Hot and Cold Science

There’s an old saying that to make ice cubes freeze faster use boiling water in the tray rather than cold water as one might guess. Perhaps surprisingly, there might be some scientific truth to that…it’s called the Mpemba Effect.
The exact science behind this phenomenon is still being worked out and debated, however it raises some interesting questions. Last year Nature published a paper arguing that the Mpemba Effect doesn’t actually exist while another paper published earlier this year in the Journal of Modern Physics suggested that it does indeed exist, perhaps having to do with the structure of water collapsing when heated leading to more random collisions between molecules and thus faster cooling.

{If you’ve heard the old adage about the reverse phenomenon, that cold water will boil faster than hot water and are wondering if that’s true now, I’m sorry…that one has been proven false. Cold water does however bypass the hot water tank in your home and may taste better even if it takes longer to boil.}

But going back to the process of hot water freezing…
Another interesting phenomenon occurs when very hot water meets very cold air. Hot water contains more energy and has less structure (as explained by the above article in the Journal of Modern Physics). It’s actually closer to steam than cold water. So when it’s thrown into the air it breaks apart into tiny droplets each with a large surface area, facilitating the evaporation and freezing processes. Hot water thrown into cold air freezes almost instantly creating an impressive cloud of ice particles and fog. Try again with cold water and you’ll just end up with a puddle of ice on the ground.
Huffington Post published an article back in 2014 explaining this effect with some cool videos (www.huffingtonpost.com/boiling-water-extreme-cold-water-gun-ice). With the recent cold weather across the US I imagine there are lots of posts about this too.

This works best at temperatures below -40F and makes for some pretty cool photos. Unfortunately, we don’t have the bandwidth to upload videos here, so these pictures will have to do.

-90F at the South Pole on March 25, 2013:

South Pole March 2013

-50F at Summit Station on December 5, 2017:

 

-55F at Summit Station on December 1, 2016:

 

 

 

We also experimented with freezing bubbles. However, with no trees or mountains to break the wind it’s generally too windy for bubbles to last very long. It’s also been pretty cold lately at -75F last week so they freeze very quickly, often bursting.

 

If you’re looking for more fun science projects to do at home this winter check out this awesome post by NPR: www.npr.org/dont-just-shiver-here-are-3-cold-weather-experiments-to-try

And if you’re still interested in the science and history of cold check out the aptly titled, fascinating, and well written book: Cold by Bill Streever.

Rave Ice

Last winter I was in the midst of my monthly building checks when I went out to visit the Mobile Science Facility (MSF). It was a dark day and snowing lightly. I noticed a flickering light on the snow out of the corner of my eye and proceeded to the back of the building where there are no outside lights. In the shadow of the building and under the angled LiDAR beam the ground was alive with bright green flashes of light.

A starstax image

The LiDAR glows green atop the MSF

The MSF on 11/28

Taking IcePICs

The LiDAR laser is mounted to the roof of the Mobile Science Facility (MSF) and is part of the ICECAPS project which is looking at atmosphere, precipitation, radiation, and cloud properties over the Greenland ice sheet.
The science techs had noticed these reflected lights earlier, but I had not seen it before. It was truly magical! The lights danced and flickered around lasting only a fraction of a second. Some streaked across in lines, others just flashed a tiny spot, still others revealed intricate interference patterns on the snow. Later that evening the techs and I returned with our cameras. Like auroras, it’s difficult to capture the movement, but still beautiful and interesting none the less!

It was reminiscent of disco ball lights, but faster and brighter. At first we called it “Disco Ice,” but that wasn’t quite right…lasers, neon green, a high frequency pulse… “Rave Ice” was a better fit.

Intrigued, we decided to do some research to find out what exactly was happening. Was this a normal LiDAR by-product? How was it related to the falling or blowing snow? What did it tell us about current atmospheric conditions? Surprisingly we found almost nothing on the topic. One paper described a similar phenomenon, however the authors said it had only ever been observed in controlled optics research labs and computer programs, never outside. They speculated that snow or ice crystal size, shape, and orientation could be inferred from the light patterns displayed. One of the science techs wanted more information and reached out to the authors sharing some photos we had taken. They were amazed.
This phenomenon has most certainly been occurring since the LiDAR was first installed in 2010. However, it is rare, can only be seen in the dark, and had never been documented until last winter (2016-17). Over the next few months the ICECAPS Primary Investigators, the science tech here, and the optical researchers collaborated to write an article explaining the unique phenomenon. It was published in the July 2017 edition of Applied Optics!

