3454 - GREENLAND - ice melting and Northern Lights? Greenland lost enough ice in last 2 decades to cover entire US in 1.5 feet of water. Streams and rivers cut through the Greenland ice sheet, pouring water into the Arctic Ocean. The Arctic is warming faster than anywhere else on the planet, and the toll on Greenland's massive ice sheet is becoming clear.
-------- 3454 - GREENLAND - ice melting and Northern Lights?
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- Greenland has lost more than 5,100 billion tons of ice in the past 20 years, or roughly enough to flood the entire United States in 1.6 feet of water.
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- This extensive ice loss has contributed to half an inch of global sea-level rise in just two decades. The data covers the 20 years from April 2002 to August 2021 and is based on observations taken by the Gravity Recovery And Climate Experiment (GRACE) fleet of satellites, which launched in March 2002.
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- These GRACE satellites measure changes in gravity around the world, which reflect how mass is distributed around the Earth over time. This is how they are estimating changes to ice mass.
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- The GRACE data shows that Greenland's ice loss is most severe around the coasts, where the ice is rapidly thinning and toppling into the ocean. Ice loss is particularly stark on the West Greenland coast, where warming subsurface waters are thought to be intensifying glacial melt.
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- Greenland's ice melt is one of the main factors driving sea-level rise in response to climate change. Greenland is currently on track to contribute 3 to 5 inches to global sea-level rise by the year 2100.
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- For every centimeter rise in global sea level, another 6 million people are exposed to coastal flooding around the planet. On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century, so 400 million in total due to sea-level rise.
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- Greenland contains the world's only permanent ice sheet outside of Antarctica. Together, Greenland and Antarctica contain 99% of the world's total freshwater reserves.
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- If the entire Greenland ice sheet melts, it could raise global sea levels by a staggering 24 feet, meanwhile, Antarctica contains enough ice to raise global sea levels by more than 200 feet if totally melted.
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- After looking at the ice melting look up and see the northern lights. The aurora borealis is a vivid demonstration of the Earth's magnetic field interacting with charged particles from the sun. It's also beautiful, and worth braving a cold night out when visiting the high northern latitudes. A nice view to distract your cold wet feet.
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- Auroras are centered on the Earth's magnetic poles, visible in a roughly circular region around them. Since the magnetic and geographic poles aren't the same, sometimes the auroras are visible farther south than one might expect, while in other places it's farther north.
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- In the Northern Hemisphere, the auroral zone runs along the northern coast of Siberia, Scandinavia, Iceland, the southern tip of Greenland and northern Canada and Alaska. Auroras are visible south of the zone, but they are less likely to occur the farther away you go.
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- The Southern Hemisphere auroral zone is mostly over Antarctica, or the Southern Ocean. To see the southern lights, “aurora australis“, you have to go to Tasmania, and there are occasional sightings in southern Argentina or the Falklands.
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- Different ions make different colors. Aurora displays are created when protons and electrons stream out from the solar surface and slam into the Earth's magnetic field. Since the particles are charged they move in spirals along the magnetic field lines, the protons in one direction and the electrons in the other.
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- Those particles in turn hit the atmosphere. Since they follow the magnetic field lines, most of them enter the atmospheric gases in a ring around the magnetic poles, where the magnetic field lines come together.
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- The air is made up largely of nitrogen and oxygen atoms, with oxygen becoming a bigger component at the altitudes auroras happen, starting about 60 miles up and going all the way up to 600 miles.
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- When the charged particles hit these atoms, they gain energy. Eventually they relax, giving up the energy and releasing photons of specific wavelengths. Oxygen atoms emit green and sometimes red light, while nitrogen is more orange or red.
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- The International Space Station's orbit is inclined enough that it even plows through the heavenly lights. Most of the time nobody notices, as the density of charged particles is so low. The only time it matters is during particularly intense solar storms, when radiation levels are high. At that point all the astronauts have to do is move to a more protected area of the station.
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- Ironically, intense solar storms can actually reduce the amount of radiation around the space station, because of the interactions of charged particles with the Earth's magnetic field. Meanwhile, ISS astronauts can snap gorgeous auroral panoramas.
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- Voyagers 1 and 2 were the first space probes to bring back pictures of auroras on Jupiter and Saturn, and later Uranus and Neptune. Since then, the Hubble Space Telescope has taken pictures of them as well. Auroras on either Jupiter or Saturn are much larger and more powerful than on Earth, because those planets' magnetic fields are orders of magnitude more intense.
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- On Uranus, auroras get weirder, because the planet's magnetic field is oriented roughly vertically, but the planet rotates on its side. That means instead of the bright rings you see on other worlds, Uranus' auroras look more like single bright spots, at least when spied by the Hubble Space Telescope in 2011. But it's not clear that's always the case, because no spacecraft has seen the planet up-close since 1986.
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- Occasionally the auroras are visible farther from the poles than usual. In times of high solar activity, the southern limit for seeing auroras can go as far south as Oklahoma and Atlanta, as it did in October 2011.
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- A record was probably set at the Battle of Fredericksburg in Virginia in 1862, during the Civil War, when the northern lights appeared. Many soldiers noted it in their diaries. It is harder now than a century ago to tell when auroras are very bright, because so many Americans live in cities, and the lights wash out the aurora.
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- The northern lights look like fire, but they wouldn't feel like one. Even though the temperature of the upper atmosphere can reach thousands of degrees Fahrenheit, the heat is based on the average speed of the molecules. That's what temperature is. But feeling heat is another matter, the density of the air is so low at 60 miles up that a thermometer would register temperatures far below zero where aurora displays occur.
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- Auroras are relatively dim, and the redder light is often at the limit of what human retinas can pick up. Cameras, though, are often more sensitive, and with a long-exposure setting and a clear dark sky you can pick up some spectacular shots.
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- One of the most difficult problems in solar physics is knowing the shape of a magnetic field in a “coronal mass ejection” (CME), which is basically a huge blob of charged particles ejected from the sun.
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- Such CMEs have their own magnetic fields. The problem is, it seems impossible to tell in what direction the CME field is pointing until it hits. A hit creates either a spectacular magnetic storm and dazzling aurora with it, or a fizzle. Currently there's no way to know ahead of time.
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- NOAA has an online map that can tell you what auroral activity looks like on any given day, showing the extent of the "auroral oval" and where one is more likely to catch the lights. It could be a beautiful sight or it could knock out all your cell phone coverage. We’ll see.
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February 10, 2022 GREENLAND - ice melting and Northern Lights? 3454
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