Following recent commentary on the draft council regulations on coastal inundation, it may be useful to review the situation regarding sea level movements.
Around our coastline, the most obvious effect is the inland migration of the mangrove belt, shown in the picture on the north shore of Phillip Island.
While this widespread phenomenon cannot definitely be attributed to sea level rise, it would certainly be the expected response to the global rise which has been about 15cm over the past 100 years.
In the 20 years from 1993 to 2013 the average rate of sea level rise increased to 3.16mm per year.
Of this, about 2mm per year was due to thermal expansion of the oceans, as the ocean water warmed.
Nearly 1mm per year has been from groundwater extraction, and the remaining small proportion was from melting of continental and glacial ice.
What now? Given increasing CO2 levels, atmospheric and therefore oceanic warming is likely to continue.
Other factors including solar fluctuations, volcanic dust and aerosol pollutants also play a role.
How high? Predictions of sea level rise this century range from 30cm to 80cm. Nobody is predicting that sea level will fall or remain unchanged over this time.
Council has assumed a worst case scenario, of an 80cm rise by 2100.
It’s tough making predictions, especially about the future.
Mike Cleeland B Sc(Ed), Geology Teacher, Bass Coast Adult Education Centre. Data Source; NASA Global Climate Change Indicators.