Glaciers

(These parameters apply to the Soil Moisture method.)

The optional glacier module can track the accumulation and melt of ice on the land surface.  The depth of ice increases or decrease because of old snow transforming into ice, or existing ice melting.  Snow which has not melted after twelve months transforms into ice.  Ice will melt only if there is no snow covering it, and the temperature is above a threshold.  

Depending on the Climate Data setting in General: Basic Parameters, the values for several of these variables (Initial Ice Depth, Ice Melting Point and Radiation Coefficient) can either be entered once for each catchment and will apply to all the land use branches within that catchment, or they will be entered separately for each branch within each catchment. This second option might be necessary if there is a large variation in the elevation among different land use branches within a catchment. Alternatively, the catchment could be divided into several different catchment nodes according to elevation, so that the climate within each catchment did not vary by land use.

Model Glaciers?

Check the box to model glaciers in catchment -- ice accumulation (old snow becomes ice) and melt.  Only catchments using the Soil Moisture Method can model glaciers.  The "Model Glaciers?" variable tab is located in the "Advanced" category.  

The following variables, which only appear if "Model Glaciers?" is checked, are under the category: Glacier:

Initial Ice Depth

Initial value for ice depth (melt water equivalent) at the beginning of the first month.

Ice Melting Point

Temperature at which ice begins to melt.

Radiation Coefficient

Percentage of net radiation that contributes to melting ice.

Groundwater Infiltration

Percentage of glacier melt that infiltrates directly to groundwater.  If this percentage is greater than zero, the catchment must be linked to a groundwater node.

Scaling Factor b, Scaling Factor c

Volume = c * Areab, based on a published empirical relationship that relates glacier ice volume (V) expressed in km^3 to glacial area (A) in km^2 for individual glaciers (Bahr et al. 1997), b and c are scaling factors related to the width, slope, side drag and mass balance of a glacier. Analysis of 144 glaciers around the world suggests factor values of b = 1.36 and c = 0.048.   Bahr, D. B., M. F. Meier, and S. D. Peckham. 1997. The physical basis of glacier volume-area scaling. J. Geophys. Res. 102 (B9): 2035520362.

See also: Soil Moisture Method Calculation Algorithm

Entered on: Data View, Branch: Catchments, Category: Advanced, Tab: Model Glaciers;  Category: Glaciers, Tabs: Initial Ice Depth, Ice Melting Point, Radiation Coefficient, Groundwater Infiltration, Scaling Factor b, Scaling Factor c.