Warming to Cause Catastrophic Rise in Sea Level?

There is little doubt that the Earth is heating up. In the last century the average temperature has climbed about 0.6 degrees Celsius (about 1 degree Fahrenheit) around the world. This may not sound like much, but even half a degree can have an effect on our planet.

From the melting of the ice cap on Mount Kilimanjaro, Africa’s tallest peak, to the loss of coral reefs as oceans become warmer, the effects of global warming are often clear.

However, the biggest danger, many experts warn, is that global warming will cause sea levels to rise dramatically. Thermal expansion has already raised the oceans 4 to 8 inches (10 to 20 centimeters). But that’s nothing compared to what would happen if, for example Greenland’s massive ice sheet were to melt.

According to the U.S, Environmental Protection Agency (EPA) the sea level has risen 6 to 8 inches (15 to 20 cm) in the last 100 years. This higher temperature may be causing some floating icebergs to melt, but this will not make the oceans rise. In order to float, the iceberg displaces a volume of water that has a weight equal to that of the iceberg. Icebergs are chunks of frozen glaciers that break off from landmasses and fall into the ocean. The rising temperature may be causing more icebergs to form by weakening the glaciers, causing more cracks and making ice more likely to break off. As soon as the ice falls into the ocean, the ocean rises a little.

Each year about 8 mm (0.3 inch) of water from the entire surface of the oceans goes into the Antarctica and Greenland ice sheets as snowfall. If no ice returned to the oceans, sea level would drop 8 mm every year. Although approximately the same amount of water returns to the ocean in icebergs and from ice melting at the edges, scientists do not know which is greater — the ice going in or the ice coming out. The difference between the ice input and output is called the mass balance and is important because it causes changes in global sea level.

Antarctica and Greenland, the world’s largest ice sheets, make up the vast majority of the Earth’s ice. If small glaciers and polar ice caps on the margins of Greenland and the Antarctic Peninsula melt, the projected rise in sea level will be around 0.5 m.

The main ice covered landmass is Antarctica at the South Pole, with about 90% of the world’s ice and 70% of its fresh water. It is covered with ice an average of 2,133 meters (7,000 feet) thick. If all of the Antarctica ice melted, sea levels around the world would rise about 61.1 meters.

The complete melting of Greenland would raise sea levels by 7.2 meters, contributing about 30% of all glaciers melt to rising sea level. But even a partial meeting would cause a one-meter (three-foot) rise. Such a rise would have a devastating impact on low-lying island countries, such as the Indian Ocean’s Maldives, which would be entirely submerged.

Densely populated areas like the Nile Delta and parts of Bangladesh would become uninhabitable, potentially driving hundreds of millions of people from their land.

A one-meter sea level rise would wreak particular havoc on the Gulf Coast and eastern seaboard of the United States. A 6-meter (20 foot) sea level rise would submerge a large part of Florida.

Most scientists believe the rise in temperature will in fact accelerate in a faster rate. The United Nations-sponsored Intergovernmental Panel on Climate Change reported in 2001 that the average temperature is likely to increase by between 1.5 and 5.8 degree Celsius (2.5 and 10.4 degree Fahrenheit) by the year 2100. With the current acceleration of glacier contribution to sea level rise, the total contribution from small glaciers and ice caps by the year 2100 is expected to be 240 +/- 128 millimeters, which represents an average annual increase of more than 2.0 millimeters per year. ”With sea level rise, there’s really no technological way to put the ice back on Greenland,” said Marianne Douglas, a geology professor at the University of Toronto.

copyrighted © National Geographic News, NSIDC, Marshall Brain :: Image by © Robert A. Rohde :: Video © The Inconvenient Truth

Arctic Summers Ice-free

A new Nasa-led study found a 23% loss in the extent of the Arctic's thick, year round sea ice cover during the past two winters. This drastic reduction of perennial winter sea ice is the primary cause of this summer's fastest-ever sea ice retreat on record and subsequent smallest-ever extent of total Arctic coverage.

From the 1970s through the 1990s, prennial ice declined by about 500,000 square kilometers (193,000 squares miles) each decade. Since 2000, that amount of decline has nearly tripled. Between winter 2005 and winter 2007, the perennial ice shrunk by an area the size of Texas and California combined.

The minimum ice extent reached in September 2007 shattered the previous record for ice withdrawal set in 2005, of 5.32 milliion square km.

The long-term average minimum, based on data from 1979 to 2000, is 6.74 million square km.

In comparison, 2007 was lower by 2.61 million square km, an area approximately equal to the size of Alaska and Texas combied or the size of 10 United Kingdoms.

The Arctic saw another milestone in the summer of 2007. The ice cap shrank so much this summer that waves briefly lapped among two long-imagined Arctic shipping routes, the Northwest Passage over Canada and the Northern Sea Route over Russia. In August 2007, the Northwest Passage had almost no floating ice. It was the first time the Passage had been completely open to shipping since people started keeping records in 1972. Scientists say that the lack of ice represents clear proof that the planet is warming.

Experts say the ice retreat is likely to be ecen bigger next summer because this winter's freeze is starting from such a huge ice deficit. Professor Maslowski's group, which includes co-workers at Nasa and the Institute of Oceanology, Polish Academy of Science (PAS), is well known for producing modelled dates that are in advance of other teams. He projects a blue Arctic Ocean in summers by 2013. "In the end, it will just melt away quite suddenly. It might not be as early as 2013 but it will be soon, much earlier than 2040." Other teams have variously produced dates for an open summer ocean that, broadly speaking, go about 2040 to 2100.

Discussing the possibly for an open Arctic ocean in summer months, he told the meeting: "A few years ago even I was thinking 2050, 2070, out beyond the year 2100, because that's what our models were telling us. But as we've seen, the models aren't fast enough right now; we are losing ice at a much more rapid rate."

