• The land-based ice sheets of Greenland and Antarctica hold enough water to raise global sea level by more than 200 feet
• Three ice sheets (Greenland, Western Antarctica, Eastern Antarctica) hold 99% of the ice that would raise sea levels if global warming caused it to melt or go afloat (the remaining 1 % is locked up in mountain glaciers)
• Water under ice, no matter how it gets there, can lubricate the contact between bedrock and the bottom of an ice sheet. In Greenland for example, the warming Arctic climate has led to melt water on the surface that gushes into crevasses and drains to the base of the ice sheet. The drainage is closely linked to the acceleration of movement of ice towards the ocean.

Fore more information on ice sheets check out:

• Charles R. Bentley, Robert H. Thomas and Isabella Velicogna. Ice Sheets.

Can you imagine relaxing on a ship in coastal waters with calm weather or only light winds and then being hit unexpectedly by hurricane force winds?It would be quite a surprise!Certain coastal areas in Antarctica can be calm for much of the time until hit by a katabatic wind.Before slamming into your ship, the air in that katabatic wind was at a higher elevation on the slope of a tall mountain or a high glacial valley.As that air cooled, it became denser than the air below it and began to “flow” down the mountain towards your unsuspecting vessel.For that reason katabatic winds are sometimes called down slope wind orfall winds.How strong can these winds be?Douglas Mawson, a famous Australian explorer, recorded frequent gusts of more than 150 miles per hour (240 kph) at his Cape Denison base in 1912.

If you’re thinking about exploring Antarctica, however, the occasional katabatic winds aren’t the only winds that should concern you.Antarctica is the windiest of the continents and some coastal areas endure almost constant strong winds.Over the two years Mawson spent recording wind speeds at Cape Denison, the average wind speed was 45 mph (72 kph).

Why is Antarctica so windy?In addition to global wind currents, Antarctica creates its own wind systems.Cold air slides down the ice plateau, gaining speed as it leaves the high interior ice fields and descends to the lower areas near the coasts.These winds can form impressive clouds of blowing snow that reach high into the air.Winds this strong, combined with cold temperatures, would quickly freeze any human’s exposed skin.

Visualize a mountain range that is more than 800 miles (1300 km) long and 9,900 feet (3,000 meters) high. That’s twice as long as California’s Sierra Nevada and eight times higher than the Empire State Building. Now imagine it completely covered by an ice plateau—you could walk right over the top of this mountain range without even knowing it was there! You would need a lot of ice to cover a mountain range that big. This isn’t just an imaginary mountain range, however, it exists in Antarctica and is covered completely with ice. There are also several other massive mountain ranges in Antarctica with only isolated peaks and rock cliffs poking out from the ice dome that covers most of Antarctica. In some places in Antarctica the ice is more than 13,200 ft (4,000 meters) thick. That’s two and a half miles deep, or more than ten and a half times taller than the Empire State Building.

How much ice is on Antarctica? The Antarctic Ice Cap contains about 85% of the world’s ice, which is about 80% of all the fresh water on earth. That ice weights about 27 million billion tons (24,500 million billion kg). It’s difficult to conceptualize a number that large. It might help to imagine 100,000 tons, the weight that could be carried by a container ship 335 meters long and 43 meters wide, one of the largest cargo ships on the ocean. If you loaded all the ice on Antarctica onto these cargo ships and then starting counting the ships, assuming you could count one ship per second, you would still be counting more than 860 years from now. The massive weight of the ice cap pushes the underlying continent about 3,300 feet (1,000 meters) into the earth’s crust.

If someone asked you to name the world’s driest continent, what would you guess? Would you be surprised to know it is Antarctica? Even though most of Antarctica is covered with ice and snow holding eighty percent of the world’s fresh water, the continent is, by definition, a desert. Antarctica accumulates on average fewer than 2 inches (5 cm) of water equivalent per year—that is just slightly more than what the Sahara Desert receives. You might wonder how, if Antarctica receives such a small amount of precipitation each year, it could accumulate eighty percent of the world’s fresh water. The snow and ice that forms the Antarctic Ice Cap accumulated over millions of years.

Imagine what it would be like if your house or apartment grew and shrank every year. In the Antarctic winter, sea ice more than doubles the surface area of Antarctica, giving expanded habitat for animals like penguins, seals, and seabirds. The winter sea ice can extend over 7.2 million square miles (19 million square kilometers) of ocean surrounding Antarctica, that’s an area of sea ice more than two times the size of the United States. In the Antarctic summer, much of the sea ice disappears and then reforms the next winter.

