DOI: 10.1594/pangaea.701279
title: Continuous VM-ADCP (vessel-mounted acoustic Doppler current profiler) profiles of horizontal velocities and raw acoustic gain control data during Polarstern cruise ANT-XVIII/2

description: The mixing regime of the upper 180 m of a mesoscale eddy in the vicinity of the Antarctic Polar Front at 47° S and 21° E was investigated during the R.V. Polarstern cruise ANT-XVIII/2 within the scope of the iron fertilization experiment EisenEx. On the basis of hydrographic CTD and ADCP profiles we deduced the vertical diffusivity Kz from two different parameterizations. Since these parameterizations bear the character of empirical functions, based on theoretical and idealized assumptions, they were inter alia compared with Cox-number and Thorpe-scale related diffusivities deduced from microstructure measurements, which supplied the first direct insights into turbulence of this ocean region. Values of Kz in the range of 10**-4 - 10**-3 m**2/s appear as a rather robust estimate of vertical diffusivity within the seasonal pycnocline. Values in the mixed layer above are more variable in time and reach 10**-1 m**2/s during periods of strong winds. The results confirm a close agreement between the microstructure-based eddy diffusivities and eddy diffusivities calculated after the parameterization of Pacanowski and Philander [1981, Journal of Physical Oceanography 11, 1443-1451, doi:10.1175/1520-0485(1981)011&lt;1443:POVMIN&gt;2.0.CO;2].
description: This data set was obtained during the R. V. Polarstern cruise ANT-XVIII/2 dedicated to perform the iron fertilization experiment EisenEx. Current velocities were measured continuously along the ship's track with an RD Instruments, vessel-mounted, 153.6-kHz narrow band ADCP. The transducers were located 11 m below the water line and were protected against ice floes by an acoustically transparent plastic window. The current measurements were made using a pulse and vertical bin length of 4 m. The averaging interval was 120 seconds. The reference layer was set to bins 6 to 15 avoiding near surface effects and biases near bin 1. Heading, roll and pitch data from the ship's gyro platforms were used to convert the ADCP velocities into earth coordinates. The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS) or DGPS if available. Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. The ADCP data were processed using the CODAS3 software package (developed by E. Firing and colleagues, SOEST, Hawaii). The raw data of the acoustic gain control for each transducer, which is related to the backscatter strength, were also recorded, but are left uncalibrated and uncorrected for beam spreading and sound absorption.Sampling interval: 120 s; Number of bins: 80; Bin length: 4 m; Pulse length: 4 m; Blank beyond transmit length; 4 m; Top reference bin: 6; Bottom reference bin: 15; Amplitude: 1.0012 ± 0.0144; Phase: 0.6349 ± 0.9362Raw data file stored at doi:10.1594/PANGAEA.744078CODAS software manual at hdl:10013/epic.37616.d001
description: Supplement to: Cisewski, Boris; Strass, Volker H; Prandke, Hartmut (2005): Upper-ocean vertical mixing in the Antarctic Polar Front Zone. Deep Sea Research Part II: Topical Studies in Oceanography, 52(9-10), 1087-1108