Polar Stratospheric Clouds.

Polar Stratospheric Clouds - Mawson Antarctica 

Polar Stratospheric Clouds.
The annual formation of the ozone hole in the southern polar region is associated with the development of polar stratospheric cloud.

Atmosphere temperature (Red)  and humidity (Blue) 26th June 

Formation of these clouds occurs between Latitude 60 degrees South and the pole and between 10km and 25km above the surface. Temperatures in the stratosphere need to be colder than -75 degrees C. Their movement is west to east. Formation occurs from mid-June to mid-October.

Type I Nacreous Cloud

Two types of Polar Stratospheric cloud can occasionally be observed from Antarctica.

Type I are thin layer clouds made up of small droplets of nitric and sulphuric acid and will form in temperatures colder than – 75 degrees C. They appear as a thin yellowish veil with fine horizontal structure and a bright spot a few degrees above the horizon scattering light from the sun. Orange haze above the horizon indicates scattering from nitric acid particles.

Type I and II Nacreous cloud.

Type II Nacreous Clouds or Mother of Pearl clouds and are made up of ice crystals below -83 degrees C. They have a pearly-white appearance due to scattering of sunlight and may show delicate interference patterns and pink and green colours.

They are best observed when the sun is between 1 and 6 degrees below the horizon during civil twilight. At that time the lower troposphere is in shadow while the stratosphere is still lit by the sun.

So what is the connection with stratospheric clouds and ozone depletion?  

Atmospheric layers in the Antarctic winter. © Dr. Andrew Klekociuk, Australian Antarctic Division

Each winter a polar vortex forms in the stratosphere over the Antarctic. The polar vortex is a region where air undergoes little mixing with the rest of the atmosphere, allowing temperatures to drop to around -85ºC and stay low. This occurs when there is no sunshine in the winter months during the polar night. The low temperatures allow water and other chemicals to condense, producing stratospheric clouds.

The polar stratospheric ice clouds provide a surface on which chemical reactions take place that lead to ozone depletion. Compounds called HALO CARBONS are converted to compounds that will catalytically destroy ozone. In spring when the sunlight returns to Antarctica, the destruction of ozone within the polar vortex starts and rapidly accelerates. The thinning of the layer of ozone is what is referred to as the ozone hole. It reaches a maximum in early October and slowly declines so that things have returned to normal by the end of December.

Wind profile 26th June. (1m/s = 3.6km/h)

The ozone depleting compounds contain combinations of the elements chlorine, fluorine, bromine, carbon and hydrogen. The general term for them is HALO CARBONS. Compounds that contain only carbon, chlorine and fluorine are called CHLOROFLUOROCARBONS (CFC). Compounds that contain carbon, bromine, fluorine (and sometimes chlorine) are called HALONS. From the surface stratospheric clouds seem to be stationary however wind speed can be strong. On 26th June speeds were up to 180 km/h 25km high.

Orange glow of nitric acid cloud droplets

Nacreous I and II cloud and drifting snow

Moon through Nacreous I cloud

Orange glow of nitric acid cloud droplets

Mother of Pearl Nacreous cloud type II -  Mawson 26th June 2011

Winter Solstice - Midwinter at Mawson

Mid Winter Preparations.

Mawson mid-winter preparations are in full swing. The traditional mid-winter Olympics competition kicked off on Saturday the 18th June 2011 with volleyball and volleyball soccer competitions and in the evening a trivial pursuit contest.

 

Mid-winter dinner menu.

Scotty the chef has been busy preparing for the 10 course banquet, and an extra slushy has been rostered on to assist in the week leading up to the 21st June.

Cutting the hole (Chris Wilson)

Removing the cut sea ice. (Chris Wilson)

RMIT van, container and pool.

Swimming pool with ice forming on the surface.

Team 'dieso' has been setting up the aquatic centre for the mid-winter swim. The work involved cutting the swimming hole but leaving about 20cm to remove on the morning of the swim. Cutting was done with a chain saw and blocks removed by the JCB fork lift vehicle. The end result - an aquatic centre boasting a 3m x 3m pool to an estimated depth of 10m, 1.5m sea ice walls, a small container for an undressing room, an outdoor spar pool and a heated RMIT accommodation van used for dressing after the swim. You would have to go a long way to find better facilities.