Animals who live on the sea ice and humans who travel across and through it must be able to “read” the changing ice and choose safe places to travel and rest. As surface water cools to the freezing point, ice crystals start to form. If the weather and sea conditions are calm, the ice crystals join together and thicken into young ice, a fibrous and weak ice you would want to try to avoid if you were out for a walk. Even a slight ocean swell can break the young ice into pieces that knock against each other, forming flat circular slabs of thin ice that look like pancakes and are called pancake ice. If it’s cold enough the pancakes will eventually freeze together and then freeze fast to the shore, forming fast ice.

Animals like penguins, seals, whales, and sea birds rely on waves, wind, tides and currents to buckle and crack the fast ice to allow access between the ocean water and the ice surface and to create breathing holes. Humans traveling across the sea ice try to avoid these leads of open water.

During normal summers, the fast ice breaks apart and forms floes, pieces of ice anywhere from 65 feet (20 meters) to 6 miles (10 km) across. The floes drift on the currents until they pack tightly together forming pack ice. Modern ice breaking ships can move through sea ice, but pack ice gave early explorers a lot of trouble—in 1915 Ernest Shackleton’s wooden ship The Endurance was trapped when the pack ice closed around it, holding it for ten months before crushing it as the spring thaw allowed giant floes to grind the ship between them.

Antarctica has no native people and was officially “discovered” only 188 years ago. There is no agreement about which of three sailors first saw the continent; a Russian, a Brit or an American. It is also possible that any of a number of people aboard the numerous sealing boats sailing greater and greater distances south in search of dwindling seal populations could have been the first to see Antarctica.

Great Britain, New Zealand, France, Norway, Australia, Chile, and Argentina all made claims to parts of the continent.

Other countries, however, would not recognize those claims. Until the middle of the 20^th century, Antarctica was a virtual “free-for-all” as ships from many nations hunted fur seals, elephant seals, and whales until the populations of these sea mammals collapsed.

In 1946 the International Whaling Convention formed to try to conserve the populations of whales. Fifteen years later, twelve countries including the Soviet Union, the United States, the United Kingdom, and Argentina signed the Antarctic Treaty. The Antarctic Treaty suspends all claims to Antarctica and designates the continent as a scientific preserve. The treaty also bans any nuclear explosions, dumping of nuclear waste, or military activity on the continent.

In 1991 the Protocol on Environmental Protection was added to the Antarctic Treaty. The protocol aims to further protect the Antarctic environment. Among other measures, the protocol forbids any non-native species (besides humans) to be brought to Antarctica. Even sled dogs had to be removed from Antarctica. The end of the Antarctic sled dog tradition saddened some people, but most took comfort from the protocol’s strong message of the need to protect the Antarctic environment and ecosystems.

Sources:

Ritchie, T. (2007) The Antarctica Primer, 2^nd edition. Lindblad Expeditions, New York.

Antarctic Sea Ice Processes and Climate, http://www.aspect.aq/ www.wikipedia.org

In 1991 Will Steger’s international team of explorers spent weeks crossing the Larsen ice shelf on the eastern side of the Antarctic Peninsula. The team’s photographs from the Larsen show a flat plain of snow-covered ice extending to the horizon, similar to images from the salt flats. You would guess, looking at the photographs, the team members, their sleds and dogs were standing on solid ground. Below their feet, however, was approximately 720 feet (220 meters) of ice floating on top of the ocean.

How do shelves of ice form? As you might imagine, it’s a long process. First a cold spring season allows fast ice, a layer of sea ice that is frozen fast to the shore, to remain in place through the next year. Fast ice that survives more than one year is called bay ice. Bay ice that stays in place for many years is called shelf ice. Shelf ice gets thicker not only from freezing seawater, but also from snow and from glaciers moving towards the coasts. Ice shelves can be up to 1000 ft (300 m) thick. That’s almost a fifth of a mile thick.

While crossing the Larsen, the ice shelf felt very stable to Steger and his team. Scientists at Queen’s University estimate the shelf could have been stable for as long as 12,000 years—that many years ago there were still mastodons, mammoths, and saber-toothed cats roaming the earth. Over the course of three days in 2002, however, a chunk of ice the size of the New England state of Rhode Island broke free from the Larsen B ice shelf. The speed of the collapse surprised even the scientists who were monitoring the shelf. Scientists link the collapse with global climate change.

Apsley Cherry-Garrard wrote a book called The Worst Journey in the World to tell the story of Robert Scott’s early Antarctic explorers, but the title could have described any number of early attempts to explore the coldest, windiest, driest, highest, and most remote continent on earth. Early explorers suffered from scurvy, frostbite, hypothermia, starvation, and snow blindness. They fell through crevasses, plunged through thin ice, were chased by leopard seals, had their ships stuck in pack ice and crushed, were stranded on remote spits of inhospitable beaches, and had other misadventures. Antarctic exploration produced some of the most spectacular stories ever told of human endurance and desperate survival.

