The sea is rising around the world and will continue to do so for more than a century. The Ministry for the Environment’s latest projections for New Zealand are that sea levels could be between 0.46 metres and 1.05 metres higher by 2100, depending on how quickly we manage to reduce global carbon emissions, as nations have pledged to do under the Paris Agreement. But new science by the NZ SeaRise team shows that melting polar ice sheets and local land subsidence could lift sea levels in New Zealand even higher. Our data will help us make better decisions about how to manage the consequences of rising seas in New Zealand.
NZ SeaRise brings together 30 local and international experts to improve predictions of sea level rise in New Zealand. Our data will be incorporated into the next Ministry for the Environment report on coastal hazards and climate change. From 2021, we will share detailed maps and models, based on different global sea level rise scenarios. This will provide more accurate and reliable information, crucial for council and government planners and freely available to the public.
Global sea level rise
The climate is changing and the world is warming. The oceans have taken up most of the additional heat so far, and as the water warms up, it expands. In combination with water from the melting of land-based ice, this causes rising sea levels. On average, global sea level rose about 19 cm between 1901 and 2010 (compared to sea level during 1985-2008), at an average rate of 1.7 mm per year. But this process is accelerating. From 1993 to 2016, global sea level rose at an average rate of about 3.4 mm per year. Climate trends and gravitational effects differ for each region and the seas don’t rise uniformly across the globe.
New Zealand sea level rise
The sea around New Zealand rose, on average, by 1.7 mm per year from 1900 to 2008. But at the same time, the land is going up in some places and down in others. We are putting both of these changes together to accurately predict total sea level rise at a local scale.
Rising seas have local impacts. This includes flooding, rising groundwater levels, coastal erosion, and salinization of wetlands and aquifers. We are working with partners – regional councils, iwi and government agencies – to look at specific local impacts of projected sea level rise.