They were able to link the patterns we photographed, the ice crystals we collected, and the shapes and patterns they had modeled in their labs. For example, a bullseye pattern is created by a smooth sided disc, while a bright spot surrounded by six broken dashed lines is a distinct hexagonal plate. We saw both of these patterns and also collected these types of crystals during the event.

It appears that this phenomenon occurs relatively often. When seen from afar the LiDAR beam glints and sparkles reflecting off the crystals. But conditions must be just right to get well defined patterns. There can’t be too much freezing fog, it can’t be blowing tons of snow, it needs to be dark, and there needs to be some precipitation. While any crystals will reflect the laser the most intricate patterns are a result of proper snowflakes and other more complex crystal shapes; something that requires relatively high humidity (so not too cold) and not too much turbulence (otherwise they’ll break apart). Up here it tends to be either very cold, calm, and clear with no precipitation, or warm, humid, and windy with far too much turbulence for complex crystals to form.
Earlier last week however there was an abnormally warm period with very low winds. Temperatures in some areas of Greenland were as much as 50˚F above average. While temperatures here have been around -50˚F the week prior and again this week, during the warm event Summit temps reached +7˚F! This warm spell affected much of Greenland and was so unusual it made the news:
https://thinkprogress.org/omg-heat-wave-scorches-greenland
https://weather.com/news

It also proved to be absolutely perfect conditions for Rave Ice. I had noticed the sparkling LiDAR beam on Tuesday afternoon and knew it would be worth hauling my tripod and camera out there. As I was walking out one of the techs called out on the radio that I should come out to see…and it was some of the best yet. I set up my tripod and started taking pictures while the tech collected snow samples, photographing the ice crystals, and recording meteorological data.

The science tech in the unheated shelter used to photograph ice crystals

Observing the Rave Ice

These are some of the crystals she photographed:

And these are some stacked images of the reflections:

Robot Boyz

Above all else Summit Station is a polar scientific research station. We are here for Science!
Much of the research done up here is in the vein of long term monitoring; an instrument is deployed to take measurements for months or years without needing specific personnel here on site aside from the Science Technicians. We have several suites of instruments from many different groups. Some measure black carbon in the atmosphere, others measure cloud height, type, and precipitation, there’s a lot of atmospheric monitoring in general, a seismometer, and several solar radiation sensors.
The other type of research involves bringing the researchers themselves up here – either to install instruments, drill cores, collect samples, or test new technologies. The flight periods are the busiest times on station with many groups coming up for just a few days or a week, but some groups stay between flight periods. This past month, between flight periods 4 and 5, we are supporting two PhD students from Dartmouth who are here working with a robot. The Cool Robot.

Their main objectives are to field test a new version of this robot, to prove that robotic surveys are feasible and practical. If they can be proven reliable robots could be used to track snow topography and elevation, ablation, accumulation, and all sorts of other parameters with significantly higher precision than the satellites we now rely on.
This particular robot is designed to follow a designated path while towing a ground penetrating radar (GPR) unit to measure compaction rates and densities. It is also carrying an infrared camera, which the researchers hope to measure exact surface area of the snow that can then be used to determine gas-air transfer rates. Finally, it includes a radiometer to measure the albedo of the surface – and thus how much solar energy it’s reflecting vs absorbing.

Solar panel patterns

Some of the issues they’ve had to deal with is the robot filling with snow in high winds, the tires sinking in soft snow, losing traction on hard snow, hitting steep drifts and getting pushed off course…it’s a sometimes slow process, but overall I believe they’ve had great success and have their issues to delve into this winter when they return home.
It’s a boxy little thing, covered in solar panels. It doesn’t move very fast, maybe a 5mph at most, and we’ve grown used to seeing it putter around camp from one site to another. Check out their webpage and field blog: http://sites.dartmouth.edu/polarregionsrobotics/field-blogs/greenland-2017

The “Robot Boyz” discuss annual layers in a back lit snow pit dug near station

Nacreous Clouds!

