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The Aurora Australis continues its journey across the Southern Ocean on an East by North East heading, making good progress in moderate, following seas. By day the vessel is surrounded by a myriad of sea birds, with some groups - like the petrels clearly dominant among the total number of species sighted, and showing considerable variation in size and colour within that group. Petrels and their relatives have escorted the Aurora throughout the voyage, from the more common short-tailed shearwaters found commonly around the coastal areas of Tasmania, to their smaller, more specialised cousins feeding within the ice fields off Antarctica, and returning to nest amongst the peaks of the few exposed ranges dotting the coastline including those nunataks found around Mawson station.
Some of the petrels found in this central section of the Southern Ocean, where the vessel is roughly halfway between Tasmania to the East and the remote Kergulen, Heard and McDonald islands to our West appear identical to one another until they draw close enough to expose subtle differences. Black or white bellies, eye rings, mottling or even slight variations in wing shape. These smaller seabirds are difficult photographic subjects at the best of times, their hunting habits seeing them dart between the waves and rarely visible from the same angles for long. A few of the expeditioners, who come to the voyage prepared with professional grade cameras and lenses, may have more luck – but it still takes considerable patience standing in the right position on the exposed upper decks, to secure a perfect shot.
Another notoriously difficult but highly sought after subject for the photographers aboard - professional and amateur alike - is the almost nightly spectacle of the Southern Lights, or the aurora australis. To ensure the summary provided in the following explanation of the aurora is technically accurate, the author credits the 'Mariner's Handbook' of the UK Admiralty's Hydrographic Office.
'Aurora means dawn. The light of the aurora is emitted by atmospheric gases when they are bombarded by a stream of electrically charged particles originating from the solar flares of the sun. As the stream of particles approaches the earth they are directed towards the two magnetic poles by the earth's magnetic field, so entering the atmosphere [and causing the aurora] within the higher latitudes of each hemisphere. The aurora in the Northern hemisphere is known as aurora borealis. The emission of light that is seen as the aurora occurs at heights above 60 miles, so that it may be seen at distances of up to 600 miles from the place where it occurs overhead.
Much of the Southern auroral zone occurs within the boundaries of the Antarctic continent, also extending into the adjacent oceans passing near Macquarie Island [the location of another Australian station also the only station within sub-Antarctic regions], at the approximate latitude of 60 degrees South [This is why, during particularly strong auroral events, the light of the aurora Australis can be clearly seen from mainland Tasmania (and periodically even as far as Southern Victoria].'
This evening, as this report is being written, the faint beginnings of an aurora are already visible towards the South East, appearing as a long, faint ribbon of green-white light extending upwards from the horizon. Depending on other light sources, such as the moon these auroral displays can vary in their intensity and colour, some presenting so strongly in the night sky that their light can still be captured even with basic photographic equipment from the upper decks of the vessel. So far this voyage, the best auroras have been sighted from around 11pm, meaning not all expeditioners are aware or even awake to witness them. Expeditioners present within Antarctica often have the best seats to take in the dance of light and colour that is the aurora Australis, with some of their footage providing a visually stunning record of the aurora's strength in the far South. Most of the characteristic curves, waves and curtains of light associated with the aurora's displays form and dissipate just too slowly for the naked eye to pick up as distinct movement but observing them for between 10 to 30 minutes or more changes in these patterns are clearly noticeable.
Provided the clear skies continue, it's likely that the crew and expeditioners aboard will have several more opportunities to take in the Southern Lights, while we're still many hundreds of miles from any man-made light sources which would otherwise diminish the impact of this phenomenon's display.
Cheers
Mark & Fred
Map
A map showing Australia and Antarctica. The map shows the journey of one voyage that has occured in the season, with each route highlighted in a distinct colour.