The data and trends on sea level are outlined below as part of the climate change section of the London State of the Environment Report 2010. Sea level rise will be one of the contributing factors to an increase in flood risk in London.
About the data we used
For this indicator we have used sea level data from the Proudman Oceanographic Laboratory.
The data is obtained via the UK National Tide Gauge Network, which is run by the Tide Gauge Inspectorate. It is then quality controlled by the British Oceanographic Data Centre.
Data is available for 44 sites around the UK. We chose representative sites at Dover, Sheerness and Southend because of their proximity to London. However, data series ends in 2006 for Sheerness and in 1983 for Southend. Dover has current data up to 2008.
The indicator is measured using the Revised Local Reference (RLR). This is a datum level relative to which the mean sea level is approximately 7,000mm. This has been defined by the Permanent Service for Mean Sea Level.
Overall trends on sea level
Sea level has increased over time at all three sites near London. See the charts below for more detailed information.
There is some occurrence of isostatic rebound – the rising of land in the northern UK, post glaciation, which is causing the south east corner to sink - so the actual sea level rise is slightly less than forecast.
A Defra and Environment Agency study in 2007 outlined that actual sea level change (minus land level change) around the Thames Estuary is between 0.9-1.2mm per year.
Dover – sea level change
The chart above shows that the sea level at Dover has risen by 682mm in the last 40 years – between 1968 to 2008. There has been an average increase of 2mm per year.
Sheerness – sea level change
This chart shows that at Sheerness the sea level has risen by 248mm between 1900 and 2006. There has been an average increase of 2.3mm per year.
Southend – sea level change
At Southend sea level has risen by 91mm over 50 years – between 1933 and 1983. There has been an average increase of 1.8mm per year. There is no further monitoring data after 1983 at Southend.