Posts Tagged ‘ice’
|In this week’s issue of Nature: “Earth’s biggest climate switch”
Thursday, October 22nd, 2009
A lot of us have been following the paleoclimatology literature examining changes in global temperatures and atmospheric CO2 over the past 60 million years, which can be deduced using different chemical signatures in ocean sediment cores.
One time period, in particular, is especially relevant to the discussion of rising CO2–a change between 33.5-34 million years ago (MYA) called the Eocene-Oligocene (E-O) transition.
What happened back then? Around this time was the first appearance of consistent polar ice on Antarctica. Before then, atmospheric CO2 levels were high enough that Earth’s climate was a hothouse, perhaps as much as 8-10 degrees C warmer than today. Antarctica was lush and green with forests.
The worry is that if we start approaching atmospheric levels of CO2 similar to those before the E-O transition, we may warm the climate to a condition where polar ice us unstable. That would be bad news because the loss of the Antarctic ice sheet would raise sea level by more than 60 meters.
This week, Paul Pearson and colleagues (who have done a lot of this great work) published a new article1 examining the E-O transition in more detail to see if it has any clues for our modern environmental challenges.
What did they find?
Tags: Antarctica, climate history, ice
Posted in climate change science, polar ice | No Comments »
In this week’s issue of Nature: Ice sheets thinning
Thursday, October 15th, 2009
Most people are aware that the loss of ice from land masses like Greenland and Antarctica have the potential to raise sea level. One of the current concerns about polar ice loss is that as sea level rises, ice loss is accelerating.How does this work? Much of the ice along the margins of these land masses is what we call “grounded” –it physically stuck on the rough land lying under the coastal ocean. Imagine a block of ice sitting on a dinner plate, which, in turn, is sitting on something rough like a carpet. If you tilt up one end of the plate just a bit, gravity causes the ice to slide off until it hits the carpet, where it gets stuck. Most of the ice block remains on the plate but a bit is wedged (grounded) into the carpet. This is what basically happens to many of the glaciers flowing off the Greenland and Antarctic land masses.
Here’s the bad news:
Tags: Antarctica, climate warming, Greenland, ice, sea level
Posted in climate change science, polar ice, sea level rise | 1 Comment »
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