Voyage to study New Zealand's hot tap
Go to the east coast of the North Island, and the climate will be about 1.2 degrees Celsius warmer, on average, than at the same latitude on the west coast.
The reason: subtropical water brought across the Tasman Sea on an ocean current known as the Tasman Front. It’s an extension of the East Australian Current – the playground of surfing sea turtles in the movie, Finding Nemo.
“The Tasman Front is New Zealand’s hot tap,” says NIWA physical oceanographer, Dr Phil Sutton. “It’s why sea turtles sometimes turn up at the Poor Knights Islands,” says Dr Sutton, “and why marlin can be caught further south on the east coast than the west.”
Dr Sutton is leading a voyage on NIWA’s deepwater research vessel, Tangaroa, which leaves later this week to study the Tasman Front.
The scientists will collect instruments which have been suspended in the current, recording its speed for the past year.
“We are trying to find out how strong and variable the current is, because it’s so important for the country’s climate,” says Dr Sutton. “This research should help us understand the role of the front in large-scale changes in the Tasman Sea, such as the so-called “warm blob” – an area which warmed markedly in the late 1990s, causing record high temperatures in New Zealand.”
While Dr Sutton will be investigating the modern-day current, NIWA paleo-oceanographer, Dr Helen Neil, will be supervising the drilling of cores from the seabed, collecting sediment dating back hundreds of thousands of years.
Tiny, single-celled animals fossilised in the mud act as a record of what happened to ocean currents in the past. “About 125,000 years ago, the world was warmer overall than it is now, but some patches of the globe may even have been cooler. We can find out the situation in New Zealand through analysis of traces of oxygen and carbon trapped in the fossils. This will give us some clue as to what we can expect from future global warming,” says Dr Neil.