Modelling rates of sedimentation from icebergs

Abstract

Abstract Icebergs transport debris from ice masses into the glacimarine environment, but iceberg production, debris content and sedimentation rate will vary with glacier dynamics and the nature of marine waters. A model incorporating glaciological and oceanographic parameters calculates the flux of debris calved in icebergs, iceberg melt rates and sedimentation rates with distance from calving tidewater ice fronts. The flux of basal debris calved through a 1 m width of tidewater margin is ( h d c /100) v c , where h d and c are basal debris-rich ice thickness and sediment content (%), and v c is iceberg calving rate. Iceberg basal melting for any horizontal interval (d x ) away from the calving glacier is dy = ( M b d x )/ v b , where M b is iceberg melt rate and v b is horizontal iceberg velocity. Sediment release for any x increment depends on iceberg debris concentration and previous berg melt history. Model parameters vary with the nature of climatic conditions, on a continuum from cold polar environments (e.g. High Canadian Arctic, Antarctic Peninsula), through sub-polar environments (e.g. Baffin Island, Svalbard) to more temperate environments (e.g. SE Alaska). These parameters include: glacier flow velocity, glacier thermal regime, basal debris-rich ice thickness, and marine water temperature. Model results suggest that iceberg sedimentation rates are lowest for high polar settings, and most rapid in warm maritime and some sub-polar areas. However, icebergs in cold waters transport debris to significantly greater distances from the parent glacier. The model provides calculations of order of magnitude rates of iceberg sedimentation in varying glacimarine settings.