North Cascade, Washington alpine winter snow pack depth, summer snow pack depth on glaciers, and ablation rates vary widely due to local topography and consequent microclimates. However, is the pattern from year to year consistent for specific elevation bands, so that knowing the specific accumulation depth or ablation rate at a few sites allows extrapolation to other sites at similar elevations. To identify the degree to which annual snowpack development and ablation can be consistently estimated from a few sites the following data sets are utilized: 1) Annual glacier mass balance measurements from eight North Cascade glaciers (NCGCP); 2) Snowpack ablation on five glaciers (4 by NCGCP and 1 by USGS), and six USDA snotel sites; 3) Snowpack development at six snotel sites (USDA) and on two glaciers (NCGCP). Annual balance is the difference of winter accumulation and summer ablation. Cross correlation of annual mass balance (bn) values between each of the eight glaciers, each with differing geographic characteristics, exceeded 0.85 for every combination. The actual bn values had a significant range, however, the response of each glacier to a given years specific climate conditions were remarkably similar.

Ablation has been measured on five glaciers Columbia Glacier, Lyman Glacier, Ice Worm Glacier and Easton Glacier by NCGCP and on South Cascade Glacier by the USGS during no less than seven ablation seasons on each. Mean daily ablation for specific periods are: Early ablation season May 1-June 10, 2.7-3.3 cm/day. Mid-ablation season June 11-August 3,1 6.3-7.1 cm/day. Late ablation season September 1- 30, 3-2.8 cm/day. The variation from glacier to glacier falls within the above ranges. The correlation in mid-season and late season ablation between each glacier exceeds 0.95 indicating the degree to which their individual response to the specific regional climate of the summer is nearly identical. The early season ablation is widely variable, due to the crucial impact of the freezing level determining rain or snow events, ablation or accumulation conditions. This is also noted at the snotel sites which have a widely varying ablation rate from April 15-May 15, and similar ablation rates thereafter. Significant glacier ablation ends by October 1, but, significant accumulation seldom begins prior to November. At the six Snotel sites from November 1-February 15 snowpack development is rapid reaching 68-80% of the maximum snow pack water equivalent (SWE). At 1200-1500 m snowpack development typically ends by April 15. At the primary glaciated elevations 1500+ snowpack development peaks by May 10. The correlation of daily SWE at the three snotel sites between 1400 m and 1700 m ranges from 0.88-0.99. From 1200-1400m the correlation coefficient is 0.87-0.99. The correlation between the high elevation and low elevation Snotel sites is 0.63-0.96. The mean SWE depth and maximum SWE is widely variable from site to site, however, the annual pattern of development and ablation in response to specific climate conditions is quite similar for each elevation band. The primary conclusion is that local climate in the North Cascades influences mean snowpack depth and ablation rate, but does not result in significantly different responses to specific annual climate conditions within specific elevation bands. Extrapolation from site to site thus can only be accomplished if the sites are at similar elevations and the sites have a baseline history documenting the specific development of snowpack and early season ablation r ates.