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  • Permafrost covers roughly a quarter of the entire northern hemisphere

  • Unfortunately, it's also located in the most remote and hard-to-get-to places

  • so very few people actually have been to a permafrost region.

  • Because of that, it's often overlooked

  • Permafrost contains a huge amount of frozen organic matter

  • There's twice as much carbon frozen in the permafrost as there is in the atmosphere today.

  • As this permafrost thaws out, so to will the organic matter. Which will decay and release

  • carbon dioxide and methane to the atmosphere.

  • this will amplify warming due to the burning of fossil fuels.

  • Temperatures are rising twice as fast in the high latitudes as it is for the global average

  • So permafrost right now is beginning to warm up and its starting to thaw out

  • We went up to Toolik lake to do ground penetrating radar surveys to measure the thaw depth

  • of the permafrost, and we did this in order to validate our satellite radar product.

  • What we measure from space with satellite radar is actually the frost heave

  • as the surface layer freezes and thaws. As water in the surface freezes it expands, and the ground goes up

  • and as it thaws in the summer, the ground goes down. That tells us how much water has frozen and melted

  • in the active layer, or the thawing layer.

  • We have to make sure that what we actually measure from space is, in fact really what we think it is

  • and we do that using a ground penetrating radar

  • This is a radar that is about the size of a shoe box and you drag it along on the tundra

  • and it sends out a signal and it reflects off the frozen permafrost and comes back and it tells us

  • the thaw depth. It's very important to know how much ice is actually in the permafrost.

  • Permafrost, you can visualize it as frozen dirt, but within the permafrost there is a huge amount of ice

  • in the form of layers, and lenses, and wedges, and blocks.

  • Of course, when the permafrost thaws out, this ice melts and drains away and the soil collapses.

  • So it's extremely important to know how much ice is actually in the permafrost.

  • When talking about permafrost and permafrost change, there's two things that we look at

  • one is the temperature within the permafrost at various depths, and the second is the depth of the active layer

  • now as temperatures have been going up due to climate change the active layer has been getting thicker

  • which means its thawing deeper and deeper, but the bigger response is the permafrost itself

  • Permafrost itself actually takes a long time to respond to changes in climate

  • and the key think to realize about that is that as the temperature temperature of the permafrost goes up

  • nothing is going to happen to that permafrost until it reaches zero degrees centigrade

  • The permafrost temperatures right now deep down are actually still responding to little ice age 600 years ago

  • So as climate changes now permafrost is changing, but it's always going to be slow,

  • it's always going to take a long time.

  • So its going to take a couple of hundred years for this to thaw out, decay, and release the carbon dioxide

  • into the atmosphere. So it's going to take a long time, but also, once it starts, it can't stop.

Permafrost covers roughly a quarter of the entire northern hemisphere

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B2 中高級

大解凍。阿拉斯加永久凍土的地面真相 (The Big Thaw: Ground-Truthing Permafrost in Alaska)

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    Jack 發佈於 2021 年 01 月 14 日
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