June 10, 2011

Tyndall Glacier, Chile Retreat Continues

Posted by Mauri Pelto

Tyndall Glacier is a large outlet glacier of the Southern Patagonia Icefield (SPI). This glacier has an area of over 300 square kilometers. The main glacier terminus ends in Lago Geikie, which began to form around 1940, and the east terminus previously terminated in Lago Tyndall. Raymond et al (2005) report that the glacier had receded 5 km from 1945 to 2001. The retreat is illustrated in a figure from Rivera & Casassa (2004). This web page on the Tyndall Glacier is one of many provided by Andrés Rivera at the Laboratorio de Glaciología at Universidad de Chile. Assessing the ice surface elevation changes on three profiles 8-15 km above the terminus, the amount of thinning was determined by Raymond et al (2005). From 1945-2002 the average thinning rate of the glacier at meters was 2.3 meters per year. The rate has accelerated averaging over 3.3 meters per year since 1985. This has driven the retreat. Lago Geikie is a deep lake with maximum depths reaching 400 meters and was 300 meters at the calving front in 2001 Raymond et al (2005) . This allows for considerable calving of the thick Tyndall Glacier, which is grounded on the bottom of the lake at its terminus. The glacier velocity near the calving front is 700 meters per year. A comparison of the terminus position from the aforementioned papers, Google Earth from 2003 (top Image) and a Geoeye image from 2010 (bottom image) indicates the changes of Tyndall Glacier are ongoing. Lago Tyndall (LT) for example is continuing to contract as the terminus (TE) that feeds it has thinned and pulled back from the valley that feeds it. Increasingly this is becoming a watershed that will not be fed by Tyndall Glacier. Lago Geikie (LG) continues to expand now 7 km long. The retreat in the last 7 seven years has been 600-900 m on the main calving front. This has exposed a new peninsula (P). The glacier terminus is much narrower than in 1975 in an aerial image from Raymond et al (2005). The snowline on the glacier is at 900 meters and there is considerable glacier area above 1200 meters, indicating this glacier can survive additional warming, note the above image. As Raymond et al (2005) emphasized the glacier bottom remains below the Lago Geikie lake level for 14 km. Over much of this distance calving would play a role, helping continue the recent retreat. This retreat due to calving into a glacier lake resulting from ongoing glacier thinning resulting from increased surface ablation is widespread from Bear Glacier, Gilkey Glacier and Yakutat Glacier in Alaska, to Tasman Glacier in NZ to Nef Glacier and Colonia Glacier in