Warm sea good and bad news for Kiwis

Near-record sea surface temperatures are being described as ‘‘off the charts’’ and New Zealand could be on track for a record year, weather forecasters say.

A La Nina pattern and higher than normal atmospheric pressure are warming sea surface temperatures by more than 6 degrees Celsius in some areas, compared with the average for this time of year, bringing warm weather to New Zealand.

La Nina, a major systematic global climate fluctuation, influences sea temperatures in our part of the world but forecaster Ben Noll from the National Institute for Water and Atmospheric Research (Niwa) said there were other factors driving the temperature higher.

‘‘La Nina sits in the background as big driver of the change but it’s at the top of a pyramid of other factors,’’ Noll said.

Higher pressure

‘‘One of those is we have much higher atmospheric pressure than normal which has a large effect on conditions,’’ he said.

Higher pressure creates tranquil weather which calms conditions over land and sea, and leads to less wind.

‘‘Winds are what churn up the sea and bring colder seas to the top, and with high pressure you don’t get that mixing so the sea at the top is stagnant and is heated more effectively by the sun with no storms mixing it up.’’

During La Nina events, the trade winds strengthen, and the pattern is a more intense version of the normal conditions.

‘‘But this year the intensity has turned up several notches to what we have previously seen,’’ said Noll. ‘‘This year is off the charts, truly exceptional.’’

He believes we could be on track for a record year as sea surface temperatures are rivalling previous boom years in 2007 and 2010.

‘‘The difference in the average is higher, and in some places much higher this time around. The difference above average is 2C but some isolated areas located west of New Zealand have 6.5 degrees higher than the average.’’

It was an impressive and extreme difference when only a year ago the temperatures for this time of year were between 12C and 14C, he said.

‘‘At between 18C and 20C, the east coast of Australia and the west coast of New Zealand have the warmest anomaly on the globe right now.’’

It could also mean fish that enjoy warmer water – such as snapper, albacore tuna and kingfish – stay in New Zealand waters longer.

Fish stocks

Niwa fisheries scientist Malcolm Francis said fish such as snapper spawned in the warmer water, ‘‘so that could start earlier if the temperatures continue to rise, and ultimately improve our snapper fish stocks’’.

However, it would take about four years for the snapper to mature before the effect could be measured, he said.

The Ministry for Primary Industries is set to review snapper numbers over the next three years by electronically tagging 100,000 of the fish – a decision welcomed by experts from various fishing sectors.

Albacore tuna is a common fish trawled for by vessels off the West Coast, as they move from Auckland down to Westport.

Kingfish and kahawai also enjoyed the warmer waters, he said.

‘‘We usually see them in the South Island in autumn but that may happen earlier this year.’’

However, it could negatively impact on some species that prefer cooler water, and on land the warmer conditions could continue to plague farmers.

Saving water

While the warmer weather is good news for fisherman and beach goers, it could be bad for those watching our water usage.

The interior of Southland, Otago and Canterbury is expected to see the driest start to summer since 1990, and Wellington has a sprinkler-use ban to save water – a move unusual this early in summer, and water saving calls have gone out.