Studying colourful images of an exotic form of Antarctic ice is helping a University of Otago-led research team gain new insights into the health of the Ross Ice Shelf.
Otago scientists have not only studied this form of ice, called platelet ice, in detail, in the laboratory but the international team has also constructed a century-long record of the condition of the major Antarctic ice shelf.
The first-of-its-kind dataset indicates that over the past century the ice shelf has remained largely stable.
By contrast, in recent decades several ice shelves elsewhere in the Antarctic have been thinning from below and collapsing, due partly to warmer water temperatures.
The researchers, led by Otago physics Associate Prof Pat Langhorne, have also been able to establish a continent-wide baseline for melt-refreeze processes at the bases of Antarctic ice shelves so future change may be measured.
Their findings were published recently in the international journal Geophysical Research Letters.
Instead of directly measuring the ice shelves, the team studied a signature in sea ice cores taken from the frozen ocean that surrounds the continent in winter.
This signature involves the presence or absence of platelet ice, which grows at the base of sea ice when super-cooled seawater flows out from under the shelves and into surrounding ocean.
''I'm delighted that it's got to this particular point,'' Prof Langhorne said of the research.
Melting at depth and refreezing in the shallower parts of an ice shelf was a natural process that had taken place over millennia.
In many places, very cold seawater - at the point of refreezing - flowed from under the ice shelf to the bottom of nearby coastal sea ice.
''The platelet ice this forms reflects lower temperatures at the base of the shelf which prevent its thinning.''
Being able to monitor the ''health'' of the bases of Antarctic ice shelves was vital because the shelves acted as ''corks'' that kept the ice, including glacial ice, on continental Antarctica from flowing into the ocean and catastrophically raising global sea levels, she said.
The research was being undertaken with other colleagues at Otago University and in Niwa, Canterbury University, York University in Canada, and the University of Alaska.
