Firn-Ice Transition at MES and WHG

Density measurements on the recovered cores show the depth of bubble close off is reached at MES at about 60m depth while at WHG the firn- ice transition lies below the recovered 100m depth. This underpins the unique characteristics of the MES core. Currently, only the Australian Law Dome ice core has an similar shallow bubble close off depth. Once the annual snow accumulation for the site as been calculated, we can determine whether MES is also as rapid or potentially even faster than at Law Dome, providing the opportunity to measure an extremely high resolution greenhouse gas record.

Fig. 15: Density measurements on MES (blue) and WHG (pink) ice cores.

Automatic Weather Station Data from EPG

The weather station continuously recorded data since our last visit on 01 December 2005 until 04 Jan 2007, when we visited the station to download the data and for maintenance work. The recorded data for pressure, solar irradiation, air temperature, snow temperature, dew point, and snow accumulation are shown in below (Fig.16).

Fig. 16: EPG automatic weather station data for 01 Dec 2005 to 04 Jan 2007

As shown in Fig.16 temperature tracks overall solar irradiance. However, from May until early October abrupt temperature increases of up to 20K occurred. Some of these temperature excursions are accompanied by changes in barometric pressure suggesting that these warm events could be katabatic outflow from the McKay Glacier portal. Temperatures in the snow pack measured concurrently at 16 depth horizons from 0.135m (light blue) to 2.085m (red) show the decreasing influence of air temperature variability with depth. The snow temperatures have yet to be corrected for their change in depth, which increased by 60cm as shown in the snow accumulation graph below. The snow accumulation record shows that most of the precipitation occurred during six events of 5 to 10cm snow accumulation. The data show also that are no prolonged time periods of snow loss, except in the first 2-5 days after the snow precipitation page 13 event which is partly due to snow compaction. After this time period the snow surface remains stable. Overall, the data confirm EPG as an excellent ice core site. The snow pit data and submergence velocity measurements from EPG and VLG have yet to be processed.