April 9, 2020

Rainbow Glacier Fieldwork 8-7-2018

Posted by Mauri Pelto

The video is of a single day of field work on Rainbow Glacier on 8-7-2018.  This was our 702nd day of fieldwork during the project that began in 1984.  On this day the field team consisted of Mariama Dryak, Erin McConnell, Jill Pelto and Mauri Pelto. Rainbow Glacier is a valley glacier on the northeast flank of Mount Baker, a stratovolcano and the highest mountain in the North Cascade Range, Washington.  The glacier begins at a saddle at 2200 m sharing a divide with Mazama and Park Glacier.  The glacier descends from the saddle through an icefall at 1950 m into the Rainbow Creek valley terminating at 1400 m.  The consistent accumulation area extends from 1800 m to the saddle region above 1950 m. The glacier tongue features a deeply incised supraglacial stream channel.  From 1984-2018 cumulative mass balance loss has exposed several bedrock knobs along the southern margin of the glacier.

Runoff from the glacier drains into Baker Lake, a reservoir for the Baker Dam hydropower facilities that have a generating capacity of 215 MW. Rainbow Glacier advanced during the 1950-1979 period building a terminal moraine.  At the time of the first field season in 1984 the glacier was still in contact with this moraine.  From 1984-2018 the glacier has retreated 620 m. In 2018 the mass balance was -0.53 m.

Terminus of Rainbow Glacier in 2018


Figure 1 is a map of the Rainbow Glacier indicating the mass balance measurement network.


Mass balance map of Rainbow Glacier in 2017 with mass balance isoline in m of water equivalent (Map by Ben Pelto)