The Interment.
The interment ceremony for Phil Law and his wife Nellie was conducted on Sunday 19th June 2011. Phil was the first director of The Antarctic Division and under his stewardship the first Australian antarctic base was established at Mawson in 1954.

Interment service. (Chris Wilson)

Four cairns on West Arm

The Nella Dan, the Danish resupply ship that resupplied Australian antarctic bases for more than 25 years, was named in honour of Nellie Law. The ashes of Phil and Nell Law were placed in a cairn on West Arm overlooking Horseshoe Harbour alongside three ANARE men who have died while at Mawson.
A setting full moon, a stiff SW breeze and a mid-winter mackerel sky with a blaze of pink, orange and yellow provided the backdrop to the short service. ABC link, AAD link.

Mackerel sky, setting moon and a stiff breeze.

Cairn for Phil and Nellie Law.

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Mid Winters Day.

Mid winters twilight

Mid-winters day arrived with an amazing aurora display followed by a clear sky except for some high cloud on the northern horizon that made for a great orange pink twilight sky. A video conference with other stations was held at 10:00 Mawson time, followed by a special brunch and then to the sea ice for a swim.

Leopard Seal watch

Air temperature was around -19 degrees C wind 5-10kts and relative humidity at 70%. The water was much warmer than air temperature at about -2 degrees C. The pool was set up with a ladder and non-slip mats, the doctor was on hand if there was a problem and a large hot water spar was parked a short distance away to warm up after the swim. Two expeditioners swept the pool surface regularly to stop the ice forming on the top and one expeditioner roped up each swimmer so that they could be pulled out if required.

Sweeping the ice from the surface.
Swim photographs (Ian Phillips)

BoM weather data for Midwinter.

Spa (Ian Phillips)

A couple of hardy souls went back for a second and third swim. After the swim that was very invigorating it was tidy up and back to the Red Shed to prepare for the mid-winter dinner.

The Dinner
Midwinters dinner at Antarctic bases rivals Christmas dinner by way of importance and preparation.Great effort is put into the menu and the chef prepares weeks ahead of the day to ensure the dinner is of the highest standard. The table was set with appropriate cutlery, crockery and a decorative ice axe.

Mid Winter table

Pre dinner drinks in the mess at 3pm before the 10 course banquet commenced at 4pm, the last course was delivered around 9pm.

Official midwinter photograph (Ian Phillip)

First course.

Scotty prepares the first course.

 To add to the occasion, the station web cam was set up in the mess all day so that friends and family at home could get a sense of what was happening during the day. From the comings and goings at breakfast, brunch and the setting of the dinner table, pre-dinner drinks and dinner were captured and displayed on the Internet each 2 minutes.  

Setting (Ian Phillips)

The Dinner (Ian Phillips)

Ice Axe.

Decorative Ice Axe (Ian Phillips)

At mid winter gifts are often exchanged, however it was decided early in the organisation of mid winter activities at Mawson that a communal gift would be given. The gift, made at the station by expeditioners was a decorative ice axe with the name of each expeditioner carved on the handle. Over the past few months on Saturday afternoons the Deiso's workshop has been a hive of activity as the ice axes were being fabricated.

After dinner Rolf presented a retrospective slide show of Mawson in 1962 when his father John, wintered as an Electrician. It was interesting to note that problems encountered in 1962 are experienced in 2011 and the quality of good photographic slides compares well with the best of todays digital photographs. After Rolf's presentation the unnamed Mawson Band led by Tom put on a concert at the bar. It was a fitting conclusion to the midwinter program and what had been a great day. Of course the party continued into the night.

Mawson Band (Ian Phillips)

A Dream or a Nightmare?

Emperor Penguin at Auster.

I woke this morning in a dream. I was flying across snow and ice, it was dark and the way ahead was lit by white light. When I looked down I saw a red quad bike, I was driving it. Then I felt the sensation of the ice beneath the wheels – up down up down as the frozen waves passed beneath me. Every now and then a white snow drift would appear and I would be tossed up and down violently as I crossed it. Then long stretches of deep corrugations in the snow (sastrugie) shook the quad with a constant shudder that required me to stand on the foot posts to absorb the shock in my legs. Was this a dream or a nightmare?

