Other things to look for besides the core recovery process: me changing our music selection through my phone deeply buried in my polar gear, the other guys taking walks to pass the time, me filming parts of the process for our documentary, and how I shoveled snow into the Styrofoam container to serve as packing material. As mentioned in a previous post, snow that falls on the surface of an ice sheet becomes glacial ice over time as it gets buried and subject to higher and higher pressure. One of the highlights for me in helping to drill the entire 200-meter-long ice core at PALEO was seeing the changes in the individual cores with depth. In the top 10-20 feet (3-6 m), the cores are still largely snow-like and have a consistency similar to a packed snowball. They are quite fragile and often break into several pieces during retrieval and processing, so extra care is made to keep them in the correct order and orientation.
With the limited snowfall at PALEO—less than 4 in (10 cm) per year on average—each core near the surface represents 10 or more years of snow accumulation. As you drill below this top snow zone, the individual grains of snow get larger as the pressure consolidates them into little bits of ice. You end up with cores that look a little like a snow cone in consistency and density, but they generally hold their core shape well. This stage, intermediate between snow and solid ice, is known as “firn”. By around 300 ft (100 m) in depth, the increased pressure from the weight of the overlying snow and firn has fused the icy grains of firn into a solid mass of ice. Each individual core is now much heavier as well due to the increased density, and this depth has ice that is over 2000 years old (based on dated cores from Dome C). However, the air that was originally in the gaps between the icy grains of firn becomes trapped as bubbles within the ice. These bubbles make the ice still largely opaque as a core, but individual flakes or pieces of the ice here can be quite beautiful in the sun.
These bubbles are also how we can use ice cores to reconstruct past atmospheric compositions: once the air gets trapped in the bubbles, it is preserved until we melt or crack the ice and release it again. As you keep drilling deeper below 500 ft (150 m), the bubbles in the ice and bubbles get compressed more and more (the bubbles here are at. 200 psi), and the cores become denser and more translucent, but also quite brittle. They are also very cold, as the temperature within the ice sheet here is near -60°F (-55°C). Luckily, there’s not much handling of the cores, although I did get a few spots of frost nip on my fingertips from gripping the cores during processing, despite wearing gloves. I did, however, discover a layer of volcanic ash in one core around 400 ft (120 m) down. Though the layer was very faint, anything in the ice that isn’t bubbles immediately sticks out when you’ve been staring at pure ice cores for several days. The ash probably came from an Antarctic volcano to the west in the Transantarctic Range and fell around 3000 years ago. Comparing this layer with known volcanic layers in other Antarctic ice cores may help us better date our PALEO core. Half of our PALEO ice core will go to Australian colleagues who will focus their analysis on cosmogenic nuclides, rare isotopes of elements that are created when cosmic rays interact with material on Earth such as the atmosphere. By tracking how these nuclides change in concentration over time, we can learn things such as how solar activity varied in the past (because a stronger sun means a stronger solar wind that affects cosmic ray penetration on Earth). The rest of the core will go to Italian and French researchers for more-standard ice core analysis, looking at water isotopes and trapped aerosols. Currently, the boxes of ice cores from PALEO are being held in a freezer shipping container in Australia, where some initial cutting and processing began to supply the Australians with their samples. Eventually, this container will be shipped back to France and make its way to Grenoble, although the COVID-19 pandemic may alter the timing of this shipping. Full analysis of the PALEO core and other samples will take over a year, with published results likely not for another year as well. In the meantime, I will do my best to provide intermittent updates as I can! As this post wraps up this series on EAIIST and my Antarctic research, I’d like to thank everyone for following along the journey. Please feel free to contact me through emails or my Twitter account, @petescientist (where I largely post Antarctic research photos and updates) if you have any questions in the coming months. I hope you’ve enjoyed the posts and have a bit better idea now of what happens in the field of polar science. 14mm Pink Ufo Glass Slide Bowl USA Fast Free Shipping SALE! 14mm Pink Ufo Glass Slide Bowl USA Fast Free Shipping SALE!,Fast Free Shipping SALE!
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Instituido según Decreto 55-2017, cuyo propósito es monitorear el avance de los procesos de Descentralización.