Some people think that the Arctic encompasses all the regions lying between the North Pole and latitude 66°33', called the "Arctic Polar Circle", which in principle delineates the territories where, in summer, the sun never sets.

Unlike the Antarctic, which is a landmass surrounded by an ocean, the Arctic is an ocean surrounded by land. It therefore consists of an enormous, essentially marine universe.

But such an approach is somewhat inaccurate. In fact the southern frontier of this geographical whole would appear to be more appropriately traced by the timberline, which, far from regular, fluctuates between 55° latitude North (in Labrador) and 71° latitude North (in Scandinavia).

The central part of this universe is permanently covered by ice. This is the polar pack. Around this, there is drift ice, then seas which, strewn with floating pieces, icebergs and numerous islands, finally open on to enormous emergent, non-floating expanses, whether insular (Greenland) or continental (Canada, Alaska, Siberia and Scandinavia). There one comes across the domain of the tundra, the last stage before the timberline and the subarctic lands of the taiga.

With an average thickness of three to five metres, the polar pack floats on an ocean that is at times reaches a depth of nearly 5,000 fathoms. It is as a result conveyed by the powerful transpolar drift current that flows along Northern Russia. Coming from the Bering Strait, this current carries the ice flow towards the north coast of Greenland, where it splits in two, one continuing along the east coast of this natural obstacle, the other heading off West to go and feed the circular Beaufort current that eddies at the heart of the Arctic Ocean.

The polar pack presents a surface of pressure ridges emanating from the meeting of separate ice-fields whose ends overlap to reach maximum heights of about ten metres. This type of event is however fairly infrequent because, on the one hand, of the meteorological calm that reigns at these latitudes and, on the other, of the thickness of the ice layer, which drastically limits the possibility of movement.

The drift ice
Unlike the polar pack, the drift ice is subjected to continuous displacement in wide portions of open sea. Currents, tides and winds exercise formidable constraints on it. All these pressures result from movements of compression and expansion that are not only embodied, at the sound level, by creaking, grunting and howling noises, but also, at the physical level, by crevasses, collisions and rafting. Some sheets crash together, are crushed and then disintegrate. Others override each other and overlap. This explains the chaotic look of the drift ice and the formation of hummocks, those mounds of ice that singularly complicate the task of travelling by sledge..

In winter, the ground seems to consist of a single block because the ice-fields are unified and monopolise the landscape for as far as the eye can see. Even if there are faults that occasion brutal encounters with salt water at -1.8°C with the air in the region of -40°C, this phenomenon seems both anecdotal and momentary: perhaps a long curtain of steam might possibly appear for something less than an hour, the time to allow the surface water to solidify once again.
But in spring, the spaces between the various ice-fields separate. When the temperature rises, the entire ice raft breaks up into pieces. At the beginning of May, the sheets draw apart allowing breaks to appear which, as they get bigger, are transformed into large fissures (channels), small turquoise-blue lakes or even, in some cases, immense open water lakes (polynyas).

Then the Arctic summer arrives. In this period that is characterised by the temperature stabilising between - 5°C and + 5°C and by the appearance of a thick layer of cloud covering the Arctic basin, the ice melts and breaks up even more. In a succession of movements that last until the autumn, the ice-fields are at times reduced to slabs of just a few square metres.

The Floes

Even at the very height of the "hot" season, the navigable water remains a long way away, in the vicinity of the continental coasts. Nevertheless, the ice raft's periphery is constantly changing. With the autumnal chilling, it can gain several kilometres in just a few hours. But during the summer, it loses a multitude of pieces of ice which break off and depart in the drift. This is the floating ice, also called floes, which are not to be confused with icebergs. .

The Icebergs

Unlike IIMs, which are flat and not too thick (3.6m at the very most), icebergs can reach a height of 100 metres. This difference is explained by their different genesis. Whereas the first originate from the polar pack, the second come from the lands that surround it, most frequently Greenland and Ellesmere Island. By way of example, Greenland's most prolific glacier, the Jakobshavn, generates 25,000 tons of ice per day.

