ANOTHER LIFE: THOSE CRYSTALLINE DAYS after Christmas conjured a strange magic as the sun went down. We are used to grand theatre in the ocean's winter sunsets - vast, baroque spectacles of crimson, gold and purple clouds. But in that uncannily pristine air, clear right to a razor-sharp horizon, the afterglow when the sun went down made a rainbow's prism of the sky, writes Michael Viney
I had a schoolroom mnemonic - ROYGBIV - for the sequence of a rainbow's colours and there, indeed, were the upwardly merging bands of red, orange, yellow, green, blue, indigo and violet, the last a high shadow pinned like a brooch with Venus, the glittering evening star.
A phenomenon of dense polar air trapped beneath a warmer layer, I am told it was a sight to treasure, along with the famous "green flash" I once saw at sunset - another rare gift of refraction and atmospheric chance. But today, as I write, we're back to clouds - low, murky coils of dark grey stuff, uncertain whether to be mist or nimbostratus, waiting to unload some drizzle as the high-pressure zone drifts east.
As the world warms up, everything about clouds presses for investigation: they regulate so much of our climate and weather. Cooling Earth by bouncing sunlight back into space, yet helping to trap the heat that does get through, they offer the biggest uncertainties in modelling the future of climate change.
Most of us know something about how they form: the cooling of warm, humid air as it rises, its moisture condensing into billions of water droplets that, colliding and fattening and gaining in weight, may eventually fall as rain. Also, maybe, how each droplet needs a nucleus to build on - an airborne particle, or aerosol.
Satellites above the ocean film thin white lines of low cloud trailing after ships as their smokestacks belch sulphur dioxide into the sky. But particles from man-made pollution can be crude in size compared with those that nature makes by clustering molecules of organic vapours.
Over forests, for example, clouds can build from particles formed from terpene gases released from the canopy. The critical embryo is a cluster of molecules about one nanometre in size - one millionth of a millimetre.
Since 70 per cent of the Earth is ocean, the systems of marine aerosols are vital to understanding cloud formation, and Irish scientists are, so to speak, surfing new waves of discovery, notably those breaking around Mace Head, a bare and boggy headland near Carna, on the other side of Connemara.
Here are laboratories run by NUI Galway, built at the site of an old look-out post uniquely open to pristine winds and sea. Marine aerosols have been measured there for 50 years, on and off, but Mace Head is now a key resource in the eastern Atlantic for the scientists of Global Atmosphere Watch. A spur to its development was the independent, pioneering research carried out by Britain's James Lovelock, founder of Gaia theory, at his holiday cottage at Adrigole in west Cork, in the 1960s and 1970s. Mace Head's presiding genius today is Galway's Prof Colin O'Dowd, a prizewinning figure in aerosol science. He led a 10-strong team of European scientists in work that has changed the picture of the particles offered by the ocean to the sky.
Along with sea-salt particles whipped up from spray, it was widely thought, but hard to prove, that sulphate produced by algae, including the great blooms of oceanic plant plankton, was the chief source of the particles needed for cloud condensation. But Dr O'Dowd and his team discovered another vital ingredient in new particles - iodine vapour from coastal seaweed exposed to the sun at low tide. Over "hot spots" of Connemara's thick fringes of bladderwrack, aerosol nucleii reached peak concentrations of up to one million per cubic centimetre, produced for hours on end. Most were shared between iodine and sulphate, but some were made of iodine alone.
These coastal "particle bursts" are thought to be much more frequent and intense than anything happening out at sea, but modelling by the O'Dowd team suggests iodine would have to come from somewhere in the open ocean. Indeed, in the next issue of Environmental Chemistry, Dr Alex Baker of the University of East Anglia will show, from extensive Atlantic cruises, that organic forms of iodine are "widespread and abundant in aerosol particles in the broader marine atmosphere". All this calls to mind the local era here in Mayo when kelp was burned in stone ovens on the shore to provide raw material for iodine extraction. Great plumes of black smoke carried the smell far inland on the wind; whether or not they made clouds is not on record.
Coastal seaweeds of all kinds are now earmarked for new developments in foodstuffs, pharmaceuticals, even biofuel. In fixing sustainable harvests, we may need to leave a share for the sky.
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Ireland's Ocean: A Natural Historyby Michael and Ethna Viney is published by the Collins Press, Cork
EYEONNATURE
We have nightly visits to our garden from our local foxes. We put cat flaps in our garden gate and shed to provide shelter for cats locked out at night. Recently, after a severe overnight frost, I went to the shed and found a large fox comfortably curled up in the cat box. It briefly raised its head and looked at me, as if to say "close the bloody door", and settled down again, so I beat a hasty retreat.
Liam O'Riordan,
Monkstown, Co Dublin
While waiting for the Dart at Booterstown station, I spotted a little egret, a godwit, a pair of teal, a moorhen, two blackheaded gulls, a flock of brent geese and, to top it all, a flash of cobalt as a kingfisher flew up the small channel at the side of the marsh. I am so lucky to have this treasure on my doorstep.
Frances O'Sullivan,
Booterstown, Co Dublin
Recently a blackcap turned up in the garden. Long-tailed tits have become common in the garden, displaced I think by building in the area.
Green finches and siskins seem to have become less common. And I photographed a flock of 60-plus goldfinches flying silhouetted against Howth Head.
Tony Dolan, Swords, Co Dublin
Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo; e-mail: viney@anu.ie. Please include a postal address.