Polar Regions - page 4
The Tip of the IcebergBecause icebergs and sea ice are both large fragments of ice floating in the ocean, it's easy to get them confused. The simplest way to remember the difference is that sea ice is made of sea water and icebergs are made of ice water.
Icebergs are fragments of ice that have broken off from large glaciers that flow into the ocean. Most icebergs form in Alaska, Greenland, and Antarctica. Up to 90% of an iceberg's total volume lies below the surface of the ocean, so the visible part of an iceberg may be a poor indication of its true size.
First-year sea ice drifts in the Ross Sea, Antarctica. A penguin toboggans in the foreground. (Image Credit: NOAA; Michael Van Woert, photographer)
Sea ice is a fragile layer of frozen ocean water that forms in polar oceans. It forms a boundary between the cool atmosphere and the warmer ocean water. Because water is less dense as a solid (ice) than as a liquid, sea ice floats on top of the ocean. In recent years, measurements of seasonal sea ice extent on Earth have provided clues about warming trends and changing global climate.
Life at the Ends of the Earth
Emperor penguins march across the Southwest Ross Sea, Antarctica. (Image Credit: NOAA; Michael Van Woert, photographer)
Penguins, on the other hand, live only in the Southern Hemisphere between 40° and 60° South. Most live along Antarctic coastlines and on sub-Antarctic islands, but some species are found as far north as the Galapagos Islands near the equator.
While Antarctica has no terrestrial mammals, the Arctic is home to caribou, musk ox, reindeer, wolves, bears, and other land-dwelling mammals. Seals, whales, and dolphins are found in both Arctic and Antarctic waters.
A polar bear stands on an ice floe in the Arctic. (Image Credit: Kathy Crane, NOAA Arctic Research Office)