Climate Conditions at Perennially Ice-Covered Lake Untersee, East Antarctica

In November 2008 an automated meteorological station was established at Lake Untersee in East Antarctica, producing a 5-yr data record of meteorological conditions at the lake. This dataset includes five austral summer seasons composed of December, January, and February (DJF). The average solar flux at Lake Untersee for the four years with complete solar flux data is 99.2 +/- 0.6 W m(-2). The mean annual temperature at Lake Untersee was determined to be -10.6 degrees +/- 0.6 degrees C. The annual degree-days above freezing for the five years were 9.7, 37.7, 22.4, 7.0, and 48.8, respectively, with summer (DJF) accounting for virtually all of this. For these five summers the average DJF temperatures were -3.5 degrees, -1.9 degrees, -2.2 degrees, -2.6 degrees, and -2.5 degrees C. The maximum (minimum) temperatures were +5.3 degrees, +7.6 degrees, +5.7 degrees, +4.4 degrees, and +9.0 degrees C (-13.8 degrees, -12.8 degrees, -12.9 degrees, -13.5 degrees, and -12.1 degrees C). The average of the wind speed recorded was 5.4 m s(-1), the maximum was 35.7 m s(-1), and the average daily maximum was 15 m s(-1). The wind speed was higher in the winter, averaging 6.4 m s(-1). Summer winds averaged 4.7 m s(-1). The dominant wind direction for strong winds is from the south for all seasons, with a secondary source of strong winds in the summer from the east-northeast. Relative humidity averages 37%; however, high values will occur with an average period of ~10 days, providing a strong indicator of the quasi-periodic passage of storms across the site. Low summer temperatures and high wind speeds create conditions at the surface of the lake ice resulting in sublimation rather than melting as the main mass-loss process.