字幕表 動画を再生する 英語字幕をプリント 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.
B2 中上級 大きな融解。アラスカの永久凍土の根拠を探る (The Big Thaw: Ground-Truthing Permafrost in Alaska) 86 4 Jack に公開 2021 年 01 月 14 日 シェア シェア 保存 報告 動画の中の単語