More than a dozen NIWA scientists are heading to Antarctica in the next couple of months as the crucial weather window opens for the summer season of research above, on and under the ice.

It's a busy time for the scientists who need to make the most of the coming months when the harsh environment is at its most hospitable.

The largest NIWA effort this year involves seven staff conducting marine ecology experiments under the ice at a coastal site in McMurdo Sound. They will set up camp 100km from Scott Base at Granite Harbour where they will live for a month.

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The group, which leaves on October 23, comprises scientists and specialist divers who go under the sea ice to take samples and conduct a range of experiments.

Drs Drew Lohrer, Vonda Cummings and Neill Barr have developed under-ice chambers in which the temperature and acidity of seawater can be manipulated and controlled, enabling the team to measure the effects of specific changes on ecosystem processes such as primary production by algae growing on the underside of the sea ice, nutrient dynamics and the delivery of food from the sea ice to the sea floor. It is critically important to understand the effects of changes in seawater temperature and ocean acidification due to increasing atmospheric carbon dioxide that are part of a suite of environmental changes in the Antarctic.

Dr Lohrer says one of the outstanding aspects of diving under the ice – which can be several metres thick - is the clarity of the water in the Antarctic.

"The ice blocks out a lot of sunlight so it is dim, but there are very few particles in the water column. You can see for hundreds of metres underwater.

"If you look upward, the bottom of the ice is covered in crystals and golden-green algae which is just beautiful. And down on the seabed are lots of incredibly colourful animals in high abundance. You also get some outlandishly large organisms."

The water temperature is about -1.9°C which means each dive is limited to about 40 minutes and only two divers are underwater at any one time, with a third fully ready as a standby measure.

Divers access the water through a hole in the ice, which is first drilled and then enlarged by melting to enable a diver and their gear to pass through comfortably. The divers are tethered to the surface to make it easy for them to find their way back to the hole and to communicate via a series of tugs.

Dr Lohrer says he is excited about next month's trip which is funded by the Royal Society of New Zealand's Marsden Fund with logistical support from Antarctica New Zealand.

"We get to concentrate on the science for a solid month. There are no emails or phone calls to distract us. It's a fantastic environment and the scenery is outstanding, but we work extremely hard because our time down there is so precious – we fit in as much as we can while we're there."

Meanwhile, a team of NIWA's atmosphere experts is making the most of the sun's return to Scott Base to measure the Antarctic ozone hole. The critical time for this work is between August and November.

They have instruments located at Antarctica New Zealand's Arrival Heights atmospheric research laboratory which is located about 5km from Scott Base. In total they have eight instruments to maintain and operate, some of which there are only a handful spread across the globe. The measurements made at Arrival Heights are an important component of a global network of measurements looking at ozone loss and greenhouse gas trends. Event Leader Dan Smale says each highly specialised instrument needs an annual "warrant of fitness" and one this year requires "open heart surgery" which will be carried out in mid-November.

Mr Smale heads to the ice next month to train the Antarctica New Zealand science technicians to operate NIWA's equipment and ensure the continuity of 30 years of atmospheric measurements. It is highly specialised work that combines automatic measurements along with manual observations.

"Some instrument reconfiguring is required, there is some minor maintenance and a lot of on-site training of the technicians. It's going to a busy, but exciting time."

Also heading to the ice in early November is NIWA marine physicist Craig Stevens who is conducting a field experiment into ocean turbulence beneath the sea ice that surrounds the giant Ross Ice Shelf cavity.

The experiments, being done in conjunction with Callaghan Innovation and the University of Otago, will provide the fundamental physical elements that get incorporated into computer simulations of how the oceans around Antarctica are changing.

These are in high demand internationally as we seek to estimate the impact of a warming world on the polar regions and the likelihood of unlocking the vast Antarctic ice sheets and their massive potential for influencing sea-level rise.

"One of the big unknowns is what happens at the interface between the ice and the ocean. We need more information to help us understand the circulation working under the cavity which is important for a whole range of climate change processes."

Dr Stevens and his team will spend two weeks living in insulated shipping containers about 12km from Scott Base.

Want an insight into life at an Antarctic capsite? See our video, below.

Summer Camp - Extreme

Rod Budd
A diver under the algae-covered sea ice in the Antarctic. [Rod Budd]