Cape Roberts Tide/Meterological Programme

Data from the Tide/Met. installation at Cape Roberts was downloaded on 21-11-93 and again on 30-11-93. The wind speed sensor, which had seized at low speed, and the wind direction sensors, were replaced with refurbished sensors on 21-11-93.

Review of the downloaded data showed that the tide gauge transducer failed on 26-09-93. The transducer resistance was measured and still appears to be connected but may have failed internally or have somehow become frozen. A visual inspection of the transducer head with a underwater video camera showed that the ice foot-pressure ridge extended deeper than usual near the transducer and that a film of submarine ice covered the rock where the transducer head exited. We attempted to unfreeze the transducer with isopropyl alcohol for inspection on 30-11-94 but this had not worked within 24 hours and the attempt was abandoned this season.

If the transducer has failed because of external icing then it should resume measurements by February when the ice melts around Cape Roberts. New data will then continue to be recorded. If the transducer has failed electronically then it should be replaced. This will require active thawing of the transducer which would take 3-5 days in November 1994. We would also plan to refurbish the CR10 data logger at this time to overcome a minor problem with an excitation channel detected this season.

The failure of the tide gauge transducer in 1993 should not detract from the overall success of this programme which has continuously collected 1041 days of hourly tidal data since 20 November 1990 from continental Antarctica. The design of the installation will permit accurate replacement of the transducer without extensive recalibration and only a 26 hour survey calibration.