Based on data from low elevation lake sites, previous studies have suggested three quantitative relationships related to summer (December, January and February) air temperatures in the Dry Valleys of Antarctica: i) decrease with altitude at the dry lapse rate of 9.8°C km-1, ii) increase with distance from the coast at a rate of 0.09°C km-1, and iii) degree-days above freezing during the summer months is logarithmically proportional to the maximum summer air temperature. Here, we tested the first two of these rules at high elevation sites in Upper Wright Valley. Direct measurements confirmed that the summer lapse rate followed the dry lapse rate. For the three furthest stations, Tyrol Valley, Mount Fleming and Horseshoe Crater, the average difference between the measurements and the predicted summer monthly averages are -2.1±1.4°C, -0.5±1.0°C and -0.4±0.9°C, respectively. By contrast, at Linnaeus Terrace (54 km from the coast) the monthly average is warmer than predicted by several degrees: +4.3±1.3°C. The inland temperature gradient at these high elevation sites may result from sunlight effects rather than coastal wind as previously shown for the lower valleys. The warm conditions observed c. 50 km from the coast may reflect a zone affected by both sunlight and coastal wind.

This study investigates the microclimate and hydrology of debris-laden ice surfaces in the Taylor Valley, Antarctica, in early summer, focusing on the onset of melt. Measurements of energy and mass fluxes were made on an outwash fan and in moraines near the terminus of Taylor Glacier. The surface microclimate was strongly controlled by absorbed solar radiation, with a low albedo of 0.17. Seasonal warming of the substrate led to an abrupt shift in thermal and hydrological patterns as temperatures exceeded freezing point. Within a week the Bowen ratio switched from 2.05 to 0.48 and mass losses to the atmosphere increased four-fold from 0.39 to 1.6 mm d-1. Melt onset also produced complex ground temperature patterns with strong diurnal damping below the freezing front. These patterns were caused by phase changes in the freezing front, coupled with an abundant water supply from local runoff. Of secondary importance to the surface energy balance and mass fluxes was the effect of local winds on boundary layer characteristics. This resulted in larger mass losses during the more turbulent, warmer and drier down-valley flows.