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Predicting the impacts of sea level rise

New Zealand’s ability to adapt to climate change depends on accurate predictions about what will happen — and what we can do to manage the impacts. A five-year programme jointly led by Victoria University of Wellington, GNS Science, and NIWA aims to improve predictions about how sea level rise will affect our coasts over the next several hundred years.

Small house about to be engulfed by sea. Photo: Alan Blacklock

Some areas of Aotearoa's coastline rise or fall by 3-4mm a year. Photo: Alan Blacklock

The New Zealand SeaRise project will fill knowledge gaps that currently stop us from anticipating and managing the impacts and risks of future sea level rise. 

Predicting sea level change is complex. There is broad agreement that global warming is causing ice sheets and glaciers to melt and ocean waters to expand — and as a result, sea levels are rising and will continue to do so. But there are many uncertainties. 

It is not yet clear how rapidly Antarctica’s sea ice will melt, and changes to sea level will not be uniform across the planet. Our preliminary work suggests that sea level close to Antarctica’s coast will initially rise faster than the global mean. This local variability is partly due to the gravitational attraction between the ice sheets and the ocean, but also reflects the impact that changes in surface mass have on the shape of Earth’s crust. 

Tectonics also play an important part in forecasting local sea level change. Aotearoa’s coastline is constantly changing, with some areas rising or falling as much as 3-4 millimetres per year. SeaRise will use data from our national network of GPS receivers and information from radar systems to determine how much the land moves. These location-specific forecasts will help assess the impact on New Zealand’s coastal areas. 

We are currently investigating how rising seas will affect groundwater levels in south Dunedin. We are also working with iwi in Hawke’s Bay to examine how sea level rise might alter the distance that salty water can flow up coastal river systems and potentially affect important ecosystems. 

Change is inevitable, but excellent science can help us adapt. The projections generated through the SeaRise project will help assess the full range of impacts and solutions we need to deal with inevitable change around New Zealand’s vast coastline.