Tidal predictions

The National Tidal Centre provides tidal predictions for Australian Antarctic and sub-antarctic stations and Australian ports for any seven days with the start date nominated by you.

Below are the links to the Australian Antarctic Division web pages for tide predictions for an entire year (2003 to 2007). Predictions are calculated by the National Tidal Centre.

Casey, Davis, Macquarie Island, Mawson, Davis, Zhong Shan

Tide gauge data

Sea level measurements recorded by our tide gauges (recorded every five minutes) are available from the National Tidal Centre.

About

Long term averages of tides give a value for mean sea level which is thought to be changing in response to global climate change. A tide gauge is an instrument for measuring and recording the time and height of the sea surface as it changes with the tides.

The Data Centre in conjunction with the National Tidal Centre and the Geodesy Group of Geoscience Australia, is now operating a number of tide gauges in Antarctica and on the subantarctic islands to monitor long term changes in sea level. This project is the core of an Intergovernmental Oceanographic Commission sponsored Sea Level Pilot Project for the Southern Ocean.

Measuring sea level in the Antarctic region is important for a number of reasons:

• Global sea-level change.
• Determining sea level for determining height datums for mapping and charting.
• Tidal predictions for shipping. 
• Study of inter-annual variability of the circum-polar current and links with inter-annual climate variability, such as the El Niño-Southern Oscillation phenomenon.
• The study of tides - particularly cross-shelf transport of heat.
• Calibration of satelite altimeter data.

The earliest Australian tide gauge to be operated in Antarctica was in 1912 when a gauge was installed at Cape Denison, George V Land, for 3 months during the Australasian Antarctic Expedition. This expedition also installed a gauge at Macquarie Island in the mid-Southern Ocean which operated for 9 months. Since then there have been a number of tide gauges in operation in Antarctica and on Heard and Macquarie Islands, but only for short periods.

In 1991 the Antarctic Division, in collaboration with the then National Tidal Facility (Now National Tidal Centre), Flinders University of South Australia and AUSLIG embarked on a program to install tide gauges in Australian Antarctic Territory and the Southern Ocean. The objectives of this program include the determination of mean sea level for mapping and charting and research into long term sea level change. A two-phase approach to tide gauge deployment was adopted to allow immediate deployment while designs for permanent installations were investigated. The first new freestanding, bottom-mounted tide gauge specially designed for Antarctic use and built in Hobart, was deployed at Mawson in February 1992. This was followed by the deployment of tide gauges at Davis and Casey. In August 1993 a tide gauge of a similar type was deployed at Heard Island. In December 1993 a permanent tide gauge was deployed at Macquarie Island by drilling an inclined hole through the rock and installing an Aquatrak acoustic tide gauge. Permanent GPS base stations have been deployed at each permanent Antarctic station and at Macquarie Island to provide geodetic control for the tide gauges.

The bottom mounted tide gauges at Mawson, Davis and Macquarie Island have now been operating successfully for over ten years which is a record for Australian Antarctic tide gauge installations. The Macquarie Island, Casey and Mawson shore mounted tide gauges can be interrogated remotely for data and the functioning of the tide gauge.

Taking measurements from the Davis tide gauge through the sea ice.

Location of gauges

SCAR Geoscience Standing Scientific Group, Permanent Tide Gauge Observatory Sites web pages.

A map of the location of tide gauges

There are also maps showing the details of the locations of each of the gauges:

• Macquarie Island
• Casey
• Davis
• Mawson (see also Mawson station map)
• Zhongshan

Gauge types

Macquarie Island — Shore Mounted Gauges

The system consists of two separate sensors contained in separate housings on a rock shelf on the northern side of Garden Cove. One of the sensors is an Aquatrack acoustic type and the other is a Druck pressure transducer. Both housings contain a Platypus Engineering data logger and a 12V 15 Ah gel type battery. Each housing consists of an Admiralty Bronze ring bolted down to a concrete plinth and a glass fibre reinforced cover held down by a single central bolt and nut. The bolt top is covered by a sealed blind nut.

Both gauges obtain access to the ocean via a hole about 12 metres long inclined at approximately 34 and 39 degrees to the horizontal. Each hole is lined with a plastic pipe which is normally not removable. In the Aquatrack sensor hole a 50mm ABS pressure pipe runs down inside the liner and is fitted with a brass strainer and orifice at the lower end.

The Macquarie Island shore mounted gauge was commissioned in January 1994. 

Antarctica — Shore Mounted Gauge

To study small changes in sea level over a long period of time it is necessary for the datum of the gauge to remain fixed. This is possible but very difficult with the bottom mounted gauges. A design similar to the bore hole Aquatrack installation at Macquarie Island has been modified for Antarctica. To overcome the freezing of the water in the borehole it will be heated and lined with a double metal lining which acts like a thermos flask.

The Mawson shore mounted gauge was commissioned in February 2003. 

The Casey shore mounted gauge was installed in the new wharf and was commissioned in February 2005.

Bottom Mounted Gauges

The bottom mounted gauges used in Antarctica were designed and constructed by Platypus Engineering in Hobart. The overall accuracy of the system is better than +/- 3 mm for a known water density.

The gauges have been deployed in a water depth of about 7 - 8 metres. The gauge measures pressure using a Paroscientific Digiquartz Pressure Transducer with a full scale pressure of 30 psi absolute and a a resolution of 1.4 mm.. The accuracy of the transducer is 1 in 10,000 of full scale over the calibrated temperature. The recorders have a five year battery life and two years data storage. Data are logged on board the tide gauge. Data can be stored for up to two years before the rotating buffer overwrites the oldest data. Data are downloaded from the tide gauge by means of an induction coil lowered from the surface over the top of the tide gauge.

Mawson bottom mounted gauge commissioned in March 1992.

Davis bottom mounted gauge commissioned in April 1993.

Casey bottom mounted gauge commissioned in March 1996.

Larsemann Hills (Nella Fjord) bottom mounted gauge commissioned in February 2000.

Diagram of a bottom mounted tide gauge

The future

Recommendation 7 of the Government's response to the Foresight Report states "In order to allow more flexibility in the use of resources, Australia should develop alternative and fully automated means of conducting current monitoring programs."

We are seeking ways of automating the tide-gauge network. The shore-mounted gauges do not present a problem in communicating tidal information in near real time. As the information is collected, it is able to be transmitted via cable modem and satellite to Kingston and the National Tidal Centre. We are able to deploy shore-mounted gauges in station areas where there is ready access to a steep shoreline, power and water that is deep enough to reduce wave action.

Bottom-mounted gauges must be deployed in areas that are not suitable for shore-mounted gauges. These bottom-mounted gauges are more problematic in the maintenance of effective communications and power linkages. The Antarctic is an extremely difficult environment to deploy bottom-mounted gauges — sea-ice or icebergs can carry off gauges and destroy cabling. Running cables, even in piping is problematic with sea-ice, while digging ditches for cables on rock substrate is extremely costly in this environment.

There is no easy solution to automation in this situation. Research is underway to examine very low frequency communication between the tide gauge and a shore mounted transmitter/receiver.

Sea level change

(Source: Climate Change - The IPCC Scientific Assessment. 1990)

Rate/amount of sea level change:

• 5 cms rise - at best = 1.38 mm/yr
• 40 cms rise - at worst = 11.11 mm/yr until 2030
• 26 cms rise - best estimate = 7.22 mm/yr

Contributions to sea level change:

• Thermal expansion: +52%
• Alpine glaciers and small ice caps: +49%
• Greenland: +12%
• Antarctica: -13%

Total: 100%

Further information - IPCC Executive Suumary

For more information, contact the mapping officer.