The sun is on its way back and while we still have 3 weeks until the first sunrise each day is a little brighter than the last. New Year’s Eve dawned bright and clear with crisp stars and a few very special clouds on the horizon. At first they were startling neon pink, orange, and red. The first real sign of the sun in weeks and a beautiful contrast to the greens and blues of the night sky and aurora. As the day progressed the clouds grew in size, becoming clearly iridescent. With no insulating clouds overhead it was a chilly -60F ambient. The cold temperature, otherwise clear sky, low sun, and wavy iridescent features all pointed towards these clouds being Polar Stratospheric Clouds (aka PSCs or Nacreous Clouds).

These rare clouds are both terrible and beautiful. Forming in the stratosphere at 49,000-82,000ft and at temperatures below -100F they are composed of water, nitric acid and/or sulfuric acid. While beautiful, they are implicated in the depletion of stratospheric ozone – an important protective layer against harmful UV rays. According to TheOzoneHole.com:
“PSCs were long regarded as curiosities and of no real consequence. However, Type I clouds are now known as sites of harmful destruction of stratospheric ozone over the Antarctic and Arctic. Their surfaces act as catalysts which convert more benign forms of man-made chlorine into active free radicals (for example ClO, chlorine monoxide). During the return of Spring sunlight these radicals destroy many ozone molecules in a series of chain reactions. Cloud formation is doubly harmful because it also removes gaseous nitric acid from the stratosphere which would otherwise combine with ClO to form less reactive forms of chlorine.”

Bright neon clouds

Polar Stratospheric Clouds – note their brightness, iridescence, and feathery/wavy structure

Measuring the ozone layer above us and the seasonal Arctic ozone hole is one of the many projects we support here at Summit. Every week the science techs launch a large balloon with a carefully calibrated instrument to measure ozone concentrations, as well as normal meteorological data (wind speed and direction, pressure, temperature, and humidity). The data is sent back via radio signal to the computer here at Summit.

Lidar

It was lightly snowing last night, ice crystals falling from high, thin clouds as I walked from the Big House to the Green House. Looking towards the MSF there was just enough ice in the air to illuminate the ICECAPS LiDAR – a laser measuring cloud matter, phase, and crystal orientation. ICECAPS is a relatively large, long-term project researching cloud characteristics and their impact on climate. This knowledge is crucial in developing climate models as well as understanding our changing climate. More information can be found here: www.esrl.noaa.gov/arctic/observatories/summit.

Most of the time the laser is invisible, however with just the right conditions enough light can be reflected back to show the brilliant green beam. If you look carefully you can also see the vertical laser, however this is weaker and thus less visible. Beautiful science!

*If you are familiar with LiDARs you may have seen this spelled LIDAR, lidar, LiDAR, or LADAR – according to NOAA’s Digital Coast Blog all spellings are correct though LiDAR is gaining in popularity. 

The ICECAPS LiDAR here at Summit

The LiDAR at NOAA’s ARO facility at the South Pole Station

 

An example of the LiDAR data:

Photo courtesy of NOAA: http://www.esrl.noaa.govarctic/observatories/summit

Halos

Auroras may grace the polar skies at night, but the day sometimes brings phenomenal halos and sundogs. It’s hard to describe the intangible beauty of these phenomena – vibrant spots of rainbow on either side of the sun, glowing pillars of light from the sun, a brilliant stream of light encircling the sky parallel to the horizon…a good display is simply awe-inspiring.

In general atmospheric optical phenomenon (sundogs, halos, rainbows) are not uncommon. Frequent halos and sundogs can be seen around the world when ice crystals in the atmosphere reflect and refract light. Infrequent halos are more often seen in polar regions or at high elevations with colder temperatures and more ice in the atmosphere. A common occurrence with halos is “Diamond Dust” which is essentially a ground level ice cloud filling the air with glittering ice crystals.

All photos below were taken by me, click on any of the images to open the full photo with caption.

22deg halo, upper tangental arc, and parhelic circle

22deg halo, 46deg halo, upper tangental arc, circumzenithal arc, and diamond dust

Parhelic circle, 22deg halo, 46deg halo, and upper tangental arc

The different crystal shapes generate different optics, however ice crystals form in hexagonal symmetry, thus while the crystal might be long or short (columnar or plate-like) the internal angles are always the same. Here at Summit the ICECAPS project, housed primarily in the MSF, is researching these crystals and cloud formations to better understand the complex processes involved in these systems.

