Articles

Title:	Downwelling-related mesoscale motions at the entrance to the Gulf of Finland: Observations and diagnosis
Authors:	Laanemets Jaan Pavelson Juss Lips Urmas Kononen Kaisa
Abstract:	Hydrographic (towed CTD) and acoustic Doppler current profiler (ADCP) velocity surveys were conducted daily aboard the RV Aranda from July 15 to 26, 1996 at the entrance to the Gulf of Finland, Baltic Sea. Strong alongshore wind forcing that lasted two days caused an intensive downwelling event north of Hiiumaa Island with an approximate 20 m onshore descent of the thermocline. The associated eastward downwelling jet (~30 cm s^-1, width 8-12 km) developed into an anticyclonic eddy with a diameter of ~20 km. A strong jet (~35 cm s^-1, width 4-6 km) was observed in the periphery of the anticyclonic eddy, centered at the depth of reversal in baroclinicity. The geostrophic streamfunctions were derived from ADCP data and combined with the CTD density field to study the variations of isopycnal potential vorticity. The variation of relative vorticity from -0.95f to 1.2f and five-fold changes in the thickness of the selected isopycnal band caused up to fifty-fold variation of isopycnal potential vorticity over the survey area. The distribution of isopycnal potential vorticity as a conservative property correlated well with the isopycnal salinity distribution. The maximum upward and downward velocities, 35 and 26 m d^-1, correspondingly, were estimated through the divergence of the Q-vector using the ω-equation diagnostic technique.
DOI:
Type of paper:	Original research paper
Pages:	15 to 36
Cytation:	Laanemets J., Pavelson J., Lips U., Kononen K., 2005, Downwelling-related mesoscale motions at the entrance to the Gulf of Finland: Observations and diagnosis, Ocean. Hydrob. Studies, 34(2): 15-36
Keywords:	downwelling, jet, anticyclonic eddy, vorticity, vertical velocity, Gulf of Finland
Year:	2005
Category:
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