Tidewater glaciers of Svalbard: Recent changes and estimates of calving fluxes

The purpose of this study is to describe the current state of tidewater glaciers in Svalbard as an extension of the inventory of Hagen et al. (1993). The ice masses of Svalbard cover an area of ca 36 600 km2 and more than 60% of the glaciated areas are glaciers which terminate in the sea at calving ice−cliffs. Recent data on the geometry of glacier tongues, their flow velocities and front position changes have been extracted from ASTER images acquired from 2000–2006 using automated methods of satellite image analysis. Analyses have shown that 163 Svalbard glaciers are of tidewater type (having contact with the ocean) and the total length of their calving ice−cliffs is 860 km. When compared with the previous inventory, 14 glaciers retreated from the ocean to the land over a 30–40 year period. Eleven formerly land−based glaciers now terminate in the sea. A new method of assessing the dy− namic state of glaciers, based on patterns of frontal crevassing, has been developed. Tide− water glacier termini are divided into four groups on the basis of differences in crevasse pat− terns and flow velocity: (1) very slow or stagnant glaciers, (2) slow−flowing glaciers, (3) fast−flowing glaciers, (4) surging glaciers (in the active phase) and fast ice streams. This classification has enabled us to estimate total calving flux from Svalbard glaciers with an accuracy appreciably higher than that of previous attempts. Mass loss due to calving from the whole archipelago (excluding Kvitøya) is estimated to be 5.0–8.4 km3 yr−1 (water equiv− alent – w.e.), with a mean value 6.75 ± 1.7 km3 yr−1 (w.e.). Thus, ablation due to calving con− tributes as much as 17–25% (with a mean value 21%) to the overall mass loss from Svalbard glaciers. By implication, the contribution of Svalbard iceberg flux to sea−level rise amounts to ca 0.02 mm yr−1. Also calving flux in the Arctic has been considered and the highest an− nual specific mass balance attributable to iceberg calving has been found for Svalbard