Description of task
This activity focuses on obtaining improved data on spectral albedo and its role in summer melt, using satellite optical sensors with in situ data from spectroradiometers.
The ice-albedo feedback mechanism is a fundamental climate process affecting both the energy and mass balance of Arctic sea ice on a large scale. It is a key process during snow and ice melt in Arctic summer. Snow and sea ice physical properties affect strongly the energy fluxes at the atmosphere-snow-ice-ocean interfaces.
The variability of the spectral surface albedo from in situ observations (high-resolution spectroradiometers) during icebreaker expeditions (Polarstern, Oden) and on manned and selected unmanned drifting stations (ITPs), together with satellite remote sensing data (optical sensors on ENVISAT MERIS, AVHRR and MODIS) in combination with radar (RADARSAT, ENVISAT ASAR, see “ice types and properties” section) will be analyzed with respect to changing snow and ice characteristics.
The in situ spectrometer data will have a high spatial resolution, and the spectral resolution will allow us to identify and categorize albedo changes according to snow thickness changes, snow texture changes (metamorphism), and impurities.
The dataset will be supported by albedo information from additional investigations in connection with atmosphere studies (core theme 2). Results will be related to classified ice types from scatterometer data and passive microwave data (IFREMER, see “ice types and properties section”), and can be used with respect to atmospheric circulation (core theme 2). In-situ measured optical (transmissivity) and physical properties (salinity, temperature, texture, porosity, impurities) will elucidate the penetration of short-wave radiation into the snow and ice, ice growth and melting, and ice-ocean heat and salt fluxes. It is anticipated that it will be possible to distinguish between solar radiation related melting and ocean heat flux related changes to the mass balance, by consideration of hydrographic data (core theme 3, UPMC).
The data will be used to improve and validate modelled thermodynamic evolution of ice (1-D multi-level thermodynamic ice model by B. Cheng, FIMR). This model is used for examination of the physical parameterisations of the ice thermodynamic processes. The in-situ and remote sensing observations are used for the validation of the modelled penetration and absorption of solar radiation within snow and ice, sub-surface melting and snow-to-ice transformation (further classified into snow-ice formation due to refreezing of flooded ocean and superimposed ice formation due to the refreezing of melted snow) and effect of numerical resolution on the model simulations. First the model is validated with the SHEBA and CHINARE03 data and in the second phase the DAMOCLES date will be used. Uncertainties of the modelled evolution of sea-ice thickness are identified and guidelines for parameterization schemes for ice thermodynamics in large scale models will be given.
