3.1.4.1, 3.1.4.2 - Cold environments and glacial systems

Cold environments in space and time

Cold environments occur at high latitudes and at high elevations because the energy available to warm the surface is limited. Polar regions receive low-angle sunlight and have long winter nights; alpine environments become colder with increasing altitude. Maritime settings may receive abundant snow, whereas continental polar interiors can be very dry. Cold does not mean that every place has identical precipitation or vegetation.

Today Greenland and Antarctica contain large ice sheets; smaller ice caps and valley glaciers occur in places such as Iceland, Alaska, the Alps, the Andes and the Himalaya. Ice can exist at tropical latitudes on sufficiently high mountains. Arctic tundra and high mountain ground provide extensive periglacial environments, although not every seasonally frozen site has permafrost. Polar describes latitude, alpine describes elevation and relief, and glacial describes the presence of land ice: these categories overlap rather than exclude one another.

During the Pleistocene, approximately 2.58 million to 11,700 years ago, repeated cold stages extended ice sheets across much of northern North America and northern Europe, including much of Britain. Mountain glaciers expanded in ranges such as the Alps and Andes. Around these ice margins, and farther south in unglaciated lowlands, colder conditions produced periglacial features. Present polar ice is therefore only part of the area with a glacial inheritance. Yosemite in California and Cwm Idwal in Wales contain relict landforms left by larger former glaciers, while southeast Vatnajökull in Iceland has active outlets. A glaciated landscape can remain after its glacier disappears; a U-shaped valley is not evidence of ice flowing there today.

Climate, soils and vegetation interact

Low temperatures constrain biological activity and change drainage, so climate affects both soil formation and vegetation. Short growing seasons favour low, hardy plants in tundra and alpine settings. Mosses, lichens and dwarf shrubs can survive conditions that limit trees, but Antarctic ice-covered interiors support very little terrestrial vegetation. Wind exposure, snow cover, slope and available moisture create contrasts within the same region.

Cold slows decomposition and nutrient release. Organic matter may accumulate where wet soils restrict oxygen, while thin soils develop where frost-shattered rock is exposed and plant colonisation is slow. On thawing ground above impermeable ice-rich permafrost, meltwater can collect in the active layer, causing summer saturation even where precipitation is low. A drained gravel ridge nearby may remain much drier. Soil conditions therefore cannot be inferred from air temperature alone.