Unlike IIMs, which are flat and not too thick (3.6m at the very most), icebergs can reach a height of 100 metres. This difference is explained by their different genesis. Whereas the first originate from the polar pack, the second come from the lands that surround it, most frequently Greenland and Ellesmere Island. By way of example, Greenland's most prolific glacier, the Jakobshavn, generates 25,000 tons of ice per day.

Only a part of an iceberg's total mass of remains above the surface. Between a ninth and a tenth, as the case may be. This variation depends on the characteristics of the glacier, with the more recent ones enclosing a distinctly greater quantity of air than the older ones, which, as a result, prove to be significantly heavier.

The Tundra

The circumference of the Arctic is made up of an immense plain, of which the north and south edges respectively correspond to the shore of the Arctic Ocean and to the tree line that is called the "timberline". This is the area of the tundra that covers the northern part of all the continents of the boreal hemisphere. Its overall surface area is estimated at 13 million square kilometres, or 1.1% of all emergent land.

A huge, white plain swept by violent squalls of freezing wind in winter, the tundra would be a complete desert if a layer of earth and impermeable, permanently frozen rock, the pergelisol (or permafrost), were not to allow the countryside to come back to life again during the summer by forcing the water to remain on the surface. During this warmer period, some regions give birth to a landscape comprising streams, rivers, ponds, lakes and peat bogs before being covered with flowers, plants and dwarf trees. Other, more arid, territories have to be content with sparse vegetation. .

The Timberline, entry to subarctic Taiga

The timberline snakes between 55° and 71° latitude North. Although its name suggests otherwise, it is less of a line than a transition area of which the width varies from a handful of kilometres to more than 160km from one region to another.

Compared with the tundra, the taiga is in effect characterised by distinctly longer and warmer summers, which manifestly allow the earth to thaw.

Transition? Yes. For this belt of stunted trees that stretches across prairies strewn with thickets and shrubs marks the frontier between the tundra and the other zone, the taiga, that takes us away from the Arctic territories themselves into the subarctic zone.
Compared with the tundra, the taiga is in effect characterised by distinctly longer and warmer summers, which manifestly allow the earth to thaw. As the permafrost is pushed far further down from the earth's crust (sometimes more than three metres) the trees can set down deep roots and grow distinctly to greater heights. Room, therefore, for conifers and even certain leafy trees, such as birch, which grow taller and taller the further south they are. This boreal forest covers half of Alaska, Canada, the Scandinavian countries and Russia.

The Ice Drift

The ice raft is not immobile. Under the effect of the wind, and 50 times slower, it drifts from 25' to 45' in relation to the direction of the air.
The wind, however, is not always in the game. When it is weak or inexistent, the ice cap moves only under the influence of the marine currents.
In which direction? To answer this question, there are several sources of information at our disposal - from wood which, coming from Asiatic rivers, is found along the shores of Greenland, to observations brought back from a good thirty or so Soviet expeditions, by way of information collected from the automatic Argos beacons and by analysis of satellite pictures.

So it is now known that the ice raft floats on water and that it is conveyed by the powerful transpolar drift current that comes from the Bering Strait, flows along Northern Russia and heads for the north coast of Greenland.
After passing this to the North and flowing along Ellesmere Island, this current is divided into two parts, the one coming in to lap the coast is from the "green land", and the other heading West and reaching the end of the Canadian archipelago (the Queen Elizabeth Archipelago) before joining the Beaufort Sea and feeding the circular current of the same name that eddies in a clockwise motion at the heart of the Arctic Ocean.
The current from the East of Greenland represents the most important exit from the Arctic basin because it allows the ice to go and melt in the subarctic seas, only a fraction hugging the coast to flow around Cape Farewell, to the South of Greenland, before returning along the Southwest part of that country.

For its part, the Beaufort current is active between the Canadian archipelago, Northern Alaska and the North Pole. As it circulates within a closed circuit, it traps the ice that has not drifted towards the West of Greenland. This is why the most ancient ice of the glacial Arctic Ocean is to be found at the centre of this current.