Sea ice in Antarctica breaking up and the fresh water underneath.

Weddell seals have returned to Antarctica's Scott Base to raise their pups for the first time since they were killed for dog meat in the 1960s.

As many as 20 newborns have been sighted at Pram Point, near to New Zealand's base on the ice – the largest number in 50 years.

Weddell seals, which can grow as large as 3 metres long and weigh about 500kg, often return to the same place each year.

The sea ice outside Scott Base was once home to the largest Weddell seal colony in McMurdo Sound.

The sea ice outside Scott Base was once home to the largest colony in McMurdo Sound.

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Zoologist Edward Wilson observed the large numbers during the Discovery Expedition to Antarctica, from 1901 to 1904, and wrote "they are so plentiful … amongst the ridges of broken ice about Pram Point".

Iain McGregor/Stuff Seals rest among the pressure ridges on Ross Island.

But as human activity increased the seals were "culled" to feed huskies and by the 1960s they had abandoned the site.

Antarctic marine mammal expert Dr Regina Eisert, who has studied Weddell seals in McMurdo Sound since 1996, has just returned from a seven-week research trip to Scott Base.

She said although the occasional pup had been born at Pram Point throughout the years, this season there were between 15 and 20.

Paul Ensor/Supplied One of the Weddell seal pups spotted near to Scott Base.

"That is a real step-change," she said.

"For the first time in living memory, Weddell seals showed up en masse, right outside Scott Base to give birth within sight of the station's living room."

The Weddell seal is among the best-studied marine mammals in Antarctica and a focal species for the Ross Sea region Marine Protected Area – the largest MPA in the world.

Unlike other seals, they live deep inside the fast ice that binds the coastline of Antarctica and the under-ice environment helps to keep them safe from other air breathing predators such as orcas and leopard seals.

The Weddell seals in McMurdo Sound give birth from around mid-October to mid-November, with "peak pupping" at the end of October.

Paul Ensor/Supplied Dr Regina Eisert observes an orca surfacing in Antarctica.

Eisert said the baby seals had "a very brief but intense nursing period" of about six weeks.

"During this time, the pups may increase their birth weight by a factor of four and increase their body fat from less than 5 per cent at birth to over 30 per cent by the time they are weaned."

The rapid weight gain allows pups to survive on their own once their mothers leave and they have to fend for themselves.

In a stroke of luck, the return of the seals to Scott Base coincides with the start of a new monitoring programme led by University of Canterbury student Shanelle Dyer and supported by Antarctica NZ.

The project makes use of the latest artificial intelligence methods to keep tabs on seals and other wildlife.