March 25, 2021
Snow White Glacier in Landsat images from 2002, 2016 and 2021. Point A is an alpine lake, Point B is new proglacial lake location, Point C is lower icefall and Point D the Upper Icefall. Blue arrows indicate glacier flow.
The Snow White Glacier is in the Snow Drift Range and Olivine Wilderness in Mt Aspiring National Park, New Zealand. The glacier flows north from 2400 m on the slopes of Mount Maoriri and Maruiwi through an icefall at 2000 m (D) and a second icefall (C) at 1700 m before taking a sharp eastward turn for the terminus reach and then draining into the Arawhata River. The NIWA glacier monitoring program noted that 30 per cent of New Zealand’s ice that was existed in the late 1970s has been lost in the past 40 years as snowlines have been rising. The retreat has been driven by a series of increasingly warm summers (NIWA, 2019). The NIWA 2021 snowline survey indicated near normal average end of summer snowline despite a La Nina (Drew Lorrey in NZHerald, 2021). Here we report on changes in Snow White Glacier using Landsat and Sentinel imagery from 2002-2021.
In a 2002 Landsat image Snow White Glacier had a wide terminus tongue filling a basin at Point B ~1400 m in elevation, 600 m from a small lake at Point A. The glacier is 400 m wide at the lower icefall and 600 m wide at Point B. By 2016 the lower icefall reach is down to 200 m in width, which means less ice is flowing from high on the glacier to the terminus. As a result the terminus lobe width has been reduced to 300 m and an incipient glacial lake is forming near Point B. By 2020 in a Sentinel image and Digital Globe image the lake forming at Point B is evident fringing much of the glacier. Notice the snowline reaches the upper icefall in 2020, and the icefall at Point C is too narrow to be stable. The lake in the Digital Globe image has an area of 0.1 km2. The icefall connection is less than 100 m wide and will soon disconnect the upper glacier from the terminus. In 2021 Landsat imagery indicates the terminus lake is continuing to expand and the icefall reach is even more tenuous. The glacier has retreated 450 m since 2002. The impending detachment will lead to a jump in the retreat to the new active terminus in the lower icefall, with the 1 km long stagnant tongue left behind.
This glaciers retreat parallels that of other glacier in the region such as Gunn Glacier and Donne Glacier, where new alpine lakes have recently formed also. The detachment is quite similar to that of Volta Glacier.
Digital Globe 2020 image of the terminus reach of Snow White Glacier indicating new lake near Point B.
Snow White Glacier in Sentinel and Digital Globe image from 2020. Point A is an alpine lake, Point B is a new proglacial lake, Point C is the lower icefall and Point D the Upper Icefall.
Topographic map of Snow White Glacier from NZTopo Map