Hot seas could be catastrophic
Climate change spells peril for marine life
It is official, the seas around New Zealand in 2018 were the hottest on record.
While it might sound nice for your summer dip, scientists are warning the warming waters — fuelled by climate change — could have “catastrophic” impacts on our marine life.
A record-breaking marine heatwave last summer was the key driver of 2018’s hot temperatures, with parts of the Tasman Sea as much as 6C higher than average at times.
Those scorching seas saw anomalies such as snapper in Fiordland, and Queensland groper around Northland. It also saw high mortality rates for both the salmon and mussel farming industries.
It comes after Niwa announced this week 2018 was the country’s second-hottest year on record.
Scientists say this year the sea was on track for another hot one, with the Tasman Sea and areas just off the east coast currently about 3C above average, and some a whopping 6C warmer than normal.
Just north of Napier the sea was currently 24C — 6C above the average of 18C for this time of year, and putting it on par with Sydney and New Caledonia, which were both experiencing slightly cooler seas than usual.
According to data provided by Niwa the average sea surface temperature for 2018 was 15.6C — 0.87C above the 1982-2010 longterm average.
These figures have been backed up by the United Kingdom’s Met Office, whose figures show 2018 was 1.8C warmer since their records began in 1854.
Niwa said 2016 was the second warmest year on 15.4C, and 1999 in third on 15.3C.
Since 2013 four of the six warmest sea surface temperatures on record have occurred.
New Zealand’s seafood sector — worth $4.18b annually to New Zealand’s economy — faced some stark threats from these rising ocean temperatures and marine heatwaves.
University of Auckland marine scientist Dr Andrew Jeffs said the changes in temperature could have “catastrophic” impacts on our marine ecosystem.
Last summer’s marine heatwave saw a high mortality rate for salmon in the Marlborough Sounds, causing millions of dollars in losses. In the Hauraki Gulf temperatures as high as 25C caused issues for the greenlip mussel farming industry.
“They were simply falling off the lines,” Jeffs said.
“Sea temperatures do naturally fluctuate, but very gradually and only a small amount. Most species only have a narrow range they can survive in.”
With temperature changes species generally moved within their range, whether further south or into deeper water.
“But when they can’t move, eventually we start to lose species.”
When under stress marine organisms are also more susceptible to disease.
“It basically puts the whole ecosystem under stress.”
Warmer seas could also attract new predators and competition for local species.
In Japan, a herbivorous fish wiped out an area of seaweed that had been a nursery for baby lobster.
Another factor was the changing of currents. New Zealand is being affected by the slowing down of the East Australia Current, which typically brought more tropical species here, and even baby packhorse lobster.
“We are starting to see disturbance to the natural marine environment, and there is more to come,” Jeffs said.
“We have triggered the system and we are not slowing down, still putting more C02 in the atmosphere. The ecosystem changes could be catastrophic.”
It was not all bad news however, with some species thriving in the warmer waters.
“We know snapper breed really well in the Hauraki Gulf in warm summers, so, after last year’s marine heatwave, we will probably have a bumper crop in about four to five years.”
The Moana Project, led by MetOcean Solutions’ chief scientist Professor Moninya Roughan, was awarded an $11.5m Government grant last year to research New Zealand’s marine environment in a time of rapid ocean warming.
Niwa meteorologist Ben Noll said last year’s record sea temperature was down to three factors.
The first was persistent high pressure systems, meaning plenty of sunlight to warm the top of the water, and light winds to prevent mixing with the cooler, deeper water.
The second were prevailing northeast winds, driven by La Nina, bringing warm air down from the tropics, and a corresponding lack of southerlies.
Sitting on top of it all was climate change, which Noll said was providing a “long tail wind” to water temperatures.
AUniversity of Canterbury glaciologist has navigated a second expedition across the world’s largest ice shelf to enable vital insights into Antarctica’s vulnerability to climate change.
Dr Dan Price recently returned to Scott Base after making a six-week 1100km traverse of the enormous Ross Ice Shelf, to reach a remote and wild area called the Siple Coast.
