Ice front fluctuation, iceberg calving flux and mass balance of Victoria Land glaciers

The coast of Victoria Land extends from Williamson Head (69°11'S, 158°E) to McMurdo Sound (77°S, 163°E). A comparison of various documents and images spanning several decades has allowed the ice front fluctuation and the iceberg calving flux during this century to be estimated. During the periods from 1956-65 to 1972-73 the floating glaciers underwent a reduction of 978 km2with an iceberg calving flux of about 134 km2yr-1. After this, during the periods from 1972-73 to 1989-91, the floating glaciers underwent an advance of 272 km2with an iceberg calving flux of about 53 km2yr-1. Glacier tongues with bottom accretion calve less often than those with bottom melting. Most floating glaciers have shown cyclic behaviour without a strong trend. Exceptions to this general style are Hells Gate ice shelf, McMurdo Ice Shelf and floating glaciers of Cape Adare which have undergone a significant retreat since the beginning of the 20th century. The different behaviour of these floating glaciers has been hypothesized as being due to: increased energy available for meltwater production of marine ice that progressively warmed these thin ice shelves and then increased iceberg calving (Hells Gate and McMurdo), or to increased melting at the ice-ocean interface related to a major intrusion of Circumpolar Deep Water from the nearby continental slope (Cape Adare). An estimate of the mass balance of East Antarctica from which these glaciers are fed shows a positive value, that is significant despite all the uncertainties of balance measurements.