June 4, 2015
Big Bend Glacier, British Columbia Transitions to Alpine lake
Posted by Mauri Pelto
“Big Bend” Glacier is an unnamed glacier west of Big Bend Peak north of Harrison Lake in Southwest British Columbia. In 1985 the glacier was 2.6 km long filling a low valley with a surface elevation of 1600-1800 m elevation, the topographic map indicates this basic size. Here we utilize Landsat imagery to identify the changes in the glacier from 1985-2014 due to climate change. In essence the glaciated basin is transitioning to an alpine lake basin, quickly.
Topographic map of the Big Bend Glacier area.
In 1985 the glacier extends to the big bend in the valley marking its eastern end, red arrow. the yellow arrow indicates an area near 1800 m where the glacier extends across the valley. In 1992 there has been little retreat but evident thinning is leading to lake formation at the terminus and narrowing of the glacier at the red arrow. In 2002 thinning is leading to expansion of a proglacial lake both west and south of the red arrow. The terminus retreat has still been limited, thinning is evident at the yellow arrow.
In 2013 a new alpine lake that is approximately 1 km long has formed, as the terminus area of the glacier has collapsed. In 2014 an area of bedrock and a small lake has developed at the yellow arrow. There is no retained snowpack below the yellow arrow in 2013, and no retained snowpack in at all in 2014. This will likely be the case in 2015 as well. This glacier has a lower top elevation than most in the region and will be more impacted by the warm winter conditions and high snowline of 2015. The retreat from 1985 to 2014 has been 1.1 km. This is 40% of the entire glacier length gone in 30 years. The lake itself has a deep blue color suggesting limited glacier sediment input, further indicating a lack of motion of the glacier currently or in the near past.
The glacier retreat has been more extensive than Stave Glacier or Snowcap Glacier to its east. Koch et al,(2009) observed a widespread retreat and glacier area loss in Garibaldi Provincial Park just to the west, with 20% area loss from 1988-2005. Place Glacier is a short distance north of Big Bend Glacier has its mass balance has lost an average of 25 m of water equivalent (28 m ice) thickness since 1984, see bottom chart. This has been higher but similar in trend to other glaciers in the region. Big Bend will disappear soon just as we obsserved already happened at Milk Lake Glacier, North Cascades, Washington.
North American cumulative glacier mass balance graph