The following website is a brilliant source of information regarding atmospheric optics and identifying features: www.atoptics.co.uk. An impressive full list of optical phenomenon can be found here: https://wikipedia.org/Atmospheric_optical_phenomena. For more Summit specific photos and information check out the Polar Field Services blog, Field Notes.

Photograph of a good halo display – 22° halo, upper tangent arc, 46° halo, and parhelic circle at Summit Station, Greenland

 

Below are some of my favorite photos of optics that I have witnessed in the Arctic and Antarctic. If only I’d had my wide angle lens in past seasons! Click on images to bring up caption and full picture.

And HDR image of the nearly setting sun at Summit showing sundogs and a lower sun pillar

A vibrant sundog over the Green House (Summit)

22 deg halo around a climber on the 50m tower (Summit)

A simple 22 deg halo over the South Pole cargo berms

Sundogs around the setting sun at Summit

Sundogs, a faint parhelic circle, and vibrant circumzenithal arc above (Summit)

Washed out, but very bright sundogs, a 22 deg halo, parhelic circle, upper tangent arc, 46 deg halo, and possible 120 deg parhelia (WAIS Divide, Antarctica)

 

According to atoptics.co.uk, 120° parhelia are infrequent, but not super rare. They are often faint and short lived however, I have only ever seen them twice. Below is a panorama at Summit showing bright 120° parhelia.

Bright sundogs, 22° halo, and definite rare 120° parhelia! (Summit)

Looking opposite the previous photo – the 120° parhelia can be seen along the parhelic circle (Summit)

Moon halos are not uncommon either, but require a nearly full moon and darkness as well as halo forming conditions.

Moon dogs around the Big House (Summit)

 

Other interesting optical phenomena include the green flash and fogbows. The green flash lasted a few hours at the South Pole Station in 2013 (check out my post from that sunset with more green flash photos here). This photo was taken through a telescope. It’s a bit blurry due to heat waves and light distortion near the horizon, the same process which causes the green flash to be visible. Fog and fogbows are a frequent occurrence at Summit, Greenland.

 Happy belated equinox and sunrise at Pole!

Around Mac Town

Ross Island dominated by Mt. Erebus in the center as seen from out on the ice shelf. McMurdo and Scott Base are located on the dark area to the left.

The weather in Antarctica is notoriously capricious, especially in the stormy West Antarctic, and its storms are legendary. Teams heading out to the “Deep Field” are brought into McMurdo several weeks in advance to complete training and preparations for the field, but also to give a buffer for deployment to field sites. Weather delays of a week, or two, or three are not uncommon especially when combined with ageing aircraft and shifting priorities with many groups needing to utilize flights. Once field preparations are complete we volunteer with other departments and projects and take advantage of the hikes and activities offered around the main USAP hub of operations. It can be frustrating at times to have clearly defined projects and goals and not be able to start. On the other hand most deep field camps are on the bright flat white so the majestic mountain views, hiking trails, and wildlife are savored while amenities like hot showers and warm dark rooms are appreciated. I wrote a post about McMurdo back in 2012 – not too much has changed : ) Check it out here: antarcticarctic.wordpress.com/mcmurdo-station-aka-mac-town and another here: antarcticarctic.wordpress.com/2014/11/10

Viewing the penguins from a distance…

Emperor penguins

A seal checking out a breathing hole

A Weddell Seal

CRREL: This year I’ve spent a fair bit of time assisting some friends with the Cold Regions Research and Engineer Laboratory (CRREL) as they conduct ground penetrating radar (GPR) and GPS surveys of the McMurdo area. One project is looking at the structure of the McMurdo ice shelf. With the airfields and runways built out on the flat ice it is an integral part of USAP logistics and would pose a huge problem should a large piece calve away unexpectedly. To do the survey we towed 200MHz and 400MHz GPR devices behind snowmobiles along predetermined transects using a precision Trimble GPS unit to record location and elevation. Ice cores were manually collected to determining the depth of the brine layer – essentially the ice depth at specific points. The cores ranged from 5-16 meters deep!
The sea ice, which may break up during the summer, is roughly 1-7m thick, while the ice shelf which remains frozen year-round reached depths of greater than 40m!

