A moderate marine heatwave is predicted in Cape Reinga/Te Rerenga Wairua for February 24 to March 2. Photo / File
A moderate marine heatwave is predicted in Cape Reinga/Te Rerenga Wairua for February 24 to March 2. Photo / File
If you think the ocean has felt unusually warm this summer, you'd be right.
What you've felt is a marine heatwave, defined as an extended period of extremely warm ocean temperatures.
New data from MetOcean Solutions shows coastal waters in many parts of Aotearoa New Zealand have been warmer than usual for increasingly longer periods of time, and forecasts predict these conditions will persist.
This is a concern for Northland where marine heatwaves can have disruptive implications for marine life and marine industries.
MetOcean is helping understand and predict these heatwaves through a new initiative called the Moana Project - a large ocean research endeavour funded by the NZ Ministry for Business, Innovation and Employment (MBIE).
The project aims to provide information that supports the sustainable growth of the seafood industry, science research efforts, iwi initiatives and how to manage our marine environments.
Moana Project is breaking new ground in terms of forecasting these heatwaves and making the data freely available to all.
Dr Carine Costa, a Moana Project oceanographer from MetOcean Solutions, said according to the data, this summer's marine heatwaves were far from over.
"Over the coming week, we're expecting marine heatwave conditions to continue in Cape Reinga and the North Island's west coast, among other parts of the country," Costa said.
She said the warm sea temperatures were being caused by a combination of factors.
"In some areas, warm air masses, light winds and sunlight heat up the surface waters," Costa said.
"In other areas, the marine heatwaves are caused by ocean currents moving warm water masses into areas they don't normally reach."
According to Moana Project oceanographer Dr Robert Smith, this is important because it is the temperatures at depth that most affect seafloor marine species such as crayfish, pāua and coastal finfish.
"So far in Northland, the strongest effects have been seen in waters off the Hokianga, though all of the region's waters have been in a marine heatwave state almost continuously since November, with temperatures about two degrees Celsius higher than usual," Smith said.
"Previous marine heatwaves have triggered widespread mortality of marine species, changes to commercial fish stock and the need to restrict or even close fisheries due to disease and harmful algal blooms encouraged by warmer water."
The Moana Project uses advanced ocean models to predict when and where marine heatwaves will affect coastal and oceanic waters.
These forecasts can support a range of management actions in the huge variety of industries that rely on marine ecosystems.
A recent peer-reviewed study published in the journal Science, one of the world's top academic journals, showed large, impactful marine heatwaves have become over 20 times more frequent than a century ago due to human influence on the climate.
"Marine heatwaves have always occurred and will always occur, as an intrinsic part of the climate system," Smith said.
"However, as global ocean temperatures have increased, these extreme events have become considerably longer lasting and more intense in all of the world's oceans.
"The threat to our coastal ecosystems, aquaculture and fisheries is real and mass mortality events will affect many traditional activities we all enjoy."
This summer saw among the strongest marine heatwave conditions New Zealand has seen in the satellite ocean surface temperature record that began in 1981. Photo/ Supplied
Northlanders may recall the loss of hundreds of thousands of mussels at this very time of year back in 2020.
The devastating event on the west coast of Northland was attributed to extremely low spring tides combined with marine heatwave conditions and an atmospheric heatwave.
"What's also concerning is that a new study released last week in the journal Frontiers in Climate has shown that, under a high emissions scenario, marine heatwave conditions could become permanent year-round in Aotearoa New Zealand coastal waters by the end of the century," Smith said.
Furthermore, because our climate is strongly controlled by conditions in the oceans, warmer oceans will inevitably lead to changes in wind and rainfall patterns.
Smith said this meant cyclones coming over marine heatwaves would be potentially fueled with even more heat energy, leading to a more damaging wind event.
"The reduction of global carbon emissions is key to minimising the risk of future large marine heatwaves around New Zealand and the substantial ecological, social and economic impacts they bring for our marine ecosystems, industries and coastal communities," Smith said.
"Alongside the challenges though, there are also opportunities to innovate.
"For example, scientists at Otago are currently working on breeding heat-resilient kelp forests."
