Millennia of snowfalls record past climates in the chemistry of their ice and the tiny bubbles of air trapped with them. When an ice core is extracted, its layers can be analysed to reconstruct a story about how the climate has varied over millions of years at that particular place.

Nancy has had a central and enduring role in establishing ice core research in New Zealand. When she arrived in 1999 for her PhD studies, there was no ice core programme here, and overseas, cores were only being taken from the interior of Antarctica.

“Until we started looking at the coastal regions, no one thought ice cores from there would be useful. We figured their position would make them really sensitive to interactions between the ocean, the ice sheet and the atmosphere.”

Her hunch proved to be correct and the Ross Sea region, where New Zealand has guardianship, turned out to be perfect for this new application.

“It’s a challenging environment but it gave us a niche to do some really important research. From that we made a case that we needed a facility here to do the work, rather than continuing to ship cores to our overseas collaborators.”

New Zealand’s high-tech ice core research facility was built in 2007 and is 1 of only 20 worldwide. Keeping the cores below -18°C degrees is essential to prevent deterioration and changes in the ice. This mandates a secure refrigeration system with power backups, a low-moisture environment and ultraclean facilities to protect the ice from contamination. A suite of analytical instruments is also housed in the facility.

A three-way collaboration between GNS Science, Victoria University of Wellington and NIWA established the ice core facility.

“This was a huge bonus because it gave us access to so much extra science capability. The facility’s cold conditions have also been used for research in volcanology, physics and other disciplines and provided exceptional scientific training for many postgraduate students.”

Nancy stresses the value of the ice. “There’s never enough and nothing is ever thrown away – it’s really precious. We have to push our analytical capabilities to use smaller and smaller samples. Every millilitre from a 2.5 tonne core is entered into a database and we account for every drop.”

The facility was central to the international Roosevelt Island Climate Evolution project. It set out to discern what the Paris Agreement target of keeping warming within two degrees would mean for Antarctic ice.

“We had to figure out if this much warming would commit us to a collapse of the Ross Ice Shelf and the West Antarctic ice sheet, and therefore significant sea-level rise. Using ice core records, we were able to see the extent of the ice shelf during a warm period 130,000 years ago when global temperature was 1–2 degrees higher than today.”