The surface energy budget and its impact on superimposed ice formation (SEBISUP)
During the spring/summer transition, sea ice and snow properties change considerably in response to warming and the eventual reversal of temperature gradients within the snow and ice. Snow melt water percolates down towards the colder snow/ice interface, where it refreezes to form superimposed ice. On sea ice this process occurs probably longer and more intensive than on land, because throughout the summer the ice and underlying seawater is always colder than the snow. In Antarctica superimposed ice may actually form layers of some decimeters in thickness.
The objective of this study is to investigate the main processes and boundary conditions for superimposed ice formation, in recognition of its importance for Antarctic sea ice, and its possible importance for Arctic sea ice in case of environmental changes due to future climate change. This will be performed by means of modeling as well as by combined measurements of the temporal evolution of snow and ice properties and the energy budget.
Activities at the station: 2002:
The field study comprises daily measurements of ice and snow properties and meteorological boundary conditions. Snow and ice temperature, salinity, grain size, density, wetness, and thickness will be determined on the fast ice. At the sampling site, radiative and turbulent fluxes will be recorded continuously to calculate the surface energy balance. The results of the field study will be used to develop and validate a numerical model of snow and ice processes at the onset of summer melt.
The field study comprises of daily simultaneous measurements of ice and snow properties and of the meteorological boundary conditions.
Snow temperature, grain size, density, wetness, snow depth and water equivalent will be determined at selected snow pits on the fast ice on a daily basis.
The radiometric measurements at the sampling site consist of incoming and reflected short-wave solar radiation measured with pyranometers, as well as down- and upward long-wave radiation measured with pyrgeometers.
Air temperature, humidity, wind velocity and wind direction are obtained by an Automatic Weather Station (AWS). Those data will be supplemented by visual observations regarding cloud coverage and further characteristic conditions. The meteorological measurements should be performed continuously to assess the diurnal cycle and any events which could cause snow metamorphism.