With the project now concluded and the scientists on their way home, Dr Petra Heil reflects on what the fast-ice team achieved.
Early this season Davis saw an influx of 12 sea-ice researchers/engineers to study various aspects of the near-shore fast ice, as supported by four complementary science projects. Land-fast sea ice is a pre-eminent feature of the near-shore zone, it is a sensitive indicator and modulator of Antarctic climate processes and is a structuring component of Antarctic marine ecosystems. Our projects are focussed on characterising the fast-ice, snow and ocean characteristics before and during the spring transition, and linking these to changes in the fast-ice associated algal biomass.
After a delayed arrival our team was quickly deployed thanks to favourable weather, speedy access to science cargo and early sea-ice training. The first snow cover data were collected on the day of arrival at the Davis fast-ice edge and the full deployment of the various projects followed on the fourth day after the RV Aurora Australis arrived in the harbour.
Since then we have had various sampling rounds, which vary from program to program. For example the sea-ice trace-metal biogeochemical team has three day cycles, and the fast-ice physics and ecosystems folk have four day cycles, which include about two full days on the fast ice, followed by laboratory analysis of the samples. The weather and some broken gear slowed some work, but with the support of an incredibly skilled and enthusiastic station support team most of our work moved on well.
Overall the fast-ice physics and ecosystems team (five scientists supported by one engineer) has worked on four transects. At each of these a Remotely Operated Vehicle (ROV; equipped with a radiometer, cameras and upward looking sonar to detect ice draft) flew in the ocean underneath the fast ice along a 128 m transect, as well as covering a 32 m x 32 m box. Coincident snow-thickness and ice-surface temperature measurements were taken along the transect before a second radiometer was deployed directly underneath the ice through a core hole.
Up to 12 ice samples were also taken along the transect to determine the algal biomass within the fast ice. A detailed examination of the snow cover was made in dedicated snow pits at 0 m, 128 m and 512 m along the transect.
At the same locations three ice cores were retrieved to derive vertical profiles of ice temperatures, salinity, density, structure and isotope composition. Detailed analysis of snow, ice and water samples were then undertaken back in the science laboratory or sea-ice freezer laboratory (at −22°C). Some samples will be sent to Australia for further analysis. Complementing the survey are intensive snow-thickness measurements over the wider area, which are referenced to the ice surface by internal GPS.
As part of an over-winter project (ably handled by the wintering science engineer and supported by the wintering team) a pair of sea-ice mass-balance stations have been recording vertical profiles of ice and snow temperatures (at 2 cm intervals) as well as the near-surface ocean and atmosphere. To merge these observations in with seasonal changes in the oceanic mixed layer, vertical profiles of the ocean properties were collected at the transect site as well as next to the over-winter ice mass-balance site.
These activities form only a component of the overall sea-ice research carried out off Davis station this spring. There are a number of other research projects going on this spring and summer and the station has been incredibly busy supporting us in addition to their regular maintenance and infrastructure workload. Thanks for having us at Davis.
Sea ice physicist