On The Nature of Svalbard Icebergs

Abstract

Abstract The nature of icebergs calved from Svalbard’s 1030 km of tide-water ice cliffs is related to glacier dynamics and morphology. Both iceberg dimensions and rates of relative iceberg production are affected. Valley tide-water glaciers entering fjords typically calve irregular icebergs of <50 m in length. Ice caps and large outlet glaciers, which predominate in eastern Svalbard, yield small, irregular icebergs and large (>500 m length) tabular icebergs which can travel considerable distances before melting. Surge-type ice masses calve very large numbers of small icebergs during short periods of rapid advance, but few icebergs during longer periods of stagnation and retreat between surges. The nature of iceberg interactions with sea ice also influences the timing and pattern of iceberg production. Winter shore-fast ice traps icebergs close to tide-water ice cliffs. They are released as a pulse on spring-time fast-ice break-up. Pack ice damps waves, and therefore increases iceberg stability and reduces the frequency of overturn. Small icebergs often undergo complete melting and sediment release within fjords. Larger icebergs can be trapped close to glacier termini by shallow bedrock or morainic sills, but some larger, tabular icebergs do escape into the Barents Sea. Implications for iceberg rafting of sediments include the production of large numbers of relatively debris-rich icebergs during surges and the absence of floating ice masses. The latter restricts the loss of debris-rich basal ice by undermelt prior to calving.