Tide gauges that withstand stormy seas and Antarctic ice

We measure tides for many different research and operational purposes. Such measurements have a practical value in determining sea level for mapping elevations and ocean depths, tidal predictions for shipping, and in the calibration of satellite altimeters.

Tide measurements also have a research value. Sea level data helps us understand long-terrm climate change as well as continental readjustment, heat transfer across the continental shelf, and other oceanographic phenomena including observation of the recently-observed Southern Ocean oscillation.

The Antarctic region had no effective tide-measuring network until recently. The Australasian Antarctic Expedition installed tide gauges at Cape Denison and Macquarie Island in 1912. Several gauges have operated in the region since then, but only for short periods.

Antarctic and subantarctic coasts are difficult places for measuring tides. Rough seas and floating Antarctic ice regularly destroy both sea-bottom and shore structures. In 1991 the Australian Antarctic Division, with support from other national research and administrative bodies, made a concerted effort to obtain long-term tide data by installing gauges in Antarctica and the Southern Ocean.

At Macquarie Island, access to the sea was gained via an inclined bore hole, with thegauge and electronics in a sealed fibre glass dome at the top of the hole. In Antarctica, 600-kg concrete moorings containing gauges in areas relatively free of icebergs have operated for eight years at Mawson and Davis and at Casey for five. A new shore gauge at Mawson will use an inclined borehole to the sea, heated to stop the water from freezing.

The tidal data will need to be gathered for another decade or more before any long term sea level trends can be detected.

Henk Brolsma
Mapping Officer,
Australian Antarctic Division

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