Top 10 Antarctica Phenomena That Must Be Seen To Be Believed
- (1) Striped Icebergs
- (2) Blood Falls
- (3) Green Flashes
- (4) Other Antarctic Mirages: The Fata Morgana
- (5) Colored Snow
- (6) The Song of the Ross Ice Shelf
- (7) Aurora Australis (“Southern Lights”) & the STEVE
- (8) Sun Dogs, Moon Dogs, and Solar Pillars
- (9) Cool Antarctic Clouds
- (10) The Brinicle, aka the “Icy Finger of Death”
The astonishing polar realm of Antarctica seems to specialize in astonishing sights. Traveling here feels like entering another world entirely, and all the more so when you luck out with glimpses of a particularly enigmatic or unusual Antarctica phenomenon. Here’s a roundup of 10 of them!
Your classic image of an iceberg might be a shining white sculpture out at sea, and indeed that’s the typical appearance. But bergs, in actual fact, aren’t always pure white. Blue icebergs aren’t infrequently seen; that’s actually the color of pure, uncontaminated glacial ice, with pressure having squeezed out air bubbles and longer wavelengths of red and yellow being absorbed by the ice, reflecting shorter-wavelength blue back to our eyes. The white color comes from an iceberg’s hard-packed coat of snow.
More rarely seen are striped icebergs, with the background white coming streaked with bands of blue, green, yellow, black, and other strikingly contrasting hues. As Scientific American notes, these mainly derive from cracks in the ice that fill with seawater, which then freezes to form differently colored ice. Ice formed from frozen seawater—marine ice—typically contains far fewer air bubbles than glacial ice (formed from snow that gradually becomes denser and denser, eventually turning into ice, due to the pressure of overlying snowpack); that means these ice-filled cracks often appear strikingly blue.
Stripes of other colors may be due to seawater rich in algae or other organic matter, sediment, or certain minerals. Cracks that opened at the same time, infiltrated by seawater of the same composition, may produce stripes of one color, but if fissures form at different times, filling with marine ice with different characteristics, the berg may end up with multicolored bands.
Needless to say, a striped berg is a real coup to see…
The snout of the Taylor Glacier at Lake Bonney in the McMurdo Dry Valleys presents one of the most stop-in-your-tracks sights in all of Antarctica: the crimson spillage of aptly named Blood Falls. Once thought to be produced by algae, we now know that the gruesome hue of this one-of-a-kind polar waterfall is due to iron oxidation. Read all about Blood Falls here!
The almost mythic green flash is a flare of green seen low on the horizon above a concluding sunset. Actually, the “green” flash may appear in other colors, but an emerald hue is the most common.
Green flashes are rarely seen. You typically need a very flat horizon—seascape skylines are ideal—with quite clear air, to spot one, and their usual extreme brevity and often small size make them easy to miss even when they happen.
A green flash is a kind of mirage, produced due to light rays from a source (the Sun, in the green flash’s case) low in the horizon that are bent by atmospheric refraction and separated into different wavelengths that are then affected by atmospheric scattering. There are actually a few types of green flash, from the “classical” inferior-mirage smudgelike or ovalish flash to more rarely seen hourglass-shaped mirages with green upper sections and the columnar green ray.
Antarctica is a propitious place to look for the green flash: On a typical visit, you’re spending a lot of time on the ocean and along the coasts of islands and the Antarctic Peninsula, so you’re enjoying lots of sunsets over a flat, wide-open sea horizon. (The flat, wide-open ice sheet of the continental interior also technically provides a good stage for the phenomenon.) Furthermore, the dearth of air pollution makes it more likely you’ll be able to see a green flash.
And though green flashes, as we’ve said, are usually fleeting spectacles, members of Admiral Richard Byrd’s expedition in 1929 watched green flashes and the related green rim from the Little America base on the Ross Ice Shelf for more than a half-hour one sunset!
The green flash aside, the White Continent is also a great place for viewing other mirages in general. The low-level cold air over the ice sheets and pack ice sets the stage for an intense thermal inversion, with warmer air above; the result can be strongly bent light rays. Superior mirages can result, with inverted or erect images of an object appearing above it.
One extra-wild-looking kind of superior mirage that’s most commonly seen in polar regions such as Antarctica is the Fata Morgana. This is an often heavily distorted stack of multiple images, both right-side up and upside down, poised above the faroff object that produces them—an iceberg, for example.
It’s not just colored ice in the form of blue or candy-striped icebergs: Not all Antarctic snow is white. Down here you can see red, green, pink, yellow, and even gray snow. What’s the cause? Well, there are multiple ones, but the most significant is snow algae. You can learn more about what’s behind colorful Antarctic snow in this article.
You can’t hear it with your naked ear, but the Ross Ice Shelf—the world’s biggest ice shelf, and one of Antarctica’s defining realms—sings a song. Scientists made the discovery after monitoring seismic sensors that were installed on this vast expanse of coastal ice in the Ross Sea between 2014 and 2017. They detected a regular, eerie seismic hum of five or more cycles per second from a layer of firn (old compacted snow) near the surface of the ice shelf, produced by the near-constant winds blowing over the rolling, dunelike snowcover.
