Summer Series 2017 - A year of new knowledge
It’s been a year of discovery for NIWA scientists who now know more than they did 12 months ago – their top five discoveries for the year range from the bottom of the ocean to the top of the atmosphere.
Kaikoura canyon post earthquake
In January and February several NIWA scientists focused on finding out more about what happened to marine environment off Kaikoura following the November 2016 earthquake.
Marine geologist Dr Josh Mountjoy led an investigation to map offshore faults ruptured by the earthquake and to investigate changes at the head of the Kaikoura Canyon.
Dr Mountjoy said the amount of debris that cascaded through the canyon was massive.
“Some individual landslides are more than three times the size of the landslides that damaged the road to the north of Kaikōura.”
A second survey led by NIWA marine ecologist Dr Dave Bowden used cameras to survey the seafloor further into the arm of the canyon tp see if the damage to a renowned biodiversity hotspot.
They found while the structure of the canyon had remained intact, the mudslides had left no evidence of seabed life.
But in September the scientists went back and found signs of recovery in the seabed with evidence that juveniles of animals that once dominated the head of the canyon have now begun colonising the seafloor.
“The deep-sea communities might be recovering faster than we originally thought, with high densities of small organisms such as urchins and sea cucumbers in some areas of the canyon, as well as large numbers of rattail fishes swimming immediately above the seabed.”
The sounds of whales
The sounds of whales and dolphins rarely seen in New Zealand waters were recorded by a NIWA scientist in a pioneering underwater sound project.
In March the first analysis of work undertaken by NIWA marine ecologist Dr Kim Goetz was revealed following the deployment of seven acoustic moorings in Cook Strait to record the sounds of marine mammals.
Results showed that among more common whale species, the devices recorded vocalisations from Antarctic blue whales, Antarctic minke whales and several different beaked whale species that are rarely seen due to their extensive diving behaviour. These are likely to be the first recordings of Gray’s and strap-toothed beaked whales in New Zealand waters.
Dr Goetz said the project set out to look at what sounds could be heard in the waters of Cook Strait, in particular the man-made noise from vessels and industry, natural noise such as weather events and biological contributors such as whales and dolphins.
“Antarctic blues are coming into New Zealand waters. They have a very low frequency call so are being picked up further away but we’re really confident it’s not as far away as Antarctica.”
Dr Goetz says the data so far show that Cook Strait may be segregating different whale populations with Antarctic blues primarily heard on the east side.
“We have also picked up Antarctic minkes—it matches the time minkes are known to go into Australian waters but they have never been acoustically recorded here before.”
Ancient air bubbles tell story
Tiny air bubbles trapped in ice more than 10,000 years were able to tell scientists a story of what the world used to like and how humans have changed it.
Atmospheric scientist Dr Hinrich Schaefer was part of team that in August reported on a significant discovery about the emission of methane, a powerful greenhouse gas, that may alter how countries tackle reducing global warming.
The research challenges conventional thinking about the amount of methane seeping out naturally from oil and gas fields. The team found evidence that this is a fraction of what had previously been thought, meaning methane emissions from industrial fossil fuel use and extraction were far greater than realised.
Dr Schaefer said results showed the amount of methane escaping naturally from gas fields was three to four times less than previously estimated. Further, when the climate warmed in the past, methane was not released from ancient carbon reservoirs like permafrost or undersea gas hydrates, so would not be a factor in future climate change.
Dr Schaefer says the research has two main implications:
- If we know that the emissions are caused by industry or human activity, it means we have a chance to reduce them
- Huge natural stores of methane did not react to the end of the ice age and the team was hopeful that these reservoirs are less prone to warming.
Native forests suck in carbon dioxide
New Zealand’s forests and other land areas may be absorbing up to 60% more carbon dioxide than has been calculated, with much of this uptake likely occurring in native forests.
This research, revealed in February, and led by NIWA atmospheric scientists Drs Kay Steinkamp and Sara Mikaloff-Fletcher, indicates that New Zealand’s forests absorb much more carbon dioxide than previously thought, with much of the uptake occurring in the southwest of the South Island.
Carbon dioxide is a primary greenhouse gas and responsible for most of the human-induced warming in the atmosphere. Globally, carbon sinks, such as oceans and forests, have helped mitigate the effects of climate change by absorbing about half the carbon dioxide emitted by human activities over the past few decades.
“The story the atmosphere is telling us is that there’s a big carbon sink somewhere in the South Island, and the areas that seem to be responsible are those largely dominated by indigenous forests,” Dr Mikaloff-Fletcher said. Indigenous forests cover about 6.2 million hectares in New Zealand.
Dr Mikaloff-Fletcher says that was a very surprising result mainly because strong carbon sinks are expected when there is a lot of forest regrowth.
“Carbon uptake this strong is usually associated with peak growth of recently planted forests and tends to slow as forests mature. This amount of uptake from relatively undisturbed forest land is remarkable and may be caused by processes unique to New Zealand or part of a wider global story."
Winter? What winter?
A study produced in November showed New Zealand winters are a month shorter than they were 80 years ago.
NIWA principal climate scientist Dr Brett Mullan examined official temperature records from NIWA’s Seven Station Series which began in 1909 and uses climate data from seven geographically representative locations around the country.
Dr Mullan defined a winter’s day as one in which the daily average temperature was less than a selected threshold and then compared the number of days this occurred for two 30-year periods, the first from 1909 to 1938 and the second from 1987 to 2016.
Climate scientists consider 30 years to be the minimum amount of time to come up with a statistically meaningful long-term average.
The graphs showed that, if a threshold of 9°C was chosen, then there was an average of 100 days per year between 1909 and 1938 when the temperature was less than 9°C, compared to only 70 days per year between 1987 and 2016. Winter has contracted about equally from both ends.
Winter is conventionally regarded as occurring between June 1 and August 31 in the Southern Hemisphere – a total of 92 days. If defined using temperature, however, winter lengths will vary from year to year.
Dr Mullan said the number of frosts in New Zealand was also reducing in many locations, especially higher altitude inland regions of the country.