Scientists surprised at how life under Antarctica's sea ice is changing

Sea ice around Antarctica is significantly dropping and beneath the ice, scientists are surprised by the rapid changes they're seeing in marine life in the Ross Sea.

A scuba team of highly experienced divers are carrying out experiments on the sea floor, but for two of the women, it's their first time diving under the ice.

Until recently, Hamilton marine ecologist Samantha Parkes and Auckland PhD student Jenny Hillman had never been to Antarctica.

They started their training on site at New Harbour, jumping in the deep end through 3.5m of sea ice into ocean water so cold, it's -2degC. Dry suits keep them from freezing during the 45 minutes they stay underwater, diving to a depth of 20 metres.

"It's starting to feel really natural," Ms Parkes told Newshub. "It's not kind of that shock of, 'Oh my god we're under the ice'."

The scuba team has placed chambers on the sea floor so they can closely study how the animals inside are reacting to a warming climate.

"The changes since 2009 have been remarkable," expedition leader and principal investigator Dr Drew Lohrer said.

Ice diving in Antarctica
Divers Samantha Parkes (L) and Jenny Hillman (R). Photo credit: Newshub.

In the past, the sea ice at New Harbour has been locked in place for more than a decade.

Now it's breaking out every few years, generating more food - micro-algae - for the underwater sea creatures to eat.

"The most surprising thing is how quickly the organisms - the animals - have responded to that food," Dr Lohrer said.

"The diversity is quite high and there's lots more organisms than we found last time we were here."

And while more food for these creatures may seem like a positive change, it may also mean more predators.

"There's always winners and losers when you change the conditions," Dr Lohrer said.

As the team studies those changes, the divers' safety is paramount. 

ice diving Antarctica
Photo credit: Newshub.

There's another dive hole in case a seal should claim the main one, and the divers are always tethered.

Ms Parkes and Ms Hillman are now on their 12th dive - and despite nerves early on, they're hooked.

"I was kind of 50/50, stupidly excited, but there was always that little niggle in the back of your brain thinking you're going through a hole in the ice," Ms Parkes said.

"Once I was down there, you just kind of forget it and it's amazing... it's like the landscape of another planet."

Ms Hillman said under the ice, it's a completely different world. The water is crystal clear and illuminated by the sun on the ice above.

"I've travelled a bit, but nothing compares to this," she said.

"It's really tiring because you come up from every dive shivering - and that's a good dive. We've had some bad dives with leaks... You can't move, your hand just goes into a claw and it takes ages - even with a stove - just to warm up."

Despite the cold, the team are looking forward to their remaining dives before they head home to New Zealand.

The data collected will keep them busy for at least a year, figuring out how the changing climate is impacting life under the ice.