Rising sea level
Our region's seas will continue to rise as greenhouse gas emissions increase and the earth's climate warms.
Sea level rise happens because rising temperatures warm ocean waters and make them expand, and because more water is being added to the oceans from melting glaciers and ice sheets. The melting glaciers in the Southern Alps are part of the process driving sea level rise, although scientists believe we can still save our high-altitude glaciers if we act now.
There are uncertainties about how fast the sea will rise and when it might reach certain levels, as it depends on greenhouse gases, human behaviour and inter-linked natural processes. Scientific projections therefore cover a range of possible futures.
In 2019, the Intergovernmental Panel on Climate Change advised that globally, sea level has risen by 1.5 millimetres each year during 1901-90, accelerating to 3.6 millimetres per year during 2005-15. Measurements taken at Lyttelton confirm this is happening here.
Although sea level rises and falls naturally depending on the Earth’s climate – the ocean was few metres higher 125,000 years ago and 120m lower 20,000 years ago when ice sheets were super huge – scientists agree that greenhouse gas pollution is a significant driver of the change we are seeing now.
Projections show that sea level could rise by up to 30 cm in the next 30 years, and by up to 80 cm by the end of the century for the Waitaha/Canterbury region.
The effect on our coast won't be like filling a bath, with the water coming up in a tidy line. Low-lying land is more exposed, like the parts of Christchurch that sank during its earthquakes.
Although the picture of how different parts of Waitaha/Canterbury will be affected by sea level rise is still being developed, some communities are already affected.