 1.3×10−6 m2 s−1 is the kinematic molecular viscosity of water, and Min = 4 × 10−5, Max = 1, A = 3.4 × 10−3, Fr0 = 0.51, α = 7.18 and β = 0.5 are empirical constants based on the limited oceanographic and laboratory data available. Substituting the above parameters of gravity flows into

equation (4) one obtains E = 4.03 × 10−5 ≈ Min for the simulated gravity flow in the Słupsk Furrow and E = 8.0 × 10−5 for the Arkona Basin gravity current. Therefore, the entrainment in the Słupsk Furrow is twice as small as that of the Arkona Basin. Note that the last estimate (E = 8.0 × 10−5) is close to the observed value E = 6.6 × 10−5 ( Arneborg et al. 2007). The simulation of the same flow using MIKE 3 yielded results almost identical to those of POM (cf. Figures 4 and 6). The only difference worth mentioning is an inverted, hydrostatically unstable salinity/density stratification in BBL simulated with MIKE 3 instead of the vertically uniform stratification simulated with POM. This difference can be interpreted as follows.