Cutting up sections of core to be taken back to the lab

Drillnig for cores…

The drill with 3 sections attached

Another project was examining the geology and bedrock structure of the McMurdo area in town. While there are still significant patches of ice and snow it’s starting to melt out and most of the roads are clear by now. We made an amusing sight: one person in the lead with a rope around their waist dragging a bright pink plastic sled loaded with a big orange box along the gritty uneven rock roads and hillsides…the other person walking next to the sled wearing a yellow backpack with a big antenna sticking out the top.

SPOT: The South Pole Traverse is heading out around this time of year too so there is a lot to do to help them get cleaned up and on the ‘road’ to Pole. I spent several days helping the SPOT teams reorganizing drums and securing cargo to their sleds. While their set-up is much larger and more complicated than ours will be, the theory is all the same and it was good to re-familiarize myself with the Cat Challengers, though the ones we will be using at WAIS are far older and a bit smaller. See my previous post for more information on SPOT: Antarcticarctic.wordpress.com/spot

Dive Tending: One morning I got to assist the Divers. On that particular day they were recording water column visibility along a steep drop-off not far from the station. We met in town and loaded up a Pisten Bully with all their gear and supplies. Out on the ice we stopped at one of the “Fish Huts.” Small brightly colored buildings, the heated huts sit over maintained holes in the ice at designated dive points. Bundled up in long underwear, a full insulated down suit, and a sturdy dry-suit the two divers were uncomfortably warm while we got everything ready. Gear was brought inside the hut and a line was tied off to the hut wall and then lowered into the water with strobes, flags, and an emergency air tank. In the dim light under the ice and with very limited places to surface it is imperative not to lose the dive hole! Then sitting at the edge of the hole, with practiced efficiency, they pulled on their hoods and masks, strapped on their weights and flippers, locked on their thick lobster-claw mittens, and hoisted on their air tanks and regulators…and then they slipped into the hole!

McMurdo_Sound#Life_below_the_ice

With a burst of bubbles they sank down the 3-4ft hole through the sea ice and disappeared into the dark water. Once they were gone I lowered the ladder and closed the shutters of the hut. The sunlight filtering through made the ice glow an electric blue around the black water. The dive lasted about 20 or 30 minutes as I watched from above noting feathers, or platelets, of ice growing on the surface of the ~28F water and keeping an eye out for the divers as they swam under the hole.

The second diver about to enter the water

Before I knew it there was a mass of bubbles and one of the divers appeared in the hole. I assisted with hauling out their heavy air tanks so they could climb the ladder and warm up next to the stove. Then it was back to town in time for lunch!

Pressure Ridge: An interesting feature in the McMurdo area is the pressure ridge. An area of ice that’s been forced together by ice flow and tidal movement it forms each year right in front of New Zealand’s Scott Base. With unrelenting pressure the ice is driven into the air cracking and breaking to form stunning features – the snow bright white and the ice glowing a deep blue. With so much relative ice movement thin spot and air holes form making it very popular with the Weddell seals in the area.

A friend’s website with some amazing photography of pressure ridges and more can be found here: www.benadkisonphotography.com/antarctica

Ob Tube: The Observation Tube (aka Ob Tube) offers a unique glimpse under the sea ice just in front of McMurdo. A tube, anchored to the ice surface, houses a ladder down 10ft or so to the base where there is a small round area with windows. Not for the claustrophobic, it is a tight fit and is quite dark. Some light filters through the ice to illuminate sea stars on the ocean floor while tiny fish, jelly fish, and pteropod “Sea Angels” float past the thick ice rimmed windows. Perhaps most notable is the texture of the sea ice base. While the top of the sea ice is a varied terrain of snow, blue ice scoured clear, or area of melt later in the summer, the base is comprised of delicate sheets and leaves of ice called platelet ice. The seawater is below freezing here at ~28-29F on average and as the fresh water freezes a salty shimmering brine solution is formed just below the ice level.
Later in the summer the ice will thin and possibly break up here so the Ob tube is a temporary feature only deployed for a few weeks in November.

