Influence of air temperature on a glacier's active-layer temperature

Abstract

Seasonal temperature variations occur in the glacier layer about 15-20 m below the surface, while at greater depths the glacier temperature depends on the long-term surface conditions. It is generally accepted that for glaciers without surface melting the temperature at 10 m depth (T10) is close to the mean annual air temperature at standard screen level (Ta), i.e. T10 = Ta. We found that this telationship is not valid for Ta above -1 7°C and below -55°C. The goal of our investigation is to find a better temperature transfer function (TTF) between Ta and temperature at the boundary of the active layer in accumulation areas of polar and tropical glaciers. Low-precision T10 temperatures from boreholes, obtained at 41 sites, are compared with air temperatures (Ta) measured in the vicinity of these sites for at least a 1 year period. We determine that when Ta falls into the temperature range -60 to -7°C, empirical values can be approximated as T10 = 1.2 Ta + 6.7. Analysis of these data suggests that high T10 occurs in the areas of the glacier that collect meltwater.