At the southern pole is Antarctica. It is a continent covered with a sheet of ice and surrounded by ocean. During the winter, sea ice forms in the ocean around the continent, but nearly all of it melts during the summer months.
The continent of Antarctica is drier than the Sahara desert. It has an average snowfall of just 5 cm (2 in.) per year. Temperatures are so cold, the snow rarely melts. Over thousands of years, this snow accumulation has produced the largest ice sheet on the planet.
Zooplankton called krill are an important part of the food chain in oceans around Antarctica. Krill are shrimp-like animals that are very high in protein. They are small, but make a healthy meal for carnivores that inhabit these waters around Antarctica. Krill eat phytoplankton nourished by nutrients brought up from the deep by currents. Most animals on Antarctica come from the sea and are only temporary visitors to the land. The extreme cold and dryness on the continent limits plant growth.
Global warming of the planet and the atmosphere is of greatest concern at the poles. Ice is white and reflects sunlight energy. When ice melts, the darker colors of the ocean and land absorb sunlight energy instead of reflecting it. That makes Earth even warmer and puts the planet in a dangerous feedback loop. The warmer the planet, the faster the ice melts. Ice is frozen fresh water. When it melts, the fresh water that enters the ocean reduces the salinity, or saltiness. A change in the salinity of seawater affects ocean currents around the world. These currents affect global climate. Melting ice from land masses like Greenland or Antarctica would add huge volumes of water to the ocean. This may cause serious coastal flooding around the planet.
Satellite images show that most glaciers and ice masses are getting smaller. Large chunks of ice, some measuring several thousand square kilometers, are breaking off the ice sheet, drifting away, and eventually melting into the sea. Rising temperatures influence the ecological balance of not only the polar regions, but the entire planet. Summers are longer, winters are shorter. Seasonal changes can interfere with migration, hibernation, feeding, and mating patterns of animals. Climatic changes will affect vegetation and the availability of fresh water. Global warming may be the most significant ecological challenge in human history.
Penguin Facts
Penguins are birds that cannot fly. They lay eggs, breathe air with lungs, have feathers, and are warmblooded. All 17 species of penguins live in the southern hemisphere. Their torpedo-shaped body makes them fast swimmers. Penguins "fly" under water. They use their wing-like flippers to reach speeds of up to 15km/h (9 mph), then glide with their wings outstretched like other birds fly. While each species differs, most dives are within 21m (70ft) of the surface, and last less than a minute. However, emperor penguins have been observed diving as deep as 535 m (1755 ft), and remain submerged for over 21 minutes. When they surface, they often leap out of the water and breath through nostrils on their beaks.
Penguins spend up to 75% of their lives in the open ocean hunting krill, small fish, and squid. Layers of fat and soft down under stiff, overlapping outer feathers insulate them from temperatures that can get down to –45°C (–49°F). On land, penguins conserve body heat by tucking in their extremities and standing on their heels and tail. One way penguins conserve energy is tobogganing. Sliding on their bellies is more efficient and faster than walking. Some penguins keep their eggs from freezing by balancing them on top of their feet and covering them with their warm bodies.
Penguins are prey to sharks, seals, and killer whales. On land, penguin chicks are hunted by predatory birds.