Sea levels

Along the south coast of England, sea levels have risen by 16cm since 1850 (Environment Agency, 2021). This is mainly due to thermal expansion as a result of increasing sea water temperatures and increased amount of water in the oceans as a result of land glacier melt (NASA, 2021). Sea level rise can be partially attributed to slowly tilting land in the South of England (IPCC, 2021).

Sea level will continue to rise to 2300 under all climate change projections. Even if greenhouse gas emissions stopped immediately, sea levels would still rise. This is because the ocean warms more slowly than the land and atmosphere, so is essentially ‘catching up’ with the new global temperatures, expanding as it warms.

Global termperatures are important. Sea-level rise will be 10 centimeters higher at 2°C than at 1.5°C (EA, 2021). Sea level projections from the IPCC by 2100 are as follows:

0.3-0.6m under very low GHG emissions scenarios, 0.4-0.8m under medium GHG emissions scenarios, and 0.6-1.1m under high emissions scenarios (the current global trajectory). What this looks like has been mapped here. NB: this mapping tool may not take into account coastal defenses or salt marshes (which mitigate against sea level rise by absorbing water). However, It does use very accurate mapping technology.

What it means for us

Whilst the cliffs at Milford have high elevation, higher sea levels will mean a loss of beach area and increased cliff erosion. Higher sea levels also mean higher waves, particularly during a storm, increasing the impact of storm surge events.

Current high tides cause flooding around Sturt pond and Saltgrass Lane. This will increase as sea levels increase.

Keyhaven is currently largely protected from flooding by the sea wall defense and flood gate at Saltgrass lane. However, under high emissions scenarios (current global trajectory), sea levels at high tide would be touching the top of the sea wall (and over the height of the flood gate) by 2120. Under rising sea levels and increased pressure from higher waves (and more frequent storms) as a result of climate change, the sea wall defenses are likely to fail by 2028 (EA).

Saltmarshes: the saltmarshes at Keyhaven and Lymington provide excellent coastal flooding and erosion defense as they absorb wave energy and rising waters. One hectare of salt marshe can capture two tonnes of CO2 per year. The Keyhaven marshes have been declining in area and quality since 1970 due to sea level rise, resulting in a loss of habitat for a range of rare marine species. Natural England and The NFPA have identified the New Forest salt marshes as one of the most vulnerable ecosystems in the UK under a warming climate.

What can we do?

The Environment Agency is working with NFDC to plan appropriate upgrades to our coastal defences. Look out for public consultaions and information on the NFDC website.