KEY POINTS:
On the bridge of the Tangaroa, Stu Hanchet is surveying a pancake ice panorama. The Niwa research vessel is a curiosity for the penguins and seals watching it glide gingerly by. Black and white Antarctic petrels and the occasional giant petrel come and go, the ship's resident skua
hovers.
Penguins, seals, even whales, have ceased to be a curiosity to the 26 scientists and 18 crew on the Tangaroa, which is undertaking the biggest ever biological survey of the Ross Sea - the perilous stretch of Antarctic water administered by New Zealand.
It's freezing, says Hanchet, who leads the science project. Ice and snow showers have been constant companions since the Tangaroa reached the Ross Sea, six days due south of Wellington. On deck, scientists and crew work in temperatures of - 12C or - 13C, deploying and retrieving unwieldy sampling equipment which, like the samples collected, can quickly freeze.
The scientists left New Zealand's once-in-a-blue-moon summer on January 31 with hopes of finding the Ross Sea largely free of ice. They had planned to venture further south than ever before, deep into the sea's southeastern corner, and to sample marine life on the continental shelf of Antarctica.
Hopes were dashed. Just to get into the inner Ross Sea, the Tangaroa had to weave a course through 250 nautical miles of sea ice packed far more closely than is normal for this time of year. But the scientists knew beforehand that their best laid plans were at the mercy of the elements.
Despite the conditions, everyone on board is happy. With the mission just past its midpoint, the diverse collection of scientists is excited by the diversity of samples and data gathered. The cramped ship is filling with giant jellyfish with tentacles up to 4m long, giant starfish, sponges and sea spiders and wondrously adaptable fish. Many suspected new species and new varieties are among the fish and marine organisms hauled from depths of up to 1900m. A multicorer has collected sediment samples rich in microbes and invertebrates from the seabed down to 2300m.
The $4 million Ross Sea survey is New Zealand's contribution to the International Polar Year and the global Census of Marine Life. Both projects aim to provide baseline data for measuring the impacts of climate change while adding greatly to knowledge of Antarctic marine ecosystems and the drivers of variations in biodiversity. Samples and data collected will provide the NZ scientists with three years of research and add to the international effort to understand Antarctica before it is too late.
While the conditions thwarted ambitions on the southern shelf, the focus simply switched to slightly warmer waters in the western Ross Sea, off Cape Adare. The survey will go close to its optimistic goal of spending about 35days of the 50-day mission sampling. This week, however, was time to get out of the inner Ross Sea. Hanchet admits to being unnerved by watching grease ice forming on the surface and develop into pancake ice. "It's quite amazing seeing ice crystals forming in front of your eyes."
Voyage leader John Mitchell says the amount of open water in the inner-sea is shrinking. "We've decided we'll head out while it's still open enough to get out."
That means charting a path through ribbons of water flanked by ice, or pushing through the ice. "You get patches where you can go up to 10 knots, and then you're down to 1 or 2 knots pushing through heavy ice. In the lower decks you can definitely hear the ice scraping down the side of the ship and a shudder when it pushes aside a larger piece - but the noise is not excessive."
It may be the satphone, but Mitchell seems more circumspect than when we spoke in Wellington weeks before the mission. Then, he joked it would be his fault if Niwa's only research vessel was lost. Now, he's not about to let that happen (although even he must bow to the Tangaroa's skipper Andrew Leachman).
The ice conditions are probably the worst in the Ross Sea in 20 years, he says. Still, the ship got as far as 77 degrees south, about 100 nautical miles from the ice shelf.
The weather has been "typical of the Antarctic for this time of year," he says. "There were a couple of bad periods when winds got up to 40-50 knots and freezing snow stopped work for a while at one point."
Keeping electronic gear such as CTD (conductivity, temperature, density) machines operational is a challenge in such conditions. The solution: pour hot water over the equipment during deployment to prevent it freezing before it hits the water.
High winds and freezing salt spray have cloaked the ship in ice at times. This has meant chipping nets, sleds and other gear out of solid blocks of ice before they can be deployed.
"It was a real challenge to work in the southern Ross Sea," says Hanchet. "You would pick up an Antarctic silverfish [on deck] and it would freeze before you could start processing the sample.
"With most species, all we can do is sort as much as possible into similar groups and freeze or preserve them and take them back for identification."
But nothing unexpected has occurred. Everyone working on deck has enough warm and dry clothing and there are shelter areas for a reprieve. There is plenty of food - and the cooks do "an imaginative job with what they've got," says Mitchell.
There was little seasickness during a benign trip down. Satellite-based ice information is obtained from a Canadian company - "you look at the trends and soon work out where you can and can't go".
There has been personal tragedy to cope with. Two weeks into the voyage, Niwa oceanographer Julie Hall received news that her scientist partner Trevor Atkins was killed when his glider crashed at the national championships at Waharoa. While it might have been possible to get Hall off the ship, she opted to stay and her colleagues rallied around. Atkins' funeral will be held on her return.
Hanchet says collaboration between the scientists - from Niwa, MFish, Waikato University, Victoria University, Te Papa, the US and Italy - has been a highlight of the voyage. "We've all had a common idea of where we want to go with the voyage and the co-operation among scientists has been very good. We've had to make some tough decisions at times about what we can and can't do. But looking back, I wouldn't change the way we've carried out the survey so far.
"The crew have done an excellent job as well in being able to switch quickly between gear and reducing down time while we're waiting for gear to be deployed."
The survey is comprehensive - taking in the continental shelf and slope and the abyss and sampling at a range of depths. At selected "core stations" the entire water column from surface to seabed is sampled. The specialised equipment includes wide-beamed trawl nets, a bottom-skimming sled with fine mesh nets attached, rough bottom trawls, the multicorer for sampling sediment and CTD and Niskin bottles for sampling the properties of sea water.
"Deploying [up to] 10 pieces of gear over the side in quite a short period of time - it has run like clockwork a lot of the time," says Hanchet. "Everyone knows their job - they get out there and bring in the camera system, then next thing we're putting down the bottom trawl or the beam trawl, then that comes up and we put down the bottom corer ...
For Hanchet, a highpoint has been a successful acoustic survey of Antarctic silverfish - small fish which play a vital role in the Ross Sea food chain. "They are fed on by everything from whales, penguins and seals to large fish including toothfish and ice cods. Having some idea of their abundance and distribution is going to be vital to the ecosystem model which we are trying to build."
Using a combination of frequencies, the scientists were able to distinguish the silverfish from the equally abundant krill and deploy trawls to come up with samples of both - a first for a Ross Sea survey.
The ship's high-tech camera gear has also proved its worth in showing the abundance and distribution of bottom-dwelling (benthic) species in the lightless depths. "With the video camera you can see species in their true colours and habitat, and their spatial distribution. By deploying beam trawls you can compare the samples with what's on camera."
The gear is in frequent need of repair, and not just because of the freezing conditions - the rocky seabed off Cape Adare took a harsh toll on the bottom trawl nets. The rocks, some huge, originate from mainland glaciers and are deposited by drifting icebergs. One, weighing 2 tonnes, was hauled up in the beam trawl.
All going well, the Tangaroa should today be drawing clear of the sea ice and heading for the mission's final phase - surveying the abyssal depths down to 3500m and volcanic seamounts just north of the Ross Sea. Hydrothermal vents around seamounts belch out a mix of sulphurous minerals, gases and sea water at up to 300C but extremophile species somehow survive. Increasingly, scientists believe they hold the key to the origins of life on Earth.
To follow the mission:
Go to www.fish.govt.nz and click on "IPY CAML voyage" under Hot Topics
