SEDIMENTARY PROCESSES/Glaciers 665 Figure The East Antarctic Ice Sheet near Casey Station, with two small ice streams (zones of crevassed fast flowing ice) discharging into the sea ß 2005, Photograph, M J Hambrey Figure A small ice cap on the north east side of James Ross Island, northern Antarctic Peninsula ß 2005, Photograph, M J Hambrey Glacier Mass Balance Mass balance is the study of the inputs and outputs to the glacial system, i.e the net gain or loss of snow and ice across a glacier (Figure 5) The inputs to the glacial system are known as accumulation and include all materials that add mass to the glacier, such as snow, refrozen slush, hail, frost, rain, and avalanched snow or ice The outputs from the system are known as ablation and include anything that removes mass from the glacier, such as direct ice melt, iceberg calving, wind erosion, and sublimation Mass balance is largely dependent on the prevailing climate since this determines the rates of accumulation and ablation In general, ablation tends to be dominant in the warm summer months, and accumulation is dominant in the winter months (Figure 5B) The exception to this rule is where iceberg calving occurs throughout the year where an ice-sheet or glacier terminates in water The rate of growth or recession of a glacier is determined by the difference between the accumulation and ablation rates (called the net mass balance and usually measured over a year period) The point