Melting Arctic Sea Ice

Here is a link to a video from The Economist showing how Arctic sea ice has changed since 1979. The economic implications of this melting sea ice is that it will soon be possible for large cargo ships to cross the Arctic ocean. This should make it easier and cheaper to ship cargo between the Atlantic and Pacific oceans.

The environmental implications are more complicated. Less Arctic sea ice means less sunlight being reflected and more heat being absorbed by the Arctic ocean. This will intensify the warming process. One big concern is what effect this warming will have on the large deposits of methane hydrate that are in the Arctic.

The October 2011 issue of National Geographic has a story titled Hothouse Earth, which describes a time  when

"56 million years ago a mysterious surge of carbon into the atmosphere sent global temperatures soaring."


During the Paleocene-Eocene Thermal Maximum, or PETM, period, the Arctic was a tropical climate and the summer water temperature in the Arctic Ocean was around 74 degrees Fahrenheit.

"The oldest and still the most popular hypothesis is that much of the carbon came from large deposits of methane hydrate, a peculiar, icelike compound that consists of water molecules forming a cage around a single molecule of methane. Hydrates are stable only in a narrow band of cold temperatures and high pressures; large deposits of them are found today under the Arctic tundra and under the seafloor, on the slopes that link the continental shelves to the deep abyssal plains. At the PETM an initial warming from somewhere—perhaps the volcanoes, perhaps slight fluctuations in Earth's orbit that exposed parts of it to more sunlight—might have melted hydrates and allowed methane molecules to slip from their cages and bubble into the atmosphere.

The hypothesis is alarming. Methane in the atmosphere warms the Earth over 20 times more per molecule than carbon dioxide does, then after a decade or two, it oxidizes to CO₂ and keeps on warming for a long time. Many scientists think just that kind of scenario might occur today: The warming caused by the burning of fossil fuels could trigger a runaway release of methane from the deep sea and the frozen north."