Here, where the West Antarctic Ice Sheet lifts off the seabed and starts to float, scientists could find tell-tale signals of conditions that led to the retreat of glaciers and sea-level rise.
A research team led by renowned Antarctic scientist Professor Gary Wilson of Otago University surveyed the area using a gravity meter and explosives to trigger seismic waves.
But reaching this important spot had been fraught with difficulty – and attempts to get there by aircraft failed.
That left Price and a small team to try forging a path across some of the most perilous terrain on the continent in the largest Antarctic traverse since the Commonwealth TransAntarctic expedition in the 1950s.
While he’d spent several seasons on the ice as a research scientist, last summer was his first in an operations effort for Antarctica New Zealand.
“I got approached to plan a route across to the Siple Coast because no one has ever driven to it,” he said. “There are sections that are heavily crevassed, but the surface of the ice shelf is flat and white — these crevasses are completely hidden from the naked eye.”
Back in Sir Edmund Hillary’s time in Antarctica, such a journey would have involved peril at every turn.
Each year, the France-sized ice shelf stretches by about 400m, carving past the McMurdo Ice Shelf, which is moving an annual 50m. This created a “shear zone” where the ice shredded and left deep crevasses later concealed by snow.
“Without technology to help you, trying to find a path over this kind of landscape would just be about luck — you might try to read the terrain, but in certain areas that doesn’t tell you anything at all.”
Fortunately, the team was able to plot a route with TerraSAR-X, a satellite mission operated by the German Aerospace Centre (DLR). Microwave energy sent out by the satellite interacted with the surface of the ice and bounced back to space, allowing scientists to effectively take an X-ray of the shelf and its hidden traps.
“We can use this data to weave in and out of the hazards — without it we’d be navigating a minefield blindfolded.”
The team nonetheless had to take their own precautions.
One of their three PistenBully vehicles, often used as snow groomers on Kiwi skifields, was fitted with an 8m boom with radar technology that constantly scanned the ground ahead of them.
“You could monitor it on a screen in the vehicle in real time – and if a crevasse was coming up, you had a 5-second window to stop.”
The pre-plotted path proved reliable enough that this didn’t happen.
This season, Price and colleagues repeated the trip — this time to carry out gear for Wilson’s team — before carrying on another 150km to a US station at Siple Dome.
The trips could be exhausting, and not just because much of them were spent constantly focused on a screen.
“You drive for 10 to 12 hours a day, and then you sleep in the back of our vehicles, and you kind of get fatigued mentally.”
The weather was generally settled on the second expedition and temperatures reached as low as -19C.
“When we left base on the first traverse it was -40C; in those conditions the vehicles don’t work properly and everything becomes more difficult,” he said.
“On the way back, the worst conditions were when it was basically white-out, because you’ve got zero ground-definition you just feel like you’re floating.
“The horizon blends into the ground, you can’t see anything, and you’re navigating by GPS, which gets really tiring.”
But Price — a scientist who is passionate about climate action, and who made an awareness-raising odyssey from Antarctica to France in the months ahead of the landmark 2015 UN summit in Paris — felt satisfied to be aiding vital research.
The surface of the ice shelf is flat and white — these crevasses are completely hidden.
Dan Price
“Attempting to understand how the Ross Ice Shelf is going to respond to warming is a massive question, because it’s buttressing the incredibly vulnerable West Antarctic Ice Sheet and a huge chunk of the East Antarctic Ice Sheet,” he said.
“You’re talking about several metres of potential sea level rise that is being held in place, and the data that will come back from the Siple Coast will be extremely valuable.
“Yet, in the end, it all comes back to climate action. We can do the science and then say the sea level is going to rise by a specific amount, but if no one actually does anything about it, we’re still in the same position.
“So I think it’s all about ensuring that the urgency surrounding this science is effectively communicated to the right people and that we ultimately do the right thing — that’s to decarbonise as quickly as we can.”