HR: 1340h
AN: C23A-1150 INVITED     [Abstracts]
TI: Uncertainty in Glacier Mass Balance Measurements
AU: * Fountain, A G
EM: andrew@pdx.edu
AF: Departments of Geology and Geography, Portland State University, 1721 SW Broadway, Portland, OR 97212 United States
AB: Direct, field-based methods of assessing the mass balance of alpine glaciers are based on a set of straightforward measurements of density and surface height change. Measurement uncertainties are generally small relative to the magnitude of the measurement. However, the uncertainties become substantial because the measurements offset each other due to zones of snow accumulation and zones of ice and snow loss. This issue becomes increasingly important as the glacier approaches equilibrium and the mass balance value approaches zero. Under near-equilibrium conditions, the uncertainty may overwhelm the magnitude of the mass balance and it is impossible to determine whether the glacier is gaining or losing mass. All too often methods are used to calculate glacier mass balance that ignores uncertainty in the measurements, which yields a very poor estimate of uncertainty in the final value. Another problem is systematic errors in the measurements. Combining different methodologies, which rely on different set of assumptions, provides an important check on both approaches. Remote sensing plays a vital role in this regard. Understanding uncertainties are important for not only defining the response of glaciers to climate change but also for quantifying the effect of glaciers on local stream flow and on global sea level rise. This paper will examine the source of uncertainties in the measurements and calculations of glacier mass balance, and provide some recommendations for future improvements.
DE: 0700 CRYOSPHERE (4540)
DE: 0720 Glaciers
DE: 0738 Ice (1863)
DE: 0762 Mass balance (1218, 1223)
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005