Antarctic Iceberg Melt Rates Derived from Size Distributions and Movement Rates
The melt rates of Antarctic icebergs derived by Morgan and Budd (1978) were based primarily on the distribution of iceberg concentrations, data on iceberg size distribution being limited. Recently, more detailed data have been obtained, especially north of lat. 60°S which allow more precise calculations of the changes in size during drifting. On Australian National Antarctic Research Expedition (ANARE) voyages each summer since 1977, observations of icebergs have included photographs, number per unit area from ship’s radar, widths, heights, and shapes. These data have allowed separate calculations to be made for tabular icebergs which give a clearer indication of the contribution to average size changes of melting, breakage, and rollover. New data from satellite transponders placed on icebergs have provided more definite estimates of the average northward and then eastward drift rates of icebergs near 90°E. Combined with the new data on size more accurate melt rates have been derived. Detailed measurements with expendable bathy-thermographs (XBT) along the shipping routes have provided more definite data on water temperature which allow the melt rates to be studied as a function of temperature. Historical data on iceberg locations have been used to estimate the melt and decay rates of the icebergs at higher temperatures.