Sea level
What is happening to sea levels?
Sea levels around Australia are naturally variable, although records indicate that global sea level has been rising at an increasing rate over the past 130 years.
The largest source of sea level rise is expansion of the oceans as they warm under enhanced greenhouse conditions. Sea level may also be affected by:
- thermal expansion of oceans from increasing temperatures (long term change)
- the melting of glaciers and ice sheets
- variability due to natural cycles over seasonal, inter-annual and decadal time scales (e.g. El Niño events)
- regional differences in weather patterns and ocean currents
- coastal subsidence or uplift.
Sea level around Australia is measured by a network of coastal and island tide gauges. Australia's oldest sea level records, from Port Arthur, Fremantle and Sydney, confirm rising sea level around Australia.
Sea level monitoring station
at Portland, Victoria
Observed sea level trends
- Over the past 50 years, global-average sea level has risen 1 to 2 mm per year.
- In the first half of the 19th century, global sea level was about 200 mm below present levels
- For the period 1915-1998 relative sea level has risen 0.86±0.12 mm per year at Fremantle.
- Between 1897 and 1998 relative sea level has risen 1.38±0.18 mm per year at Sydney.
- Since 1890 sea level is estimated to have risen 1.2±0.2 mm per year at Port Arthur.
Research activities
Australian Baseline Sea Level Monitoring Project
The National Tidal Centre provides the management and operational support to this project, with funding from the Australian Government's Climate Change Science Programme. The project is designed to monitor sea level around the coastline of Australia. The ultimate goal is to identify long period sea level changes, with particular emphasis on the enhanced greenhouse effect on sea level.
www.bom.gov.au/oceanography/projects/abslmp/abslmp.shtml
National Tidal Centre
The National Tidal Centre specialises in sea level monitoring and analysis for the purpose of deriving trends in absolute sea level and producing national tide predictions, tide streams and related information.
www.bom.gov.au/oceanography/projects/ntc/ntc.shtml
Reports
- Climate change and Australia's coastal communities
www.cmar.csiro.au/e-print/open/CoastalBroch2002.pdf
