A new view of near-shore dynamics based on observations from HF Radar

Since 1984 the OSCR HF Radar system has been used in over 50 deployments to measure near-shore surface currents for both scientific and engineering applications. The enhanced scope, resolution and accuracy of these measurements have yielded new insights into the tidal, wind and density driven dynamics of the near-shore zone.Tidal current ellipses obtained from these radar measurements have been shown to be in good aggrement with values calculated by numerical models both for the predominant constituents and also for higher harmonics. Coherent patterns of wind-forced currents ahve been determined with strong evidence of a “slab-like” surface response. In one deployment, with offshore winds blowing over relatively deep water, this “slab” rotated clockwise at near-inertial frequency. Strong (up to 20cm s⁻¹), persistent surface residual currents are commonly observed, these are almost certainly generated by (small) horizontal density gradients. These observed surface residuals provide ideal data for rigorous testing of 3-D numerical models.With a threatened rise in sea level, HF Radar is well-suited for observing the expected changes in the dynamics of near-shore regions. Continuing development of these radar systems offers exciting prospects of remote sensing of both surface waves and currents. Future applications may extend beyond the near-shore region to measurements along the shelf-edge, in oceanic gyres and for “beach-processes”.