A first pan-Arctic assessment of the influence of glaciation, permafrost, topography and peatlands on northern hemisphere lake distribution

The locations of similar to 200 000 large northern hemisphere lakes (sized 0. 1 to 50 km(2), northwards of similar to 45 degrees N latitude) are intersected with new global databases on topography, permafrost, peatlands and LGM glaciation to identify some first-order controls on lake abundance and land area fraction at the pan-Arctic scale. Of the variables examined here, glaciation history and the presence of some form of permafrost appear most important to the existence of lakes. Lake densities and area fractions average similar to 300-350% greater in glaciated (versus unglaciated) terrain, and similar to 100-170% greater in permafrost-influenced (versus permafrost-free) terrain. The presence of peatlands is associated with additional similar to 40-80% increases in lake density and similar to 10-50% increases in area fraction. On average, lakes are 2 most abundant in glaciated, permafrost peatlands (similar to 14.4 lakes/1000 km(2)) and least abundant in unglaciated, permafrost-free terrain (similar to 1.2 lakes/1000 km(2)). Lake statistics are surprisingly similar across continuous, discontinuous and sporadic permafrost zones, decrease modestly in isolated permafrost, and drop sharply in the absence of permafrost. A simple calculation based on 'space-for-time' substitution for all glaciated/lowland terrain (similar to 2.7 x 107 km(2), of which similar to 48% is currently in some state of permafrost) suggests that in a 'permafrost-free' Arctic, the number of lakes could be reduced from similar to 192 000 to 103 000 (-46%) and their total inundation area reduced from similar to 560 000 to 325 000 km(2) (-42%). A more realistic scenario of thawed discontinuous, sporadic and isolated permafrost only, with a +10% lake increase in continuous permafrost and no change in permafrost-free areas suggests reductions to similar to 155000 lakes (-15%) and similar to 476 000 km(2) (-15%), respectively. Copyright (C) 2007 John Wiley & Sons, Ltd.