Does this sound like a place you would like to go on vacation? Would you believe for more and more people every year, Antarctica is their holiday destination of choice? Over 37,500 tourists visited in 2006-2007 and 80,000 a year are expected by the year 2010. Most visitors come on tour ships, but some also fly on commercial airplanes.

A visit to Antarctica has become far more safe and comfortable than it was for the early explorers, but travel to the southern continent still has its hazards. In 1979 an Air New Zealand sightseeing flight crashed into the side of Antarctica’s Mount Erebus, killing all 257 people aboard. In November 2007 the passenger cruise ship Explorer struck an ice berg of the coast of Antarctica’s Shetland Islands and sank. Luckily the 150 passengers and crew were rescued by a Norwegian ship and no one was killed.

Tourism to Antarctica also poses hazards to the fragile Antarctic ecosystem and environment. Some scientists and environmentalists have called for quotas on numbers of visitors and tighter regulations on ships.

Imagine you are tiny bacteria or a bit of algae whose job it is to colonize the gravel, sand, clay and silt left over after rocks break apart. The life you produce in the mineral soil will make an inviting home for higher-order plants that will colonize the new soil, eventually building an organic soil that is a nurturing home for familiar plants like ferns, bushes and trees.

Now imagine that you’ve only just started colonizing a fresh patch of sand when a bunch of new sand lands on top of you, burying your work. You start again, but the wind blows you away. You try a different place, but a stream of melt-water washes you away. You try again, but the temperature is just too cold. You might start to appreciate why much of the soil in Antarctica is poor. The soils on inland peaks in Antarctica are virtually sterile (lifeless) and the soil in some of the dry coastal areas hosts only the most simple microscopic organisms. The only richly organic soils to be found on Antarctica are in penguin colonies where the penguin droppings mix with the soil.

Consider the lack of good soil along with the extreme climate and you can start to understand why Antarctica doesn’t have very many plants. Antarctica has only 400 species of lichens (for comparison, the state of California has over 1,500 species of lichen), 75 species of mosses, one species of grass, no ferns, no bushes and no trees. The plants that do manage to grow in Antarctica grow very slowly. Only a few species grow taller than 1.25 inches (3 cm).

In May of the year 2000 a chunk of ice measuring 4,250 square miles (11,000 square kilometers) broke free from Antarctica’s Ross Ice Shelf. The size of the New England state of Connecticut, this tabular berg, which is flat unlike the jagged and pointy icebergs that break off glaciers, was the largest floating thing on earth.

You may wonder what impact a berg that size can have on the animals that live near it. In 2002 and 2003 and again in 2005 the gigantic berg broke into smaller pieces, forming a dam that kept the pack ice from following its normal summer path out to the open sea.

Phytoplankton, the primary food of krill, which are in turn food for the rest of the Antarctic food web, need open water and light to reproduce. The ice dam and all the pack ice caught behind it blocked out the light and caused a 40% decline in plankton. Less plankton meant fewer krill, which meant less food for penguins. Not only did penguins have less food, they had to swim further to get it as they had to swim around this massive iceberg.

What would you do if your home grocery stores suddenly had not enough food? Might you consider moving? Some penguins made that choice and abandoned their rookeries.

Source:

Shwartz, M. (2002). Satellite imagery shows how icebergs affect Antarctica’s food chain, Stanford Report, April 24.

It’s like something out of a science-fiction horror movie: creatures that feed on slime coating the underside of sea ice, and swim in swarms of as many as 35,000 per square meter, advancing in a narrow band or sheet. They eat by gathering food between their legs and stuffing it in a sort of sausage casing while they digest it. If they run low on food, adults can “develop in reverse”, losing their sex organs and regressing through previous life stages to a more immature life form that can absorb nutrients directly from the water.

These creatures may seem like science fiction, but they exist; they are krill, crustaceans that somewhat resemble shrimp. Krill are the primary food for Antarctic fish, squids, penguins, albatrosses, petrels, whales, and some seals. Penguins eat so much krill that their droppings are stained bright red by the krill’s red pigments. Blue whales can eat up to 5 tons (4,500 kg) of krill in one day. One of the largest species of krill in the world weighs just over 1 gram as an adult, so that means one blue whale can eat about 4.5 million individual krill a day—that is more than the human populations of Philadelphia, Phoenix and San Antonio combined! Baleen whales eat so much krill they can increase their body weight by 50% during the summer months they spend feeding in Antarctic waters.

Because virtually all of the animals in Antarctica rely either directly or indirectly on krill, krill are called a keystone species. In construction, a keystone is the stone at the summit of an arch that locks the whole structure together. Without the keystone, the arch would fall. The same idea holds true for the krill as a keystone species; without krill the entire Antarctic ecosystem would collapse.

Krill depend on the slime coating on the underside of sea ice to survive through the Antarctic winters. Over the last twenty years the extent of winter sea ice has decreased, greatly reducing the krill populations.