Ice re-forms during winter, but due to warmer waters the amount of re-formed ice appears to be decreasing. Ice that was previously considered "permanent" is now melting. That leaves an ever-decreasing base of ice at the beginning of each melting season.

Sea ice plays an important role in keeping temperatures down around the world. Whereas sea ice reflects 80% of sunlight back into the atmosphere, ocean water absorbs 90 percent of sunlight. As melting ice exposes more ocean to direct sunlight, scientists expect water temperatures to rise, accelerating the ice melt.

This record pace of Arctic ice melt has scientists concerned about rising sea levels, diminished habitats for polar bears and other animals and an impending rush for fossil fuels in the region. Increased traffic through the Northwest Passage and the Northeast Passage (which runs by Siberia) may increase pollution in the area. Experts estimate that 25% of the world's remaining fossil fuel reserves lies under the Arctic seabed. Commentator Jeremy Rifkin noted with irony that it's the burning of fossil fuels and the subsequent rise of global temperature that has made it possible to access these long-blocked stores of oil and gas.

Scientist call this rush for fossil fuels and the melting of permafrost in Siberia and other areas a "ticking time bomb". If Siberia's vast permafrost continues to melt, massive amout of methane, now trapped beneath the ice, may be released. Methane is a highly potent greenhouse gas, more than 2o times stronger than carbon dioxide. Scientists fear that the release of so much methane may initiate a sort of feedback loop, wherein methane release increase the rate of global warming. In turn spurring more permafrost melt and more methane release.

One of the most visible effects of Arctic ice melt is the calving of large pieces of ice from glaciers and ice shelves. In 2005, the Ayles Ice Island, a 30-square mile chuck of ice broke away from Canada's Ayles Ice Shelf and began drifting through the Arctic.

The faster the Arctic melts and the closer our planet comes to catastrophic climate change. "The Arctic may have another ace up her sleeve to help the ice grow back," Dr. Eicken said. "But from all we can tell right now, the means for that are quite limited."

Melting Artic Ice

Artic Ice Abrupt Withdrawl - Present - 2040

copyrighted © Andrew C Revkin (The New York Times), Jacob Silverman, Jonathan Amos (BBC News), NASA

Are Polar Bears Endangered?

Polar bears and other Arctic species are particularly at risk because their habitat is increasingly threatened by global warming.Over the past three decades, more than a million square miles of sea ice -- an area the size of Norway, Denmark and Sweden combined -- have disappeared. Scientists predict that 80 percent of the summer sea ice that polar bears depend on for survival could be gone in 20 years, and all of it by 2040. As a result, the world's polar bears could face global extinction by the end of this century.

The polar bear has been reclassifed as vulnerable on the IUCN World Conservation Union's "Red List of Threatened Species," noting that the species could become extinct due to sea ice changes. Already, more than 25 percent of the world's polar bear populations are in decline.

Polar bears spend most of their summers roaming the Arctic on large chunks of floating ice. They drift for hundreds of miles, finding mates, hunting for seals and fattening themselves up for the winter. Without these thick rafts of sea ice, the world's largest bear could not survive. Yet at this moment, the polar bear's Arctic habitat is literally melting away beneath it due to global warming.

Pack ice overall is decreasing globally. When pack ice does form, it melts more quickly, and tends to be thinner as well. In 2004, several polar bear deaths by drowning were recorded, something which was hitherto unheard of. The polar bears had been trapped on isolated areas of floating ice, and had tried to swim for land. Due to the shrinkage of the ice, the polar bears tired and drowned before reaching shore and safety. This problem will only grow as the pack ice shrinks.

The shrinkage of the ice has other repercussions for polar bears. They are losing their natural prey, who are also affected by the shrinkage in habitat. Polar bears are not very adept at catching land animals. Land animals also do not provide the high fat diet that polar bears need, which will lead to starvation. Starving mothers will not be able to provide their cubs with the nutrition they need, which will further contribute to the decline in polar bear numbers.

While searching for food and habitat, polar bears have also clashed with humans. Interactions with polar bears used to be very rare, because the bears kept to the sea ice. With the disappearance of the sea ice, polar bears have begun to show up around inhabited areas looking for food and shelter. They contend with hunters for their kills and often end up being slaughtered because they pose a threat to human communities.

Evidence of the dire impact of global warming on polar bears continues to mount. That evidence includes polar bear drownings, cannibalism, starvation, reduced cub survival and denning dislocation.

• Polar bears are one of the world's strongest swimmers but four were found drowned in the Bering Strait. Scientists believe that as many as 27 may have perished.


• Two female polar bears were found starved to death, without any fat stores.


• Newborn cubs were crushed to death when their snowy dens collapsed from unseasonable rains


• A majority of pregnant polar bears in Alaska are now digging snow dens on land rather than on sea ice.

The combination of deadly factors brought about by global warming put polar bears at a very high rate of risk. Drops in birth and survival rates have already been documented, and biologists are growing concerned about erratic behavior exhibited by polar bears as a result of the loss of their natural habitat. Organizations dedicated to the welfare of the environment believe that a global effort is needed to counteract global warming before it is too late for polar bears, as well as many other species that call Earth home.

copyrighted © PBI , wiseGeek , BIOGEMs :: Image by © Richard Wear/Design Pics/Corbis :: Video © The Inconvenient Truth

Animation: Greenhouse Effect

Without the natural greenhouse effect, the Earth would have had an average temperature around - 19 °C.

Animation: Global Warming

Human emissions of greenhouse gasses amplifies the natural greenhouse effect which increases global temperatures.

Animation: Impacts on the Arctic

The impacts of global warming will be particularly dramatic for the Arctic and Antarctica. In this animation, we will look more closely at the consequences for the Arctic.