Possession Islands, Antarctica | Ross Sea History & Wildlife

The Possession Islands are not a single island, but a tight cluster of small islands, islets, and rocks scattered across the western Ross Sea, just offshore from Victoria Land. Dark volcanic cliffs rise straight from the water, and in early summer the sea ice fractures into lanes and floes—one of the starkest front-porch views of the Ross Sea coast.

An archipelago of basalt and weather

Seen up close, the Possession Islands read like a study in contrasts: black rock and white ice, sharp ridge-lines and flat, wind-scoured benches, calm water and sudden swell. Their volcanic geology shows in the blocky cliffs and rubble slopes—terrain that looks austere from offshore, but becomes textured and surprisingly detailed once you are near the landing beaches and low terraces.

Wildlife: a Ross Sea stronghold for Adélies and skuas

For such a small island, Possession Island is a major wildlife stronghold. Long-term monitoring counts an average of over 100.000 breeding pairs of Adélie penguins and records around 500 breeding pairs of South Polar skuas.

Up close, it means a living hillside—penguin traffic, skuas on patrol, and feeding waters offshore—so even in a stark landscape, the place feels unmistakably alive.

The 'message post' era: Antarctica’s earliest mailbox

One of the most fascinating human stories at the Possession Islands came after the first flag was raised. Before radio, Antarctic expeditions relied on message posts—simple markers where crews could leave notes for ships that might come after them.

The first message post here was set up in January 1895 by a landing party from the Norwegian whaling ship Antarctic, led by Captain Leonard Kristensen. The post was modest: a wooden pole supported by rocks, with a small metal box attached. Inside was a written note recording the landing and the ship’s presence.

Its purpose was practical rather than ceremonial. If a relief ship arrived later, it could check the post to learn who had been there, when, and where they planned to go next—a vital safety system in a place where ships could vanish for years without word.

The Possession Island message post remained in use for only a short time. It was visited, opened, and updated during later expeditions between 1895 and 1903, after which radio communication made such posts unnecessary. Even so, it left an enduring mark: researchers now describe it as the earliest known human-built structure in the Ross Sea sector south of the Antarctic Circle.

There has been long-standing confusion over its exact location, partly due to the close proximity of Possession Island and nearby Svend Foyn Island. For readers interested in the archaeological and historical detective work behind this, please read further in the Canterbury Museum Records.

Visiting today: rare, ice-dependent, and often offshore-only

The Possession Islands are not a routine landing site. Even in summer, heavy sea ice and swell can keep ships at a distance, turning the visit into an offshore viewing opportunity rather than a shore programme. When conditions do align—most often in the late-summer window—the experience tends to be about proximity: reading the cliffs, watching penguin highways from a respectful distance, and appreciating how quickly the Ross Sea can close again.

Header Photo Credit: Eugene Kuo