The Ob Tube and Ob Hill

Feathery new ice underneath the sea ice

Check out this post from a fellow polie about the Ob Tube here: http://davidpablocohn.com/ob-tube

Arrival Heights: Arrival Heights is an area just Northeast of McMurdo Station proper, not far from the Castle Rock hiking loop trail. It is an area reserved for clean air sampling and radio and light sensitive experiments – a bit like Summit’s Clean Air Sector and South Pole Dark Sector combined. Several special camera suites study auroras so in the winter the use of lights is kept to a strict minimum. Other experiments are looking at the ionosphere and magnetosphere (space weather) utilizing huge antenna arrays which are highly sensitive to radio transmissions.

As an Antarctic Specially Protected Area (ASPA) it is off limits to the public at large, however occasional guests are permitted as long as they are accompanied by official personnel and traffic, either by foot or vehicle, is limited to designated routes only.
Exposed to some brutal winds it also offers one of the most beautiful views with the Royal Society Mountain Range clearly visible to the West and unhindered views North towards Cape Evans and the sea ice edge.

 

Cape Evans:
About 20km North of McMurdo Station on Ross Island is Cape Evans. Named for Robert Falcon Scott’s second-in-command Lieutenant Edward Evans it was the staging point for the British Terra Nova Expedition of 1910-1913 .
The expedition’s hut, now dubbed Scott’s Hut, was prefabricated in England and reconstructed on Cape Evans in 1911. It was built to house the 25 men of the expedition during the following winter while they prepared for the journey inland. With lessons learned from Scott’s previous, and frigid, Discovery Hut (located on Hut Point, just a short walk from McMurdo Station and used by Scott during the 1901-04 Discovery Expedition) the 1911 Cape Evans hut contains two stoves, better insulation, and is surrounded on some sides by a covered stable and storage area. Some of the men reported that it was “warm to the point of being uncomfortable.”
In the austral spring of 1911 Scott and several of his men set out to be the first men to reach the South Pole. For more information on that check out this fantastic 2011 article Race to the South Pole by the National Geographic. They arrived on January 17, 1912 to find a tent and a note from Roald Amundsen who had reached the South Pole first on December 14, 1911. Their dreams dashed, they headed towards the coast, however suffering from malnutrition and cold injuries there were no survivors.

This is of particular historic significance as it was this brutal expedition that arrived at the South Pole (just behind Norwegian Roald Amundsen) and from which Scott never returned. Several men remained at Scott’s Hut for the winter of 1912 to search for Scott’s party, however in 1913 they left Antarctica as well, leaving Scott Hut stocked with supplies.

The Hut was used again in 1915-17 by 10 men from Ernest Shackleton’s Ross Sea party after their ship, the Aurora, with the rest of the crew, broke adrift and was taken North in the ice in May 1915. The Ross Sea party was the counterpart to Shackleton’s 1914-17 Imperial Trans-Antarctic Expedition expedition, the ill-fated attempt to cross the continent. They were responsible for laying supply depots for Shackleton’s return from the Pole, however Shackleton trapped in the ice aboard the Endurance, failed to ever reach the continent itself and so the entire effort was for naught.

Due to sub-freezing temperatures, low humidity, and conservation efforts by the US and New Zealand and the Antarctic Heritage Trust both Scott’s Hut and Discovery Hut have remained much as they were left in the early 20th century; Beds are made with shoes tucked beneath, a desiccated and partially dissected penguin lies on a table, glass vials of medicine and solutions line shelves while the kitchen is well stocked with tins and cartons of various food stuffs. A massive pile of seal meat is stacked out in the covered storage area, fairly well preserved for being over a hundred years old, though smelling a bit rancid…The entire site is full of amazing artifacts from the expedition such as snowshoes for their ponies, and cartoons tacked to the wall.

Check out Amusing Planet’s page on Scott’s Hut for more information on the hut’s artifacts and the expedition in general: www.amusingplanet.com/captain-robert-scotts-hut-in-antarctica.html

Rations and supplies

Capt. Scott’s Antarctic Expedition 1910

A candle and toothbrush

A penguin being studied

Crates in front of the hut

The well stocked kitchen

Cartoons and pictures

Scientific equipment

More ration boxes

Weather boards on the outside

Scott’s Hut

Aurora Australis

Aurora Borealis and Aurora Australis – the Northern and Southern lights respectively – are one of the most iconic phenomena of the polar regions.
Dancing streams of light, ephemeral and enchanting, appear in the dark sky spanning a spectrum of color from white to green to red and near purple. They have fascinated mankind and until recently were thought to be spirits or signs from god. Today we understand the physics behind aurorae, however this explanation is no less amazing. It is still one of the most awe inspiring natural phenomena I have ever witnessed.

