Wave-induced Flow over Mururoa Atoll Reef

Abstract

A unique long-term timeseries of current over Mururoa atoll reef is presented here. Comparison with TOPEX/POSElDON satellite altimeter data reveals that the daily-averaged cross-reef current is wave-driven and varies at the synoptic time scale. This current also exhibits variations at or near the tidal frequency. In order to understand this evolution, a previously published analytical model of the wave-induced flow over a reef flat is used (SYMONDS et al., 1995). Forced by the altimeter data and the tide, it gives results which agree well with field data. It appears that the model is able to reproduce the observed long-term variations of the inward current and also its variations at tidal frequency. Furthermore, the model gives an explanation of the observed six-hour period signal. It reveals that the response of the cross-reef current to the tidal forcing highly depends on the reef geometry and particularly on the water depth over the reef flat. This confirms that the response of the current over a reef flat at or near the tidal frequency is site-specific.