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Earth from Space – Frozen fields of Antarctica

EO-1 image of ice in Antarctica

Satellite image of fields of ice on the Antarctic coast.

THOUGH IT IS ALL COMPOSED of frozen water, ice is hardly uniform. On October 7, 2011, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this image of a variety of ice types off the coast of East Antarctica.

Brilliant white ice fills the right half of this image. It is fast ice, and derives its name from the fact that it holds fast to the shore. This ice is thick enough to completely hide the underlying seawater, hence its brilliant white colour.

Trapped within the fast ice, and stuck along the edge of it, are icebergs. Icebergs form by calving off ice shelves—thick slabs of ice attached to the coast. Ice shelves can range in thickness from tens to hundreds of metres, and the icebergs that calve off of them can tower over nearby sea ice. One iceberg, drenched with meltwater, has toppled and shattered (image upper right). The water-saturated ice leaves a blue tinge.

The icebergs along the edge of the fast ice are likely grounded on the shallow sea floor, and their presence may help hold the fast ice in place.

Farther out to sea is pack ice that drifts with winds and currents. Much thinner than the fast ice, the translucent pack ice appears in shades of blue-grey.

The pack ice includes some newly formed sea ice. As seawater starts to freeze, it forms tiny crystals known as frazil (image centre). Although the individual crystals are only millimetres across, enough of them assembled together are visible from space.

Constantly moved by ocean currents, frazil often appears in delicate swirls. Frazil crystals can coalesce into thin sheets of ice known as nilas (image top). Sheets of nilas often slide over each other, eventually merging into thicker layers of ice.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Michon Scott based on image interpretation by Ted Scambos, National Snow and Ice Data Centre.

Download the full-size (4MB) image here.

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Iceberg’s break from Matusevich Glacier

Matusevich Glacier iceberg calves

NASA's Earth Observing-1 (EO-1) satellite spotted large icebergs calving from the Matusevich Glacier in East Antarctica.

The Matusevich Glacier flows toward the coast of East Antarctica, pushing through a channel between the Lazarev Mountains and the northwestern tip of the Wilson Hills.

Constrained by surrounding rocks, the river of ice holds together. But stresses resulting from the glacier’s movement make deep crevasses, or cracks, in the ice.

After passing through the channel, the glacier has room to spread out as it floats on the ocean. The expanded area and the jostling of ocean waves prompts the ice to break apart, which it often does along existing crevasses.

See the full-size, high-resolution image here (will open in a new window or tab).

On September 6, 2010, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-colour image of the margin of Matusevich Glacier.

Shown here just past the rock-lined channel, the glacier is calving large icebergs. Low-angled sunlight illuminates north-facing surfaces and casts long shadows to the south. Fast ice anchored to the shore surrounds both the glacier tongue and the icebergs it has calved.

Compared to the glacier and icebergs, the fast ice is thinner with a smoother surface. Out to sea (image left), the sea ice is even thinner and moves with winds and currents.

Matusevich Glacier does not drain a significant amount of ice off the Antarctic continent, so the glacier’s advances and retreats lack global significance. Like other Antarctic glaciers, however, Matusevich helps glaciologists form a larger picture of Antarctica’s glacial health and ice sheet volume.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Text adapted from information issued by Michon Scott (NASA Earth Observatory) based on image interpretation by Robert Bindschadler, NASA Goddard Space Flight Centre, and Walt Meier, National Snow and Ice Data Centre.

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