Late Wisconsin iceberg calving rates and ice sheet mass balance reconstructed from paleo sea levels, Mount Desert Island, Maine

Lowell, Thomas

'At certain locations, ice sheets terminating in water may provide geological evidence to reconstruct iceberg calving rates and hence ice-sheet mass balance. This concept stems from Brown and others (1992) who reported an empirical relationship for 12 modern tidewater glaciers in Alaska: iceberg calving rate is 27 times the average water depth.' 'The Laurentide ice sheet split into tidewater glaciers in the troughs of Mound Desert Island (MDI) and deposited moraines as sea level transgressed onto the island. Paleo-sea elevation was at least 65 m and probably as high as 90 m; from analysis of valley geometry at 10 locations, this corresponds to iceberg calving rates from 906+-483 to 1354+-477 m/yr.' 'The total ice discharge minus the iceberg calving volume is equal to the change in terminus position times the terminus area. Since the terminus is stationary when moraines are deposited, the calving rate is equal to the discharge at that time. Calculated discharge values for MDI range from 9.2x10(4) to 1.5x10(5) m(3)/yr across a unit width of the terminus. The geometry of the ice mass feeding MDI requires from 0.4 to 0.7 m/yr water equivalent along the entire flowline to balance just iceberg calving. The geometry of this analysis dictates that all of the above estimates are minimum values.' /STUDY LOCATIONS:/ /MOUNT DESERT ISLAND

Late Wisconsin iceberg calving rates and ice sheet mass balance reconstructed from paleo sea levels, Mount Desert Island, Maine

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