The sea ice apron around Antarctica swells from 4 million square kilometers in summer to 19 million square kilometers in winter. This effectively doubles the size of Antarctica, a continent twice the size of Australia - every winter!

The summer of 2001/2002 was a good one for sea ice - in many places, it didn't melt. However, this caused devastating problems for nesting penguins. The penguins had to trek further from their nests to their fishing grounds and thus had less food for their chicks. From late January to early March 2002, most of the sea ice in the Antarctic Peninsula was confined to coastal areas along the Grandidier Channel and in and around Marguerite Bay.

Bergs and sea ice
Grandidier Channel

Icebergs in Antarctica carve off ice shelves and valley glaciers. Larger icebergs may become grounded in shallower areas, only moving when they have sufficiently melted. Icebergs drift in a clockwise pattern around Antarctica, pushed by the powerful Antarctic Circumpolar Current.

Pack ice and a hint of Antarctica
Beascochea Bay

Sea ice plays a vital part in the nature's regulation of our climate. Sea ice is a very effective insulator and decreases the amount of heat lost from relatively warm oceans (-1.9C) to the much colder atm (-30C). The white expanse of sea ice also reflects a lot of the solar radiation back into space, thus helping regulating temperatures on the Earth.

Sea ice at sunset
Grandidier Channel

The boundary between open sea and sea ice is usually quite sharp in summer, being defined by prevailing winds and currents pushing the sea ice fragments. The actual boundary is defined by several meters of brash ice (small sea ice fragments) giving way to larger fragments of sea ice up to several 10s of meters in size. The sea ice boundary can fluctuate up to 10km a day.

Broken sea ice
Marguerite Bay

Close to the continent, the broken sea ice floes are pushed close together forming pack ice. In Antarctica, the sea ice rarely exceeds 3m in thickness, in contrast to up to 7m thickness in the Arctic. Sea ice is thicker in the Arctic because the North Pole is a frozen ocean surrounded by land, so there is no where for the ice to go and it piles up. In contrast, Antarctica is a frozen land mass surrounded by ocean.

Ice breaking
Grandidier Channel

Pack ice density (i.e. how much space is between the pieces of ice floe) are a factor in ice breaking. With only 10% of the ocean covered in sea ice, an ice breaker can move with relative ease. However, when there is no space between the sea ice, it will take a long time to break through. In this example, the sea ice floes are not pushed together and we were able to sail through relatively quickly, pushing aside the sea ice floes.

Iceberg
Marguerite Bay

Freezing may continue for the entire winter season, generating first year ice which usually has a rough surface and thickness up to 1-2m. Ice that persists for a number of years is called multi-year ice, which maybe several metres thick. Due to weathering, the surface of multi-year ice floes tend to be smoother and the internal ice characteristics change; salt leaches out and brine inclusions form. Both first and multi-year forms floes under the action of wind, waves and tides. First year ice floes tend to be more uniform with jagged edges. Multi-year floes are often crazed with re-frozen linear cracks and are rounded through continuous grinding against other fragments of sea ice.