字幕列表 影片播放 列印英文字幕 These are our polar oceans, a part of the world that is more foreign to scientists than the moon or Mars. But we are getting closer to discovering more about these crucial environments with advanced robotic technology. Dr. Alex Forrest is at the forefront of that work. His robots are built to access underneath ice shelves, and to gather data for large-scale maps and models that answer big-picture questions like, "How is a shoreline changing after a storm?" "How is toxic algae spreading?" And, "how fast is polar ice really melting?" The Nansen ice shelf is in Antarctica, down in the Ross Sea, and this ice shelf been an area of interest because it's breaking up. Basically, a piece of ice the size of Manhattan broke off and drifted off, and it exposed, in cross-sectional view, one of these subglacial channels that we've been trying to get access to for a while. We're aiming to go back there again with gliders and AUVs, to try to understand the turbulence and how much energy is being transported through that system. Energy is associated with heat, so if we understand how much heat is in that water, we can understand how much of that heat is coming from the ocean and how much of that is coming from the ice itself. To get a 3D picture of an ecosystem, Alex builds tools including Autonomous Underwater Vehicles, or AUVs with sonar, to make bathymetric maps. He then uses gliders to sample the water column providing him with turbulence, temperature, salinity, chlorophyll and oxygen data. What a glider will do, is move oil around to displace more or less volume to make it heavier or lighter than the water it's in. When it reaches an inflection point, it will pump itself light and then point upwards. The wings create a lift and start drawing it forward. In here is a satellite phone connector, a GPS receiver, and a free wave, or radio receiver. So we can talk to it when it's sitting up on the surface and tell it where to go from anywhere in the world. All together, these chemical and environmental fluid mechanic data create a comprehensive model of this ecosystem. Exploring these icy frontiers is a balancing act of keeping people and equipment safe in extreme weather and ocean conditions, bringing back accurate data, and preserving the very delicate ecosystem we want to study. One of the biggest challenges underwater is that we don't have positioning. We don't have WiFi, we can't get radio signals through, we don't have GPS... all of these tools that we use in regular, terrestrial mapping. You're basically guessing where you are underwater, so you need to develop navigation algorithms if you're using an underwater vehicle. Now, you put that on a ship, and then s@$%, you all of a sudden are influenced by the waves. So the waves, storms, et cetera will then modify how your data looks. What we don't want to happen is to have our vehicle modify the fragile ecosystem that exists at this water-ice interface. Despite these challenges, Alex and his team continue to gather this data as it is one of the clearest examples of how the planet's climate is changing every day. The polar regions are changing faster than anybody ever predicted. It's not just a matter of large pieces of ice shelves collapsing. What I find more intimidating is the idea that our sea ice volume is at some of the lowest it's ever been before; that the Arctic ocean temperatures are getting warmer than ever before; that all of a sudden, air temperatures are getting hotter. So we need to know the baseline conditions of today if we're to predict how they're gonna change and evolve in the future, and also to understand as a global community what we're losing.
B1 中級 探索極地冰蓋下所需的一切努力 (Everything It Takes to Explore Beneath Polar Ice Caps) 2 0 林宜悉 發佈於 2021 年 01 月 14 日 更多分享 分享 收藏 回報 影片單字