August 21, 2022

Speel Glacier Retreats out of Alaska

Posted by Mauri Pelto

Speel Glacier in 1984 and 2022 Landsat images illustrating lake expansion and detachment of tributaries A-C. Red arrow is 1984 terminus location and yellow arrow is 2022 terminus location.

In 1984 I observed Speel Glacier while flying into Juneau, AK to work with the Juneau Icefield Research Program. Speel Glacier is south of the Taku Inlet and the Juneau Icefield draining west from a shared accumulation area with Wright Glacier. Unlike the map on my lap, there was now a big lake at the terminus of the glacier. This post examines the retreat of this glacier across the international boundary, out of Alaska, and the expansion of the unnamed lake at its terminus using Landsat images.

Speel Glacier terminus on 8-18-2022 with the Alaska/British Columbia boundary in blue.

In 1948 Speel Glacier ended at the head of a braided outwash plain, generated by the Speel River. Upglacier in 1948 there was a small side valley lake impounded by the glacier, Speel Lake. The lower part of the glacier was heavily debris covered and stagnant in 1948.  I  In the 1984 Landsat image the glacier had retreated 3 kilometers from the 1948 position and was fed by four separate tributaries flowing into the glacier A-D.  n 1984 the original Speel Lake had drained and a new lake had formed filling the valley that the glacier had filled in 1948. The proglacial lake was 2.2 km long. By 2003 the glacier had retreated an additional 1.8 km from 1984 to where the lake bends east, and the main tributary from the north separated from the glacier prior to 1984. By 2013 tributaries A and B had been completely separated.  In 2022 the glacier has retreated  6.35 km since 1948, 3.3 km since 1984 and the connection with the three of the four tribuaries had been lost A-C.  The tributary detachments have led to continued retreat, have reduced input to the main glacier, which by the summer of 2022 resulted in the glacier retreating across the international boundary from Alaska into British Columbia. The new lake is now over 7 km long, and should be called Speel Lake again. The retreat of this glacier fits the pattern of other glaciers in the region Field, Gilkey, and Tulsequah Glacier  (Pelto (2017). The  detachments are frequent and significanly impact ice dynamics on the Juneau Icefield (Davies et al 2022). There we found 176 such detachments/disconnections in the outlet and valley glaciers of the Juneau Icefield Davies et al (2022).

Speel Glacier in 1948 USGS map.


Speel Glacier in 2003 and 2013 Landsat images illustrating lake expansion and detachment of tributaries A-C. Red arrow is 1984 terminus location and green arrows are detachment of tributaries.