Have you ever seen footage of penguins walking around in the cold wind and wondered why they seem so comfortable in temperatures that would quickly freeze human skin? Would you believe penguins are so well adapted to life in cold places they have a more difficult time dealing with warm temperatures than they do with cold?

How do penguins stay warm? Other birds grow feathers only in narrow tracts and then fluff them out to cover the rest of their bodies. Penguins, in contrast, have dense, scale-like feathers with downy tufted bases tightly covering their entire body. Underneath the many feathers, penguins also have a thick layer of fat that insulates them from the cold. Even though they live outside in extreme cold, the 101°F (38°C) internal body temperature of a penguin is higher than the average human body temperature.

Imagine yourself wearing several thick sweaters, a couple pairs of sweatpants, a wool hat, mittens, and a big puffy coat with the hood cinched down tightly. Now think about walking into a heated room and you might start to have some idea what it must be like to be a penguin in warm temperatures. What would you do if you started to overheat? Penguins can’t take off their coats, but they can try to lose heat through their feet, the only part of their bodies not covered in feathers. Penguins have many blood vessels in their feet and can send warm blood out into their feet to cool it down before it is pumped back into their body core. Before penguins dive into the cold water they can squeeze the blood out of their feet to keep from losing too much heat to the water. This explains why the feet of penguins that just jumped out of the water are white, but the feet of penguins nesting on land can be rosy.

Not only do penguins rely on cold temperatures to stay comfortable; they also rely on cold to maintain the sea ice they use for hunting, resting and, for the Emperor Penguin, making colonies for raising young.

Which of the world’s oceans would you guess is the most biologically productive? Would you guess a tropical ocean? Would you be surprised to find out it is the Antarctic Ocean? The water surrounding Antarctica accounts for only five percent of the world’s sea water, but produces twenty percent of the world’s sea life (measured by weight). Antarctic waters yield six times more life per square meter of surface area than the average yield of the other oceans.

What makes the Antarctic Ocean so rich with life? There are three reasons: long hours of daylight in the Antarctic summer to help algae grow, turbulent waters that keep nutrients floating in the water where phytoplankton can reach them, and the very cold water.

Why is cold water more productive? Cold water can hold more dissolved oxygen than warm water. The levels of dissolved oxygen in Antarctic waters are so high that many fish have few or no red blood cells (the blood cells other animals, including humans, use to carry oxygen). Without red blood, the fish appear white or nearly colorless.

The high levels of dissolved oxygen in Antarctic waters allow as many as 35,000 krill (small crustaceans that look a little like shrimp) to swarm in one cubic meter of sea water. These high numbers of krill support the rest of the Antarctic food web, providing food either directly or indirectly for virtually all the other animals in Antarctica.

Arctic (North):

• A vast ocean surrounded by land inhabited by people for thousands of years. Home to four-million current human residents.
• Includes parts of the United States, Canada, Russia, Norway, Sweden, Finland, Greenland (Denmark), and Iceland.
• Home to polar bears, wolves, foxes, caribou, lemmings, wolverines, muskoxen, and other land mammals.
• Summer home for several hundred million birds that migrate there to feed and breed. The Arctic, however, has no flightless birds. That’s right; there are no penguins in the Arctic!
• The top layer of permafrost soil thaws every summer, giving rise to flowering plants, berries, and insects. Some Arctic areas even have trees.

Climate Change concerns

Melting permafrost can release large amounts of carbon into the atmosphere; reduced sea ice cover will reflect less incoming solar radiation, letting the dark underlying ocean waters absorb more heat; changes in ocean water salinity, temperature and ice cover could disrupt global ocean circulation; melting ice sheets and glaciers contribute to global sea-level rise.

Antarctica (South):

• A vast continent surrounded by ocean.
• No evidence of prehistoric human populations.Not “discovered” until 1820s. No permanent human residents.
• Owned by no nation. Forty-six nations have signed the Antarctic Treaty, setting Antarctica aside as a scientific preserve and banning military activity on the continent.
• No land mammals. That’s right; there are no polar bears in Antarctica!
• Millions of sea birds feed and breed during the Antarctic summer. The birds that call Antarctica home are all sea birds, however, because in contrast to the Arctic, there is no tundra and few insects to feed and house non-sea birds.
• The Antarctic continent is mostly ice-covered rock. There is very little fertile soil, only a few species of plants that grow only along the coast of the peninsula, and not many insects. There are no shrubs or trees.

Climate Change concerns

Ice sheets and glaciers in Western Antarctica and on the Antarctic Peninsula could slip into the ocean, causing a global sea-level rise of up to eighty feet. Cold water and ocean currents make Antarctic waters the most biologically productive in the world, providing food that sustains the world’s ocean life. Changes in sea temperature, currents and ice cover could decrease the richness of Antarctic waters.