ADCP measurements from the ICESHELF 94 experiment

Abstract

The ICESHELF 94 Experiment was conducted during April of 1994 from an ice camp in the Lincoln Sea at approximately 84 degrees N, 63 degrees W. An Acoustic Doppler Current Profiler (ADCP) was operated at the camp from 8 to 24 April. This report describes the ADCP configuration and presents the raw data recorded by the ADCP. Processing steps involved in computing horizontal velocities in geographic coordinates from the raw data are described, and time series and spectra of the resulting data are presented. Horizontal velocities with precision of about 1 cm/s were obtained between 27.7 m and 137.0 m depth with 7.8 m resolution. Data were obtained at five minute intervals, but averaged to 1 hr during processing to suppress instrument noise. Spectra show the velocity field to be dominated by variance at semi-siurnal frequency, with a maximum in energy between 50 and 110m depth. Maximum amplitudes of 8 to 10 cm/s were seen near 80 m depth. Velocities from an InterOcean S4 current meter deployed at the same site were compared to those from the ADCP. The largest differences were associated with peaks in the semi-diurnal oscilations, with the S4 underspeeding relative to the ADCP.