Crucial to the survival of a glacier is its mass balance, the
difference between accumulation and ablation (melting and
sublimation). Climate change may cause variations in both
temperature and snowfall, causing changes in mass balance.
Changes in mass balance control a glacier's long term behavior.A
glacier with a sustained negative balance is out of equilibrium
and will retreat. A glacier with a sustained positive balance is
out of equilibrium and will advance.
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Glacier Mass Balance Forecasting NORTH CASCADE GLACIER CLIMATE PROJECT Mauri S. Pelto, Director NCGCP Nichols College, Dudley, MA 01571 |
| Glacier Mass Balance Basics | North American Glacier Mass Balance | Glacier Mass Balance Prediction | Glacier Mass Balance Forecasting | Global Glacier Mass Balance | North Cascades Glacier Mass Balance |
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What is mass balance? Annual balance is the most sensitive annual glacier climate indicator. This sensitivity to climate indicates that climatic driving forces may allow forecasting of the mass balance. A mass balance forecast is valuable as it identifies the amount of glacier runoff that will be produced, which in turn will be key to water management decisions. North Cascade glaciers annual balance has averaged -0.54 m/a of water equivalent from 1984-2006, a cumulative loss of over 12.4 m in glacier thickness or 20-40 % of their total volume since 1984 due to negative mass balances. With more than twenty years of glaciers from ten different glaciers we have tested a forecasting tool for glacier mass balance. The forecasting relies on monthly data for October - April to forecast mass balance for the hydrologic year which ends in October. The forecast thus is given at the start of the melt season and provides an assessment of the amount of glacier runoff that will be generated. We are also working on predictions of mass balance based simply on monthly climate data. This years forecast issued May 1 is for negative glacier mass balance. Mass balance prediction. |
Locations of glaciers, SNOTEL sites and weather stations used in this study. |
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Table 4. The columns are respectively: Mean value of winter PDOW (October-April). Winter ENSOW (October-April). Glacier net balance bn-SC from South Cascade Glacier 1960-2005. Glacier annual balance ba-NC for the 10 NCGCP glaciers (1984-2006). The relative phase: positive, >0.2 (p), negative, <-0.2 (n) and equilibrium -0.2 to 0.2 for equilibrium (e), for PDOW, ENSOW indices and glacier net balance and annual balance (bn-ba) respectively. The number of the rule utilized from section 5. Lastly if the rule correctly yields the annual balance in terms of negative, equilibrium or positive it is noted by a yes, if not a no for both bn-ba . The rule is correct in 41 of 46 years for the South Cascade Glacier for which the model was designed. The rule is correct in 20 of 23 years for the North Cascade Glacier Climate Project glaciers.
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