A nice diagram showing the magnetosphere and solar wind

Charged particles emitted by the sun reach Earth and are diverted around the magnetosphere. This strong magnetic field is induced by the spinning mass of liquid iron in Earth’s core and acts like a shield protecting Earth from the solar wind. Without the magnetosphere our atmosphere would be blown away and terrestrial life would be exposed to extreme radiation emitted by the sun. The magnetic field lines originate and converge at the axis of Earth. Solar particles are charged so they follow the magnetic field lines and are essentially funneled into the atmosphere at the Poles.

The interaction between these charged particles and atoms in our atmosphere produces light. This phenomena occurs year round, but the light is only visible in the dark of night. Here at the South Pole we have one long day and one long night each year – so the auroras are only visible during the winter months.

Auroras as seen from space

An image of auroras from space

NOAA’s space weather forecast showing the aurora oval – where auroras are most likely to occur.

Walking out to the berms to check on something or find more supplies, I watch the sky above me. With no light the stars shine brilliantly, the sweeping arc of the Milky Way plainly visible. My breath hisses in the cold, my eyelashes freezing together, my steps crunch loudly on the ultra dry snow. I glance up to see a slight glow, a pale green that gradually brightens as it expands. Other bright spots appear and it unfurls in a long curtain of light – reddish at the top and green at the bottom. It seems to stream downward, undulating and pulsing, curling upon itself in sections only to unfold again. It moves across the sky sometimes breaking into parallel lines. After a while it fades away again leaving only the darkness and pure starlight behind.

During winter everyone on station carries a personal radio with them. We can call each other individually, in programmed groups, or do an All Call. With some people working nights and others “free cycling” (for example researchers who do not have to stick to a regular schedule and instead follow a 27 hour day) All Calls are reserved for emergencies only. One of the programmed groups is “Aurora Lights.” This is a channel used to announce especially good auroras. A few months ago, when it was just getting dark, everyone would go running to the upper deck at DA when there was an aurora call. Now that we’ve passed midwinter people are starting to get a little jaded. Only an especially good aurora will draw a crowd…

This past Monday however, we had a spectacular show. Here are some pictures from myself and others here on station (as referenced):

Auroras over DA from May

Auroras over DA

More auroras from this Monday

A gorgeous shot by our Research Associate Andrew

Another nice pic with a fisheye by Andrew

Auroras over the station photo by IceCuber Felipe

Another shot by Felipe

The South Pole Telescope with auroras and the Milky Way. Photo by our power plant mechanic Eddie

An awesome picture Robert Schwarz shot this week of some nice auroras and a meteor!

Home Sweet Home from the top of the ARO tower

Yukimarimos!

Last week I was walking to the End of the World to help our station manager Weeks dip the fuel tanks when he noticed something unusual – small balls of snow all around us. “Yukimarimos! Haha, not really…those are just ice chunks…They’re way too big to be yukimarimo” He had seen them before, but only around sunrise/sunset. I got down on my knees turning on my red headlamp and gently reached my thick mittened hand towards one. At the slightest touch it rolled away from me picking up speed in the gentle wind. “What?! They really are Yuikimarimos! Those are HUGE!” I turned my head, illuminating dozens surrounding us, some easily 3-4inches (8-11cm) in diameter. They jostled together and rolled off into the darkness in the light breeze. Tiny ones only centimeters across filled in our footprints behind us. It was ~85F below zero with 5 or 6 knots wind.

The Haz Shack, Store DNF, Cargo DNF, and Cargo office on the way out to the fuel tanks

After lunch we returned to dip more fuel tanks, a very cold task. This time we were joined by a band of excited Yukimarimo hunters armed to the gaiters with red headlamps, tripods, and cameras that would die in the cold after half an hour. I tried to pick one up, but my clumsy oversized mitten crushed it completely. Pulling off my mitten I gently cradled another in my soft glove liners. It was a 3 inch snowball light as air, long hoar frost crystals held together by static electricity. “I dare you to eat it!” Weeks joked, I pulled down my thick fleece neck gaiter that covered my nose, cheeks, and mouth. “No! I was just joking! It’s -85F!” The Yukimarimo melted at the hint of my breath, leaving naught but a drop of water in my mouth. A ball of air held together by frost.
A while later our meteorologist, Phil, found a cache of them hiding under the station itself.

