[1] Climate observations from the McMurdo dry valleys, East Antarctica are presented from a network of seven valley floor automatic meteorological stations during the period 1986 to 2000. Mean annual temperatures ranged from À14.8°C to À30.0°C, depending on the site and period of measurement. Mean annual relative humidity is generally highest near the coast. Mean annual wind speed increases with proximity to the polar plateau. Siteto-site variation in mean annual solar flux and PAR is due to exposure of each station and changes over time are likely related to changes in cloudiness. During the nonsummer months, strong katabatic winds are frequent at some sites and infrequent at others, creating large variation in mean annual temperature owing to the warming effect of the winds. Katabatic wind exposure appears to be controlled to a large degree by the presence of colder air in the region that collects at low points and keeps the warm less dense katabatic flow from the ground. The strong influence of katabatic winds makes prediction of relative mean annual temperature based on geographical position (elevation and distance from the coast) alone, not possible. During the summer months, onshore winds dominate and warm as they progress through the valleys creating a strong linear relationship (r 2 = 0.992) of increasing potential temperature with distance from the coast (0.09°C km À1 ). In contrast to mean annual temperature, summer temperature lends itself quite well to model predictions, and is used to construct a statistical model for predicting summer dry valley temperatures at unmonitored sites.

No abstract

No abstract

Salinity increased from 48 to 93 g/l total dissolved solids (TDS) in Mono Lake, California between 1941 and 1982, and is expected to fluctuate between 169 and 248 g/l at equilibrium by the middle of the next century. In order to predict the consequences of this trend on the Mono Lake ecosystem, we determined effects of salinity on survival, growth, reproduction and hatching ofArtemia monica, Mono Lake's only macrozooplankton species. Seven salainities ranging from 76 to 179 g/l were tested in a long-term experiment to determine both lethal and sublethal responses. The salt tolerance limit for subadultA. monica was between 159 and 179 g/l. Adult size, growth rates, and brood sizes decreased, and female mortality during reproduction increased, as salinity increased. Hatching of diapause eggs was delayed and total percent hatch decreased as salinity increased, and hatching failed at 159 g/l. The life-time reproductive potential of individual females decreased linearly over the seven salinities tested. Based on this study, we predict a decrease in the productivity of theA. monica population in Mono Lake and extinction of the species is probable before the lake reaches equilibrium.

ABSTRACT. The surface energy bal ance was calcul ated to estimate sublim ati on and melt on the surface a nd terminus of Canada Glacier, Taylor Vall ey, Antarctica, during the 1 994~95 a nd 1 995~96 austral summers. Our resul ts indicate th at sublimati on accounted for roughly 80 % of the obse rved 1 994~95 summ er a bl ation a nd 40 % of the obse rved 1 995~96 summer ablati on on the surface of the glacier. Sublim ation on the termi nus cl iffs appears to be less significant tha n sublimation on the glacier surface, probably acco un ting for at most 1O~ 15% of the measured ablation. Based on th ese results, both surface a nd terminus cliff melt we re calculated and compa red with gauged flow in the glacial streams. "Ve fo und tha t while the terminus cliffs represent onl y 2% of the total ablation zone, they acco un t for 10~4 0 % of the total meltwater r unoff. G ive n our current instrumentation, we can estima te meltwater discha rge from the glacier with a n accuracy of ±20%.