Research revealed that the pitch of the ice shelf’s song varied during storms that scoured and redeposited snow dunes as well as during a widespread surface-melt event. Antarctica’s ice shelves help “hold back” the continental ice-sheet glaciers that flow into them, and scientists hope that monitoring the Ross Ice Shelf’s song on an ongoing basis could help key them into shifts in the shelf’s stability and movement.
Really no better place than Antarctica to enjoy the Aurora Australis, or Southern Lights! Auroras are flickering nighttime color spectacles in the heavens that result from charged particles issued from the Sun in the solar wind colliding with atoms and molecules in Earth’s atmosphere, exciting them so that they release light. Often green, the Aurora Australis may also blaze and dance in shades of red and pink.
Given most Antarctic tourism goes down in the essentially round-the-clock daylight of the austral summer, a lot of visitors to the White Continent don’t see the Southern Lights. But “shoulder-season” visitation in, say, November or March, when you’re experiencing dark nighttime, can yield great auroral spectacles—though it’s the relatively few overwintering scientists and staff at Antarctic research bases who have the best opportunities, during that very long, very dark austral winter.
Rarely, another phenomenon known by the rather hilarious acronym STEVE—Strong Thermal Emission Velocity Enhancement—has been observed during Southern Lights displays in Antarctica. There’s much we don’t understand about a STEVE, which manifests as a glowing band of pink or red, but it doesn’t appear to be directly connected to an aurora; it’s thought to be a fast-flowing jet of plasma made up of very hot charged particles.
Ice crystals in the atmosphere over Antarctica refract light to produce halos, which come in a variety of forms. They include sun dogs (see featured image courtesy of NASA ICE), also called mock suns, which are blotches of light that appear flanking the Sun, sometimes as part of a visible halo ring. A bright Moon can produce analogous features called (you guessed it) moon dogs or mock moons.
Another kind of halo Antarctic visitors sometimes observed is the solar pillar, which is a beam of light seeming to project up into the sky above the Sun when it’s low on or below the horizon, or sometimes below a high-in-the-sky Sun.
Brilliant stargazing and aurora-viewing don’t exhaust the skywatching possibilities in Antarctica. While much of the White Continent has a very dry atmosphere, not particularly conducive to diverse cloud formations, some very striking clouds can be seen in the Antarctic.
For example, in the more maritime-influenced (and thus moister) and mountainous areas, including the Antarctic Peninsula and such Antarctic and sub-Antarctic islands as the South Orkneys and South Georgia, you might see the mesmerizing clouds known as föhn walls or föhn banks. These are sculpted cloudbanks lying atop ridges, peaks, or hill-crests as moist air is forced up their windward slopes, cooling and condensing to form these cloud-furls. As the air descends on the other, leeward slope, it warms and dries, so föhn walls sweep over topographic features like a wave and then have a pretty clear-cut “snout” where cloud formation is cut off by the descending air.
(This warming effect of so-called föhn winds has been connected to significant glacial melting on leeward sides of topographic barriers in places such as South Georgia and the Antarctic Peninsula.)
Antarctica is also probably the best place in the world to see nacreous clouds, also known as mother-of-pearl clouds. These are ice-crystal clouds formed high up in the stratosphere that glow iridescent shortly on the heels of sunset.
Although less commonly recorded in the Southern Hemisphere compared to the Northern, enigmatic noctilucent (“night-shining”) clouds have been seen during the Antarctic summer. Most visible at twilight, these clouds are even higher than nacreous clouds, situated up in the mesophere layer of the atmosphere in the vicinity of 250,000 feet above Earth’s surface.
Not something you’ll see unless you don scuba gear—and, furthermore, really luck out—the ice formation known as a brinicle certainly ranks among the weirdest and wildest of Antarctica phenomena. It’s sometimes called the “icy finger of death” or “icy finger of doom”: dramatic, sure, but it actually has a ring of truth about it, at least when it comes to the potential threat the brinicle poses to certain marine critters.
Here’s what we’re talking about: When seawater freezes, the ice crystals exclude salt, which means that sea ice comes laced with channels and pools of liquid brine. If that brine escapes—say, from a fracture in the sea ice—it will sink, on account its more concentrated salt content makes it denser and heavier than the surrounding seawater.
Also because of its extra-salty composition, that descending plume has a lower freezing point than the seawater around it, which freezes upon contact with the frigid brine. Thus a column of ice forms around the sinking brine as a kind of case: a brinicle, resembling an aquatic version of an icicle or a stalactite, dangling from the underside of the sea ice.
Here’s the sinister side of the brinicle. If there’s enough brine leaking out from the sea ice, and especially if there aren’t any strong currents going on, this finger of ice can extend all the way to the seabed. Not only that, but it may then continue nosing along on the seafloor, an advancing tendril of ice that can entrap starfish, urchins, and any other benthic lifeforms that don’t manage to get the heck out of the way. Icy finger of death indeed…
Some years back, a BBC film crew managed to capture the growth of a seafloor-reaching brinicle on video: Check it out! Mesmerizing, huh? And definitely a little bit creepy.
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