Congregations of yukimarimo under the station

This tricky phenomenon has only recently been scientifically documented (1997)and requires very specific environmental conditions – only forming in the heart of the Antarctic plateau in winter.

“These balls of snow form best deep in the Antarctic winter, when the air temperature is below minus 60 °C (minus 76 °F), and there is a gentle wind blowing – conditions under which even well-equipped polar explorers stay in heated buildings. In this frigid environment, delicate needles of hoar frost form on the surface of the snow. Some of these are rolled about by the wind and create these fragile snowballs, which grow to a size of about 30 mm”

“The researchers gave these dainty formations the name ‘yukimarimo’. ‘Yuki’ is the Japanese for snow, and ‘marimo’ is a globular water plant found in a lake in Hokkaido, Japan’s northern island.”

The full article in Nature can be found here:
http://www.nature.com/news/1999/990902/full/news990902-9.html

A yukimarimo – photo by Blaise Kuo Tiong

A little blurry and the light’s not great, but that’s part of my plastic ruler that shattered in my pocket…

My mitten next to a large one

Many little yukimarimos gathering between sastrugi

The expediton: Daniel, Phil, Blaise, Myself, Andrew, and Kris in front

Sunset at the South Pole

March 21, 2013: The Equinox – the technical date that the sun, as a point, sets at the South Pole. On a perfectly spherical earth, with no topography, no atmosphere, no height above the ground the sun would be exactly halfway below/above the horizon on this day …Of course this isn’t the case, so our sunset is a little more variable. Since reaching a peak height of 23.5deg (the tilt of the earth) on the December solstice the sun has slowly spiraled towards the horizon. For the past few weeks we have witnessed increasingly beautiful displays of gold, pink, and purple light. Shadows stretch exponentially and the sun spins around us, just skimming the horizon, moving as much as 15deg an hour. Inside it has become noticeably darker, with lights turned on in the galley and my room nearly dark at night. This is a pretty big deal for us winter overs as the sun rises and sets only once a year here at the South Pole – events witnessed solely by those who commit to winter here, a total 1389 people (197 women)since 1957.

A good visual (thanks wikipedia) of variuos dusk/twighlight terms.

Due to a combination of phenomena, the sun is still visible today and will likely remain so for a few days yet. Even after the orb ducks below the horizon we will have a few weeks of light, phasing from daylight to civil twilight (0-6º below horizon) to nautical twilight (6-12º below) astronomical twilight (12-18º below) and eventually to full darkness. The moon rises and sets on a two week cycle, the brightness of which can be significant, so we will not be in full darkness for the entire winter. That said, it will be pretty dark for a good ~4 months.

The next moonrise is March 26th, but the sun won’t show it’s light again until the next equinox (vernal for us in the Southern hemisphere, autumnal for those of you further North) on September 21, 2013.

The latest update from the Coldest Journey which has just begun their trek to the Pole:
www.thecoldestjourney.org

A few factors that influence the actual sunset are variable topography, air densities, and thermal inversions. The topography at the South Pole is not completely flat and uniform as it might seem, gradual undulations over miles create nearly imperceptible hills and valleys. These become noticeable this time of year with the sun appearing to be right on the horizon at noon and a few degrees above at 5pm. Strong thermal inversions exist here as well which can significantly refract the light, making the sun visible many days after it has technically set. The refractive effects of our atmosphere can make the sun appear to be flattened or squished against the horizon, or deceptively higher than it actually is, and is the cause of the green flash (LOTS more on the green flash and refraction here: http://aty.sdsu.edu/) – a phenomenon that has been visible for several hours in past years. Today it’s quite cloudy, but here’s a photo of a green/blue “flash” taken in 2000 by Rodney Marks:

And some more from 2003 (photographer unknown):

And here are some of my photos of the sun taken this year:

And so begins the longest night…