The Science of Arctic Melting
Ice caps | Melting and freezing | Greenhouse effect | Impact
In 2007 satellite images revealed that due to global warming the North-West Passage was, for the first time since records began, sufficiently ice-free for large ships to pass through the Arctic, although the route still remains hazardous.
Polar ice caps
Earth is not the only planet to have a polar ice caps. Many planets and moons have regions that are covered in ice at their ‘top’ and ‘bottom’. Mars’s ice caps are a combination of carbon dioxide and water ice. On Earth, our polar ice caps are made mainly of water ice and occupy about 7% of the area of the world’s oceans.
The melting and freezing cycle
Every year sea ice goes through a cycle of melting in the summer and freezing in the winter. Exploration of the Arctic is very much tied to this cycle. During the search for the North-West Passage the growth in sea-ice in the winter was responsible for blocking many routes and the necessity for ships to winter in the Arctic, their crews trapped along with their vessels by frozen seas for months at time. The crushing effects of this winter ice were one reason some ships did not return. The history of the search for the North-West Passage is full of accounts of voyages thwarted by the ice – either as a barrier to progress or as a wrecker of ships.
Global warming
In 2007 satellite images revealed that the passage was sufficiently free of ice for large ships to navigate, offering the possibility of the long sought-after trading shortcut between the Atlantic and Pacific oceans. However, even with this melting the passage remains hazardous.
What has caused the ice to melt so much? The answer is that the planet is warming. But why? The most likely answer to that question, according to the majority of climate scientists, is that human activity is heating up Planet Earth.
The Greenhouse effect
Certain gases in the Earth’s atmosphere absorb heat that rises from the surface – acting like a worldwide blanket. It’s useful that they do this. Without greenhouse gases the world would be considerably cooler (by 20–30°C) and much less hospitable. The most common greenhouse gases are carbon dioxide (CO2) and methane (CH4).
However, just as things can be less comfortable when we are too cold, so the same can be said when we get too hot. Since the Industrial Revolution of the 18th and 19th centuries human activity has been rapidly increasing the amount of greenhouse gases entering the atmosphere. Burning fossil fuels like coal and oil releases carbon dioxide. Cattle passing wind generate huge quantities of methane. At the same time many of the world’s forests, which play a vital role in absorbing greenhouse gases are being cut down to make way for agriculture. The predominant theory is that the ‘blanket’ around the planet is therefore getting ‘thicker’ as it accumulates more greenhouse gases - and this is what is causing the Earth to get hotter.
A hotter climate means that less ice forms in the Arctic during the winter, and ice melts quicker in the summer. Some recent predictions suggest that the Arctic may be completely free of ice in the summer by 2040.
Why is the ice melting so fast?
One theory that accounts for this incredibly rapid decline in ice is explained by the concept of ‘positive feedback’. Sea water absorbs heat from the sun, but ice (being white) reflects the sun rays back into space. As the ice decreases there is more sea water to absorb the heat and less ice to reflect it away, accelerating the overall warming process.
Another factor that may speed the melting is that the ‘meltwater’ appears to be pouring through holes in the ice far below, building up the lakes and rivers under the ice sheets, which then eases the slippage of vast chunks of ice into the sea.
Fossil fuels under the ice
Ironically, it is known that vast deposits of fossil fuels lie below the Arctic ice. These fossil fuels (the same as those which are believed to have contributed to global warming) will be easier to extract now the polar ice is melting – potentially leading to further global warming.
Emerging commercial possibilities such as these and a debate over which nation ‘owns’ the North-West Passage are already causing arguments between governments, notably those in Canada, the USA, Russia and Denmark. Find out more...
Impact
Arctic wildlife has naturally been deeply affected by the changes occurring in their habitats. For instance, the retreat of sea ice has reduced the opportunities for seals and walruses to rest between their searches for fish and mussels. Caribou (wild reindeer) now fall through ice that was once solid. Polar bears, who live on sea ice while hunting have found themselves with less time to feed and less access to the seals they prey upon.
For humans, melting permafrost (soil that stays at or below the freezing point of water) has destroyed the foundations of houses, eroded shorelines and forced people to move inland. Native Canadian Inuits, whose traditional way of life is inextricably linked to the ice, launched a human rights case against the American government. The USA’s production of greenhouse gases is a direct threat to their existence they say.
The melting of the Arctic will also have consequences worldwide, most obviously in rising sea levels that will threaten coastal communities.
Positive impact?
Ironically, the future opening up of the North-West Passage to shipping may offer one benefit to the environment. Commercial shipping is a major global contributor to CO2 emissions (more so than even aviation), so the shorter sea routes provided by the North-West Passage could significantly reduce emissions.
NB the International Chamber of Shipping are keen to point out that though the North-West Passage is now navigable, it is far from easy or safe to sail through. Read more...