Better modelling of ocean currents in the Tasman Sea will help improve the accuracy of future climate change predictions, leading to effective decision-making on responding, adapting and thriving in a changing climate.
In recent summers, New Zealanders have experienced a series of marine heatwaves. While people may enjoy warmer water temperatures, most marine organisms suffer heat stress and the warmer water drives further changes in the weather, climate, fishing and aquaculture.
New Zealand’s climate and its climate extremes are highly affected by ocean temperatures and the interplay of heat and moisture over the Tasman Sea. Oceanic heat from the East Australian Current (EAC) heats up the Tasman. It "catches a fever" which can result in heatwaves and climate extremes over New Zealand.
This project is part of the New Zealand government’s National Science Challenge – Deep South: Changing with our Climate.
The current New Zealand Earth System Model (NZESM) doesn’t simulate the Tasman Sea heat transport as precisely as it could. Without significant refinements, researchers won’t be able to rely on future climate projections.
Researchers also need to resolve small-scale oceanic movements, such as ocean eddies. They influence large-scale ocean circulation, such as ocean gyres and the strong currents in the Southern Ocean. These large ocean currents transfer heat to the air, impacting the Southern Hemisphere climate.
Improved modelling of these currents means they’ll be better represented in the NZESM. Modelling will more accurately predict changes such as ocean and land temperature and related climate extremes.
NZESM builds on its UK counterpart (UKESM) and does a better job of simulating oceanic climate extremes such as marine heatwaves around New Zealand. To date, New Zealand’s oceans have been poorly represented in global climate models.
Researchers have now “tweaked” the ocean model component of NZESM. The result is better simulations of New Zealand’s present-day ocean temperatures, salinity and currents, and therefore the ocean’s bio-geochemistry.
Better knowledge of future climate extremes is vital for effective decision-making on how to respond, adapt and thrive in a changing climate.