Sea-ice and snow characterisation

 

Petra Heil, Adam Steer, Rob Massom, Roger Stevens, Jennifer Hutchings and many volunteers

Sea ice is highly variable at many temporal and spatial scales. Whilst in general sea-ice physicists are looking to detect changes at the regional scale, local-scale observations are necessary to provide information on the inherent fine-scale variability in ice-thickness distribution. This data is crucial to investigate ice redistribution, to estimate the ice-mass balance, and to validate remote sensing observation techniques (including laser altimetry). Local-scale data are also used to provide verification of numerical sea-ice models. Due to the lack of remote observational techniques, there are generally few direct measurements of  ice-thickness in the Antarctic sea-ice zone. During this cruise we will collect in situ data along transect lines to provide the physical characterisation of sea ice at the scale of individual ice floes.

At a typical ice station, we will make observations of sea-ice and snow thickness as well as freeboard height and the distribution of surface flooding. The snow-ice interface temperature and near-surface air temperature will also be measured using of snow probes and measurements through drill holes. These observations will be carried out every metre along two intersecting 100 – 200m transects, in order to resolve the typical length-scale in the surface variability of the ice floe.

There will also be more detailed measurements of ice and snow properties at greater spacing. We will recover full thickness sea-ice cores every 50m along these transects as well as nearby interesting ice-floe topography. The vertical ice-temperature profile will be measured immediately after recovery of each core, before the core is taken to the ship-board freezer laboratory for further analysis. In addition, snow pits will be dug and analyzed at this spatial scale.