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 ...

• Main Authors: Cisewski, Boris, Strass, Volker H, Prandke, Hartmut
• Format: Dataset
• Language: English
• Published: PANGAEA 2005
• Subjects: DATE/TIME; LATITUDE; LONGITUDE; DEPTH, water; Current velocity, east-west; Current velocity, north-south; Acoustic gain control 1; Acoustic gain control 2; Acoustic gain control 3; Acoustic gain control 4; Underway cruise track measurements; Acoustic Doppler Current Profiling, vessel-mounted VM-ADCP; ANT-XVIII/2; Polarstern; European Iron Enrichment Experiment in the Southern Ocean EisenEx; Physical Oceanography @ AWI AWI_PhyOce; Antarc*; Antarctic; Southern Ocean
• Online Access: https://dx.doi.org/10.1594/pangaea.701279; https://doi.pangaea.de/10.1594/PANGAEA.701279

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 ... : 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 ...