World-Wide Variations in the Direction and Concentration of Cirque and Glacier Aspects

ABSTRACT

Topoclimatic effects on glacier balance encourage shade, lee and east-facing glaciers in varying combination in different regional climates and at different altitudes. Present-day glaciers usually face slightly east of poleward on average: in Scandinavia and the Urals, consistent westerly winds strengthen the lee tendency, especially where gentle summits favour drifting of snow. Eastward cirque aspects are found in the Falkland Islands, New Hampshire and Central Spain, east-northeast aspects in the American Rockies, the Faeroes, Central Europe, Japan and Tasmania. In Scandinavia, the British Isles and the Carpathians, northeastward resultants are most common, showing a lee effect tempered with a shade effect. Elsewhere (in the Canadian Arctic, Alaska, British Columbia, western U.S.A., central Chile, the Alps, southwest and central Asia, the Altai and even Papua—New Guinea), both cirque and glacier aspect resultants are poleward or within 30° further east. This situation reflects differential ablation from direct solar radiation as a more important factor than wind. Cirque aspects provide a constraint on palaeoclimatic reconstructions but cannot provide precise information on palaeowind directions.

The degree of asymmetry (vector strength) varies more locally and is usually greater in ranges which were only just high enough to nourish glaciers. For a temporal comparison of glaciers with cirques, this observation may be formalised as a “law of decreasing glacial asymmetry with increasing glacier cover”.