We are in for sea level change
Carbon dioxide levels are continuing to rise and following the IPCC report in 2007 we can no longer escape the fact that sea levels are rising and it is due to global warming. With the majority of Australian’s living on the coast there is no doubt we are in for a sea change.
Sea level rises is two main ways. The first is through volume, for example when ice from glaciers melts and is added to the ocean. The second way is through thermal expansion. As the water in the ocean heats up it expands, thereby contributing to sea level rise.
A combination of sea level data from coastal tide gauges and satellite imagery used to estimate global average sea level from 1870 to 2005, shows an increase in sea level of about 3 mm per year. The rate of sea level rise relative to any given land mass may differ due to land movements. It is estimated that the relative sea level rose by 100mm between 1920 and 2000.
The two longest sea level records in Australia are from Fremantle in WA and Fort Dennison in Sydney. Measurements from these two sites indicate that as well as an increase in average sea level, there has already been a change in the frequency of storm surges during the 20th century, with extreme sea level heights being three times more prevalent during the second part of the 20th century. Storm surges result in increased erosion, with every 1cm of sea level rise accounting for one metre of erosion of the foreshore.
Due to the slow response by the oceans and ice sheets to sea levels will continue to rise even if CO2 is stabilised today. We need to act now.
It is not just million dollar waterfront properties at stake here