Aim of the work

Since 1996/97, IMAU (the Institute for Marine and Atmospheric Research at Utrecht University) has operated Automatic Weather Stations (AWS) at 10 different sites. In the course of the years, six have been removed after several years of data collection; the remaining four AWS will be retained at so called key-locations for longer term monitoring. Two remaining AWS are located close to Wasa (AWS 5) and Svea (AWS 6), and have been in operation since the 1997/98 field season. Another AWS is situated close to the deep drilling at Thyssen Höhe, Berkner Island, by the British Antarctic Survey, and the last AWS is situated close to the German station Kohnen on Amundsenisen, where the EPICA deep drilling operation is ongoing. The coordinates and elevation of the four AWS in Dronning Maud Land, Antarctica, are given in table 1.

Apart from providing basic climate information like air pressure, temperature, relative humidity, wind speed and direction, the AWS are equipped with sensors measuring snow temperatures at several depths, atmospheric radiation components and height of the snow surface. Including these sensors offers the possibility to make a full energy balance calculation from the AWS data. The data of snow height are used to detect precipitation events in support of the interpretation of ice core data. In conjunction with this, regular sampling is done of the snow under the AWS height meter for water isotope analysis

Field work in 2002/03

In the field season 2002/03, AWS 5 near Wasa and AWS 6 near Svea were serviced by personnel of the Swedish Polar Research Secretariat. The servicing included the tedious job of digging out the stations and raising them to the original level above the surface; futhermore, memory modules were exchanged and software updated. Before this was done, last year’s snow was sampled at the AWS sites for laboratory analysis. Unfortunately those samples were lost in the freezing facility in Cape Town, but were recovered in October 2003, still in frozen condition. Another important task performed in the 2003 field season was the removal of AWS 4 from Riisen Larsen Ice Shelf and AWS 7 from the blue ice of Scharffenbergbotnen. These AWS had also been in operation since 1997/98.

Preliminary results

The good reliability of the equipment in combination with the ARGOS transmission of the data to Utrecht and yearly servicing has led to data series almost without gaps, quite a unique feature for Antarctic AWS. Especially the accumulation data of the height sensor and the radiation data are of great scientific value, since little is known about precipitation variability and radiation balance in Antarctica. As an example, Figure 2 shows four years of accumulation data at AWS 4, 5, 6 and 9. As can be seen, accumulation is much more frequent at AWS 4 than at AWS 5 and 6, where much of the annual precipitation falls in a couple of well-defined events. Surprisingly, accumulation is greater at inland AWS 6 than at coastal AWS 5, probably because AWS 6 is situated at the foot of the steep Heimefrontfjella, which forces orographic precipitation. Also note the substantial amounts of snow being removed from the surface by summer sublimation.

Under certain conditions, the AWS data are available free of charge. Those interested to work with the AWS data should contact Michiel van den Broeke or Carleen Reijmer.