As suddenly as the shaking started it stopped.  I was now gliding across flat almost polished sea ice, ahead of me now was an everlasting pre-dawn glow. The sky grey, then mauve and orange to the horizon, at the brightest point was the epicentre of a spray of high cloud, streaming overhead and away behind me. The cloud lit from beneath, its structure a splash of red orange and pink.  I travelled on and on and on. It was a dream.

Everlasting pre-dawn glow.

Suddenly I was hanging on for all that it was worth to control a bucking, pitching machine that was now thrown around more violently than before. At the same time I became aware of my declining vision. At first the edges started to blur and then I no longer was able to focus on the surface in front of me. All around became a blur of white. Was it blowing snow- a blizzard, no it was the condensation of my breath gradually freezing on the visor of my helmet. The visor heating has failed, I slowed my speed. Darkness was still with me except for the distant glow of twilight.

I was in a frozen wilderness, the wind was strong, the temperature 17 below zero.  I became aware of a red light ahead of me travelling in the same direction. I followed the glow trying not to lose sight I didn’t want to stop for fear of losing them. After some time of travelling blind I had suddenly caught up. The light had stopped. As I pulled up alongside and lifted my visor there were 5 other quads. I gestured my problem.  In a short while we had swapped quads, plugged my helmet into the socket and suddenly I could see again.

6 Quads.

The other quad riders were dressed just like me, bright coloured goose down jackets and large heavy black glacier boots with thick mittens for the hands.We headed off together into that predawn glow.

I was now sitting on the snow with two strange animals approaching me. They walked upright, with a slight waddle on short legs. As they got closer I could see that they were Emperor Penguins and soon there were others also. They had come from a huddle of thousands of birds located in an amphitheatre formed by large blue icebergs. I checked my watch it said 12:00 on 11 June 2011. 

We had come to visit Auster Emperor Penguin Rookery - a day trip from Mawson that took 8 hours - 7 of riding on the quad.The day length was 58 min 27 sec so most of the trip was in darkness. When travelling on quads we carry navigation equipment, radio's our survival pack as well as fuel, and recovery equipment should a quad end up in the sea.

Auster Emperor Penguin Rookery

The Southern Lights - Aurora Australis

Wind Turbine looking North - Mawson

Monday 30th May 2011.

Word went around that there was an active auroral display in progress, it was about 8:30 pm. I had been waiting for an opportunity to photograph an aurora at a reasonable time of night. I often see them out of my bedroom window late in the night and more recently in the early morning when starting work, but I needed a couple of hours to play with various camera settings to get acceptable photographs.

So after quickly dressing up in full kit to keep warm in the -20 degrees C outside I set off. There was a display that was in decline and although disappointed I was able to determine the settings needed on my camera. Just as I was considering packing up the intensity of the aurora increased and over the next hour I was transfixed by an amazing display.

The Ionospheric Prediction Service describes the Aurora a spectacular natural phenomenon occurring in the earth's upper atmosphere, associated with powerful emissions from the sun and geo-magnetic disturbances. They are seen mostly at high or polar latitudes but, occasionally may be seen at middle latitudes when a really large event occurs. For example, during a huge disturbance in March 1989, there were aurorae seen over northern Australia in Exmouth (WA) and in the northern hemisphere, as far south as Texas.

Aurorae are caused by high energy charged particles from the sun, such as electrons, entering the magnetosphere of the earth. This is most likely to happen during a geo-magnetic storm, resulting from the bombardment of the earth by solar particles following a Coronal Mass Ejection (CME).

Once within the magnetosphere, the solar particles interact with the earth's magnetic field, spiralling around the field lines and following them towards the poles…. and are also drawn downward into the ionosphere. In the ionosphere, they strike molecules and atoms of air at around 100 kilometres from the earth's surface (ego, Nitrogen and Oxygen) causing them to radiate light. This light creates the beautiful colours of the aurora!

The chemical composition of the ionosphere varies greatly with altitude and hence so does the colours produced by the incoming solar particles.
Winds blow through the ionosphere where the light emitting atoms are, causing them to shift in waves and ripples. The richly structured Auroral displays exhibit numerous shapes and forms such as bands, arcs, rays and sheets. No two auroral displays are alike and they may vary considerably in shape and brightness over timescales from seconds to minutes. For more technical information about Aurora go to: http://www.spaceacademy.net.au/env/terra/aurora/aurora.htm

Tankhouse looking West - Mawson