Tide and current observations in the central Chukchi Sea during the summer of 2012

Current data from a moored Acoustic Doppler Current Profiler (ADCP) deployed at 69°30.155´N, 169°00.654´W in the central Chukchi Sea during 2012 summertime is analyzed in the present paper. Characteristics of tidal and residual currents are obtained with Cosine-Lanczos filter and cross-spectral analyses. The main achievements are as follows: 1) Along with the local inertial frequency of 12.8 h, two other peaks at ~12-h and ~10-d dominate the time series of raw velocity; 2) The M₂ dominates the 6 resolved tide constituents with significant amplitude variations over depth and the ratios of current speed of this constituent to that of the total tidal current are 54% and 47% for u and v components, respectively. All the resolved tidal constituents rotate clockwise at depth with the exception of MM and O₁. The constituents of M₂ and S₂ with the largest major semi-axes are similar in eccentricity and orientation at deeper levels; 3) The maximum of residual currents varies in a range of 20–30 cm s^?1 over depth and the current with lower velocities flow more true north with smaller magnitudes compared to the current in surface layer. The ~10 d fluctuation of residual current is found throughout the water column and attributed to the response of current to the local wind forcing, with an approximate 1.4 d lag-time at the surface level and occurring several hours later in the lower layer; 4) Mean residual currents flow toward the north with the magnitudes smaller than 7 cm s^?1 in a general agreement with previous studies, which suggests a relatively weaker but stable northward flow indeed exists in the central Chukchi Sea.