China is preparing to build its sixth research station in Antarctica, expanding into Marie Byrd Land — a remote, little-studied stretch of the continent's west.

It has some experts and politicians worried.

Independent senator Jacqui Lambie is among those concerned about Australia's defence priorities.

"Five bases have already been built, and China claims there is no geopolitical motive," she said.

"Open your eyes, [Department of] Defence."

Whether that alarm is warranted depends on who you ask.

China says the new base, which it plans to build next year, will support research into climate change, ice sheets and marine systems.

And it is far from the only country with a significant presence.

The US operates three permanent year-round bases. So does Australia, which claims 42 per cent of the continent, while Russia has five year-round stations.

But experts warn what matters most is not the station itself.

It is what the project might signal about China's deepening influence inside the institutions that govern Antarctica.

Military use or just science?

Jiliang Chen, a lecturer in Antarctic law and governance at the Institute for Marine and Antarctic Studies at the University of Tasmania, sees the new station mainly as a matter of prestige.

"Building a station is China capitalising on its strength in this strategic game," Mr Chen said.

China's new station is being developed as per the Antarctic Treaty System's environmental assessment procedures.

Under the Antarctic Treaty, member states cannot veto a proposed new station.

The treaty was originally signed by 12 countries in 1959 and designed to ensure the use of the area for peaceful purposes only and the protection of the environment.

Mr Chen said a stronger physical presence helped consolidate China's role in future decisions on the continent.

"It gives people one more thing to be proud of, scientists more facilities to do research, and more projects to plan," he said.

One complication is that equipment such as satellite systems, communications hardware, aircraft and drones serve civilian research and can easily be adapted for military use.

That dual-use capability is why Mr Chen believes inspection and transparency matter most.

Other experts are more suspicious.

Elizabeth Buchanan, a senior fellow at the Australian Strategic Policy Institute (ASPI), points to China's existing satellite ground stations and its Military-Civil Fusion policy, which enables civilian companies to develop or supply technologies for military use.

Her deeper worry is that China's spread of stations could eventually let it operate across Antarctica without depending on other countries.

"Polar power with serious polar independence means we have very little leverage left," she said.

Some say that framing is overblown.

The Antarctic Treaty prohibits military bases, weapons and new territorial claims, while permitting military personnel and equipment for peaceful purposes.

China's embassy in Canberra told the ABC it was "fully committed to ensuring its activities in the region strictly align with the Antarctic Treaty System".

Tony Press, the former head of the Australian Antarctic Division, said he believed mining and military fears were exaggerated, citing the cost and difficulty of moving people and equipment across such a hostile environment.

"Antarctica is a terrible place to fight a war from," Mr Press said.

Unlike China's year-round Quinling station, the new base would run only in summer, hardly the profile of a strategic outpost, Mr Press said.

Instead, he said China was making a geopolitical statement.

"China is obviously doing the old strategic thing of making sure they've got stations around Antarctica that demonstrate quite clearly that they are a big player in, and have an interest in, all parts of Antarctica," he said.

Working the system, not breaking it

Analysts say China is finding ways to become increasingly influential without breaking the rules.

China joined the treaty later than other countries, in 1983.

"China has always been nervous about natural resources and probably more hungry for economic growth," Mr Chen said.

Fishing is where this showed most clearly, he said.

China joined the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), largely because of its interest in Antarctic fishing, Mr Chen said.

Ms Buchanan pointed to the broader growth of China's fishing fleet and domestically built fleet of icebreakers as part of its "Polar Silk Road" strategy.

She said China was also preparing to unveil a nuclear-powered icebreaker, which she said would reduce its reliance on gateway ports such as Hobart.

The Chinese Communist Party's latest high-level five-year plan aimed to expand capacity in high-seas fisheries, and polar fisheries were now getting similar attention, Mr Chen said.

Emperor penguins caught in the middle of geopolitics

China has generally opposed new marine protected areas in Antarctica.

Nearly half of Antarctica's 60 emperor penguin colonies have suffered increased or total breeding failure since 2016 as sea ice they depend on has retreated, according to researchers from the British Antarctic Survey.

Efforts to list them as a Special Protected Species have stalled at CCAMLR, blocked by China and Russia.

The stated objections cite insufficient scientific evidence, or argue that such a listing would address a symptom (habitat loss) rather than its underlying cause of climate change, which sits outside the treaty's scope.

Lyn Goldsworthy, an adjunct researcher at the University of Tasmania's Institute for Marine and Antarctic Studies, said China was operating from a strategic perspective, and wanted to avoid restricting access to certain areas in case it had "certain aspirations" in the future.

Ms Goldsworthy added China appeared to join the conservation body CCAMLR for the purpose of fishing first, not marine biology or conservation.

Krill is another source of tension.

The tiny crustaceans are a primary food source for penguins and whales.

Next month's CCAMLR meeting, known as the "Krill Convention", will debate fishing limits.

China has a particular interest in Antarctic krill, which is increasingly valuable as an ingredient in aquaculture feed and nutritional supplements.

Krill products were pulled from shelves in Australian supermarkets after environmental campaigns, but China and Norway are pushing to raise the current catch limit much higher.

Ms Goldsworthy described years of stalemate.

"You have China saying, 'We don't believe in marine protected areas, you should give us our krill fishery'. Other countries are saying, 'No, we won't discuss krill fishery expansion until we've progressed marine protected areas,'" she said.

"There is now a deep distrust."

The underlying ecological concern that over-concentration of fishing in certain areas damages predator populations and habitats has become inseparable from the geopolitics around it, Ms Goldsworthy said.

One flashpoint was an area where heavy Chinese fishing activity overlapped with an Argentine-Chilean proposal for a marine protected area, she said.

Experts say Russia has also played a "disruptive" role, objecting alongside China to new marine protection sites.

'Treaty not about to topple over'

Indi Hodgson-Johnston, a senior lecturer in marine and Antarctic law and policy, describes a pattern of "quiet disruption" by China, but technically no broken rules.

"The treaty is not about to topple over. I can't see that happening," said Ms Hodgson-Johnston, who works at the Institute for Marine and Antarctic Studies at the University of Tasmania.

"There's disruption everywhere at the moment. I would say Antarctica is just not a special case," she said.

However, ASPI's Ms Buchanan warned consensus-based governance could just as easily mask a "holding pattern" while one party's capacity and presence grows.

"We can't continue to assume, blindly, it's all happening in good faith," she said.

"We need a dual-track approach that has some optimism in continued adherence to the treaty while crafting a mighty stick or plan B to balance China's expansive ambition in Antarctica."

The ABC has approached the Department of Foreign Affairs and Trade for comment.