Numerical simulations of wind and temperature structure within an Alpine lake basin, Lake Tekapo, New Zealand

High-resolution numerical model simulations have been used to study the local and mesoscale thermal circulations in an Alpine lake basin. The lake (87 km(2)) is situated in the Southern Alps, New Zealand and is located in a glacially excavated rock basin surrounded by mountain ranges that reach 3000 m in height. The mesoscale model used (RAMS) is a three-dimensional non-hydrostatic model with a level 2.5 turbulence closure scheme. The model demonstrates that thermal forcing at local (within the basin) and regional (coast-to-basin inflow) scales drive the observed boundary-layer airflow in the lake basin during clear anticyclonic summertime conditions. The results show that the lake can modify (perturb) both the local and regional wind systems. Following sunrise, local thermal circulations dominate, including a lake breeze component that becomes embedded within the background valley wind system. This results in a more divergent flow in the basin extending across the lake shoreline. However, a closed lake breeze circulation is neither observed nor modelled. Modelling results indicate that in the latter part of the day when the mesoscale (coast-to-basin) inflow occurs, the relatively cold pool of lake air in the basin can cause the intrusion to decouple from the surface. Measured data provide qualitative and quantitative support for the model results.

Window, Lake Weyba House, Sunshine Coast

Vinyl window to daybed alcove, bedroom pavilion, South-West elevation.

Window, Lake Weyba House, Sunshine Coast

Vinyl window to bath house pavilion, South-West elevation.

Main Pavilion, Lake Weyba House, Sunshine Coast

As seen from West, looking towards front of main pavilion. Standard roller doors to clerestory.

Pivoting vent, Lake Weyba House, Sunshine Coast

Bedroom pavilion, South-East elevation. Day bed alcove on left.

Pavilions and outdoor seating area, Lake Weyba House, Sunshine Coast

As seen from back of bedroom pavilion, looking towards main pavilion. Day bed alcove to bedroom in foreground.

South-West elevation, Lake Weyba House, Sunshine Coast

Bath house and bedroom pavilions, with outdoor seating area in foreground.

Main pavilion, Lake Weyba House, Sunshine Coast

South-West elevation of main pavilion - living, kitchen, dining and study/guest areas.

Bedroom pavilion, Lake Weyba House, Sunshine Coast

As seen from outdoor seating area. Pivoting vent on left and day bed alcove on right. Standard roller doors to clerestory.

Bath house pavilion, Lake Weyba House, Sunshine Coast

South-West elevation. Paved seating area in foreground.

Bath house pavilion, Lake Weyba House, Sunshine Coast

Link to bedroom pavilion on right; roof of main pavilion on left.

North-East elevation, Lake Weyba House, Sunshine Coast

Bedroom pavilion on left, bath house pavilion centre and main pavilion on right.

North-East elevation, Lake Weyba House, Sunshine Coast

As seen from East, looking along pavilions. Bedroom pavilion and day bed alcove in foreground.

Distribution of major, minor, and trace metals in lake environments of Antarctica

The concentrations of major, minor and trace metals were measured in water samples collected from five shallow Antarctic lakes (Carezza, Edmonson Point (No 14 and 15a), Inexpressible Island and Tarn Flat) found in Terra Nova Bay (northern Victoria Land, Antarctica) during the Italian Expeditions of 1993-2001. The total concentrations of a large suite of elements (Al, As, Ba, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Gd, K, La, Li, Mg, Mn, Mo, Na, Nd, Ni, Pb, Pr, Rb, Sc, Si, Sr, Ta, Ti, U, V, Y, W, Zn and Zr) were determined using spectroscopic techniques (ICP-AES, GF-AAS and ICP-MS). The results are similar to those obtained for the freshwater lakes of the Larsemann Hills, East Antarctica, and for the McMurdo Dry Valleys. Principal Component Analysis (PCA) and Cluster Analysis (CA) were performed to identify groups of samples with similar characteristics and to find correlations between the variables. The variability observed within the water samples is closely connected to the sea spray input; hence, it is primarily a consequence of geographical and meteorological factors, such as distance from the ocean and time of year. The trace element levels, in particular those of heavy metals, are very low, suggesting an origin from natural sources rather than from anthropogenic contamination.