Polar Regions - page 4
The Tip of the Iceberg
Because 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
Because the Arctic and Antarctica both have extremely cold environments, you might think that the same forms of life exist in both places. But the two poles each have some unique animals. For instance, polar bears are only found in the Arctic. Weighing up to 800 kg (1764 pounds), these meat-eating giants live along the coastal regions and islands of the Arctic seas. They spend most of their time on ice packs, but they can also swim long distances in icy cold waters.
Icebergs float near the Antarctic Peninsula. (Image Credit: NOAA; Richard Behn, photographer)
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.
Human population in Antarctica is sparse and restricted to a few scattered scientific stations. In addition, no record of primitive human cultures or native groups has been found there. In the Arctic, however, there are native ethnic groups and a long, cultural record of human settlement. Currently, about two million people live in modern settlements in the regions north of 60° North.
A polar bear stands on an ice floe in the Arctic. (Image Credit: Kathy Crane, NOAA Arctic Research Office)