Of farming, methane bubbles, and Antarctic glaciers

Climate-related studies continued arriving apace this week.

Writing in the journal Geophysical Research Letters, scientists warn that the Pine Island Glacier in West Antarctica is shedding ice four times faster than a decade ago. Scientists have been tracking the glacier, roughly twice the size of Scotland, with satellites for the past 15 years.

At this rate, it will mostly disappear within a century — six times faster than previous estimates. [See Newscom graphic at right.) And if it melts, seas will rise nearly double what the Intergovernmental Panel on Climate Change predicted for this century. (Depending on different CO2 emission scenarios, the IPCC's estimates for sea level rise range between 7.2 and 23.6 inches by century's end.)

Earlier this year, NASA's Robert Bindschadler, another glacier expert, told Yale's environment360 magazine that the Pine Island Glacier now flowed into the sea at a rate of 1 foot per hour, 50 percent faster than five years ago.

In the interview, he explained why glaciers in West Antarctica are so sensitive to changes in climate:

The warm water has an easier time getting to the glacier from the middle layer of the Southern Ocean, which is where the heat is. So the continental shelf is just at the right depth to allow that warmer water a small upward nudge to get up onto the shelf and it gets directed right towards the glacier. We’re pretty sure that this is why this part of West Antarctica is acting in such a dramatic way. The glacier is thinning rapidly and accelerating five to ten percent per year.

Also in Geophysical Research Letters, scientists from the National Oceanography Centre in England report that a 1 degree C warming of the Arctic current over the past 30 years is probably melting methane ice in seabed sediments.

Using sonar, scientists have discovered over 250 plumes of methane bubbles rising from the seafloor west of Norway's Svalbard archipelago. A potent greenhouse gas, methane is over 20 times more powerful than CO2. This is the first time that methane bubbles in response to climate change have been observed in the modern period, say the authors.

In the ocean, methane hydrates form at a depth where the conditions are just right. Those conditions include sufficient water pressure from above and the cold temperatures of the deep ocean.

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