Kiwi scientists are sampling Sub-Antarctic trees to better understand the mysterious Antarctic Convergence

Want to hear something encouraging about climate change?

How about the reassuring fact that of total carbon dioxide released into the atmosphere, about half gets re-absorbed by plants and seawater.

And it also seems positive that we New Zealanders have, "The Prince of all natural Carbon Sinks", right in our backyard.

This is the mysterious natural climate engine, located deep down in the Southern Ocean, which is called the "Antarctic Convergence".

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Campbell Island is located in the
Campbell Island is located in the "Furious Fifties", where violent westerly winds interact with currents to push rivers of seawater to great depths. Photo: Paul Charman

Kiwis are leading the way in attempts to understand this phenomenon, but more about that later.

First, let's pay homage to this remarkable climate feature.

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Campbell Island keeps its secrets

It's not much to look at, perhaps resembling the outline of a massive fried egg, with the continent of Antarctica as its yoke.

But what takes place within this wobbly circle at the base of Planet Earth is truly amazing.

At latitudes of the so-called "Furious Fifties" (50 degrees below the equator) violent westerly winds interact with currents to push rivers of seawater to great depths.

Thousands of years later, these waters work their way back to the surface, up-welling further south, closer to so-called "Screaming Sixties" latitudes.


Scientists disagree

Paul tries his hand boring into the spruce, the only tree growing on Sub-Antarctic Campbell Island. Photo: Debra-Rose Charman
Paul tries his hand boring into the spruce, the only tree growing on Sub-Antarctic Campbell Island. Photo: Debra-Rose Charman

Scientists believe the process strips vast amounts of carbon dioxide from our atmosphere, but disagree over whether the process is slowing or accelerating.

"At present we really don't have enough data to observe it properly; studies using distinct mechanisms have arrived at contradictory conclusions," says GNS senior scientist Jocelyn Turnbull.

"Some have have concluded, 'ah well, climate is changing and westerly winds are increasing and that's causing more up-welling of deep waters in the southern ocean'."

And that would mean that overall the Southern Ocean is taking up less carbon than it was previously.

"Others have looked at things with different data modelling and concluded the opposite. They have said there is less up-welling, so therefore the Southern Ocean can take up more carbon.

"We just don't know which conclusion is correct, but with the problem of global warming literally hotting up, we've decided we better find out."

The Marsden Fund is funding research which is a collaboration between Jocelyn Turnbull at GNS Science and Sara Mikaloff Fletcher at NIWA.

GNS will use radiocarbon (the radioactive isotope of carbon used for carbon dating) in an attempt to see what's really going on.

Ms Turnbull says the older deep waters coming up to the surface are depleted in radiocarbon, as having been away from the atmosphere for thousands of years much of it has decayed away.

So when this water comes to the surface, it can exchange with the atmosphere and decrease the amount of radiocarbon. This will be proportional to how much up-welling there is.

To determine if the (rate of) up-welling is changing it is necessary to measure radio-carbon at a latitudinal gradient across the Southern Hemisphere.

But how?

"The problem we have is that few sites in areas required have been measuring this data over the past 30 years. There's one in Wellington that is 60 years old and a few sites further south which have been in operation for about 10 years."

Ms Turnbull says the answer is to use tree rings.

"Trees take up CO2, using it to grow. Their growth rings record the radiocarbon content of the carbon dioxide the tree uses to photosynthesize.

"So on this project we're collecting tree rings, cutting them up to measure their radiocarbon content.

"We'll sample trees growing near as possible to the latitude of the 50s - from New Zealand and Chilean Sub-Antarctic Regions.

"This will tell us what the radiocarbon content of the atmosphere in the Southern Hemisphere has been over the past 30 years.

"It could prove that over time the Southern Ocean has been taking up more carbon, or maybe less. Either outcome could affect our future, by indicating the rate climate change is happening."


Beeman Base

Beeman Base was the scene of substantial scientific research projects from about the mid 1950s till the mid 1990s. Photo: Paul Charman
Beeman Base was the scene of substantial scientific research projects from about the mid 1950s till the mid 1990s. Photo: Paul Charman

Earlier this month I accompanied Ms Turnbull when she sampled the historic Sitka Spruce at Camp Cove which, oddly enough, is the only tree on Campbell Island.

But to me the elephant in the room was Beeman Base - a facility on Campbell Island originally designed for climate research - is now little more than an empty shell.

The facility, which once boasted accommodation for 20 scientists and technicians, was automated in the mid 1990s.

In order to save money and avoid liability the owner of the base, MetService, has demolished the wharf and stripped out facilities, effectively putting the base into mothballs.

True, Jocelyn and her colleagues currently do not need to live and work in the deep south.

But, as climate change accelerates, the potential for this base to be used once again to monitor aspects of climate change seems obvious.

I'm told a permanent research station at Campbell Island, which could collect air samples throughout the crucial winter season, would be ideal.

DoC spokesperson Jo Hiscock says a final decision (on whether to demolish or retain Beeman Base) will not be made on this until after this summer season.

"A trip to the base is planned in March-April and we're not planning on looking into this issue until after then," says Ms Hiscock.

"Weather permitting, during the March-April trip, DoC and Met Service will be removing the balloon shed and tidying up around the base.

"The Southern Ocean is vast, and we are not sure what role Beeman Base might play (in climate research) at this stage."

But what is significant to me is that the term "no decision" often seems to mean "no money".

In other words, "no future" (beyond being a museum piece), for a facility which could be of enormous strategic importance to New Zealand scientific research in the era of climate change.