One of the world's top scientific research ships is heading to Antarctica with 30 scientists from 11 countries on board to investigate climate and sea changes.
The 140m-long JOIDES Resolution is in New Zealand waters for about 18 months for a series of expeditions.
It has just finished investigating the Hikurangi subduction zone east of Gisborne and headed off for Antarctica on Sunday with a new group of scientists on board.
It operates under the 23-nation International Ocean Discovery Programme.
Voyage leader, Rob McKay of Victoria University of Wellington, said the aim of the latest expedition was to understand how the ocean and the ice sheets interacted.
"We want to find out what happens when you put warm water next to the ice sheets. How quickly do they melt? And what's the impact of that melt on the oceans?"
By drilling down up to 1km beneath the seafloor, the team will be able to get a glimpse into "greenhouse worlds" that existed 20 million years ago when carbon dioxide levels were similar to those currently in the atmosphere.
Antarctica acts as a giant heat-sink that helps regulate the temperature of the planet.
"If you change that, you're changing a major part of the global climate system. We're trying to understand what happened the last time that was changed."
If the West Antarctic Ice Sheet was to melt, as it has in the past, Dr McKay says the global sea level would rise about three metres.
The impact from the collapse of the much larger Eastern Antarctic Ice Sheet would be even more dramatic, as it contains enough ice to cause an estimated 20m rise in global sea levels.
"The consequences of that for coastal living, globally, are obvious, but we're also trying to understand the implications for the biosphere in the Southern Ocean. This is one of the largest biological habitats on the planet and we don't know how it will respond to these changes."
When the JOIDES Resolution returns from the Ross Sea in early March, it will stop at Lyttelton again and pick up a fresh crew of scientists and head back to the East Coast for a further probe of the Hikurangi subduction zone.
The area has slow-slip events - small bursts of movement on the fault lasting from weeks to months instead of seconds to minutes as in conventional large earthquakes.
They are poorly understood and scientists want to know what causes them and what relationship they have with large earthquakes.