High resolution studies of cosmogenic beryllium isotopes (7Be) at Law Dome

Full description

Energy from the Sun drives the Earth's climate system but this energy varies: there is an 11 year solar cycle and the Sun's intensity has varied over longer timescales. Reconstructing how the Sun's output has varied in past times is crucial to understanding the Earth's past climate which is key to predicting future climate change. Naturally-occurring radioactive isotopes such as 7Be and 10Be are produced in the Earth's atmosphere by cosmic rays, at a rate controlled by the activity of the Sun, and are layered in ice sheets, thus providing a means of reconstructing past solar output.

A ~1.4 x 1 x 1 m pit was dug on Law Dome. The wall was flattened using a ~60 cm level, handsaw and paint scrappers. A significant sastrugi could be seen in the top right of the wall. Sampling was started on the left of the wall to avoid this where possible. Wearing plastic gloves to avoid contaminating the samples, the top surface was levelled to the lowest point, and some of the snow collected as sample P1-1. It was around 4 cm at its highest point. A 10 cm x 10 cm grid was drawn into the wall, covering 80 cm x 80 cm. The top 10 cm layer was sawn out of the wall using a hand saw, cutting into the wall by at least 20 cm along the horizontal 10 cm below the top surface, then the back 20 cm from the front surface, and finally chopping the large block into smaller blocks.

The extra six blocks were discarded, and the two samples were put into zip lock bags as P2-1 and P2-2. The back of the sampling area was cleared back to allow easier access for the next layer. This was repeated for seven more layers, finishing with P9.

One block from each level was used for density measurements. The samples from each level were combined into a melting jar and carrier added. For some samples, not all the blocks fitted at once, so a portion of the blocks were melted (with the carrier) in the oven at 60 degrees C. The samples were allowed melt completely overnight. ~10mL of the samples were retained for water isotopes . The samples were filtered though 41 microns and the 0.45 microns and pumped onto cation columns.

Lineage

Progress Code: completed