The end of the Arctic as we know it?

Another Life:  Three summer months in the High Arctic almost 20 years ago doesn't exactly rate for the Explorers Club, but my one big outdoors adventure left a small proxy of my soul among the life at the top of the Earth.

An autumn hint of green in the Atlantic sky has had me checking on the internet for the weather in north-east Greenland, and feeling quite relieved to learn of "light snow" in the mountain wilderness of Germania Land. I can imagine the huge silence enfolding the fiord of Klaegbugt as dusk swoops in around 2pm; even the sea sounds are stilled by new ice.

This is how it should be in October. But the climate change enveloping the Arctic at large is drastic and disquieting. The area of summer sea ice this September was the lowest in Nasa's satellite records and some models show it almost disappearing by the end of the century. This will reduce the reflectivity (albedo) of the ocean surface and so increase the rate of warming even further. On land, the snow is already melting earlier in spring and arriving later in autumn, and the darker surface of a longer summer soaks up more heat again.

The maximum summer melt of the Greenland ice sheet has increased in 25 years by an area the size of Sweden. The great pulse of meltwater that flowed into our fiord in June, surging out in waterfalls from the rim of the barren cliffs and roaring down the valley in silt-laden waves, will begin weeks earlier and last even longer as the thaw reaches further up the mountains. All this, of course, also has ominous implications for Ireland's winter warmth, as fresh water floods into the ocean and slows the northward roll of the Gulf Stream in the North Atlantic Current.

It also has some implications for Ireland's winter geese, now arriving back from the Arctic by way of Iceland. The Germania Land expedition, with David Cabot and Roger Goodwillie, was to ring as many barnacle geese as we could catch, hoping that birds that winter on Co Mayo's Inishkea Islands would be among them. They were nesting on ledges high on the cliffs, safe from predators. Once the chicks had jumped to join their parents on the scree below, the families set off across the tundra on foot, dodging Arctic foxes, to take refuge in the middle of the nearest lake.

What could change about that? First, the vegetation, as the tundra's prostrate willows, and low flowering plants give way to tall, dense shrubs and even birch and spruce. And then the lake may not be there: thousands of Arctic lakes are disappearing, as soil made solid by permafrost thaws out and the water soaks away.

Other Irish geese - the brents, for example, now assembling at Strangford Lough, Co Down, and the Greenland white-fronted geese on their way to the Wexford Slobs - and many of our winter waders nest on low-lying islands and coastal fringes of tundra. Even if they escape the rise in sea level, the new, shrubby vegetation will close out the early view of predators.

I think also of a little herd of musk oxen we watched across the valley. They formed a ring, sharp horns lowered and pointing outwards, to face down a menacing grey wolf. In such an open landscape, they could spot their enemy coming: in a valley of dark spruce, how much more vulnerable they will be (and how impossibly hot in that great coat of winter wool).

Adapted to tundra and polar desert, the loss of the musk ox would be a sad redundancy.

The polar bear is even more specialised, depending on sea ice for mobility and a supply of seals for food. Pregnant females build their winter dens in thick snow and emerge, fat reserves exhausted, to teach their cubs to hunt in spring. The dwindling of ice floes, their earlier break-up and later formation, all threaten the bears' condition and reproductive success.

Fewer, smaller cubs are less likely to survive. The whole species, indeed, may be reduced to a few dispirited relics pacing the concrete bergs in zoos.

Three kinds of seal - ringed, ribbon and bearded - also rely on the ice, where they give birth and rear their young. The walrus, too, floats on the floes and dives to rake up shellfish with its tusks. An iceless Arctic Ocean will reduce its feeding area and give it nowhere to rest.

A warmed-over Arctic could, of course, be good for global business, opening up new mines, oil wells and forests and new polar routes for shipping. It could improve conditions for cod and herring. It would even provide more living-space for migrant humans if - like the patient Inuit peoples - they could get used to a couple of months in the dark. But we need the Arctic as it still remains, a bleakly beautiful arena where nature rules and humans play out their trials and dreams.