Sea Ice Group at the Geophysical Institute logo1
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Sea Ice Microstructure and Properties

Studies of Microstructural Features and Brine Drainage Networks in First-Year Sea Ice
The objective of this 3-year program is to address gaps in knowledge of the development and evolution of some important macro- and microstructural features of first year sea ice by repeated measurements through the annual cycle from freezing to melting. Topics of study include (1) the geometrical characteristics and spatial distribution of brine drainage networks and their relationship to the crystal structure of the ice, (2) the 3-dimensional characterization of brine and gas inclusions, (3) variations in permeability through the year and the resulting impact on heat and mass transfer through the ice, and (4) details of the relationship between c-axis fabrics and under-ice currents. Knowledge of these is important for studies of the optical and mechanical properties of sea ice, biological activity in sea ice, remote sensing applications, some aspects of climate modeling, and the entrainment and transport of contaminants.
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Tracer Studies of Meltwater Transport and Ablation of Arctic Sea Ice
The generation and redistribution of snow and ice meltwater in summer Arctic pack ice has a significant impact on (1) the surface albedo (in particular through pooling of meltwater at the surface), (2) the vertical and lateral heat and salt transfer in the ice and (3) ice-ocean interaction (in particular through meltwater pooling and freezing under the ice). Meltwater transport and its role in ice ablation were studied from June to August 1998, at the field site of the Surface Heat Budget of the Arctic Ocean (SHEBA (THE WEB DOES NOT EXIST) Program in the North American Arctic. A major aim of the present study was to utilize tracer techniques to determine pathways and rates of meltwater transport and assess the role of "hydraulic" processes in sea-ice ablation.
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Thermal Conductivity of Sea Ice
The thermal conductivity of sea ice is an important parameter in predicting (1) the through-ice conductive heat flux from the ocean to the atmosphere, and (2) the thermodynamic response of the ice to changes in the heat balance. Until recently, the thermal conductivity had not been accurately measured, and most sea ice models used a parameterization that predated the theoretical and the few experimental results. In situ measurements are desirable because of the possibility of a depth-dependence through textural and microstructural variations, and possible enhancement of the heat flow due to convective processes, particularly near the ice/ocean boundary. In collaboration with Victoria University of Wellington ( New Zealand) we have made the most accurate measurements to date, in MY and FY landfast ice, in McMurdo Sound, Antarctica and near Barrow, Alaska. Results show a conductivity that is consistent with composite material predictions but 10-15% higher than that typically used in sea ice models. Our present focus is now on establishing how sensitive sea ice models are to such a difference, and assessing the ease of implementing a new parameterization, which we are likely to propose.