Glacier surging Susitna Glacier, Alaska (Ausn Post) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Glacier surging: overview • Definions • Distribuon of “surge-type” glaciers • Observaons • Qualitave characteriscs • Quantave measurements • Surge trigger(s) and mechanism(s) • Underlying controls • Departures from standard model hp://www.genthehotspot.com/kluane-naonal-park- glacier-tour-day-trip-yukon/ Klubbebreen south, Svalbard (M Sund) Lowell Glacier, Kluane Naonal Park Steele Glacier, Yukon Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Glacier surges Internally-driven, episodic flow variaons marked by 10- to 100-fold increases in flow speed [e.g. Meier & Post, 1969; Kamb et al., 1985] Triggered by friconal (thermal, hydrological, mechanical) transitions at the glacier bed [e.g. Kamb, 1987; Clarke et al., 1984; Fowler, 1987; Murray et al., 2003; Sevestre & Benn, 2015] Dusty Glacier, Yukon Territory (G. Clarke) “[A surge] is different from a real advance of a glacier, which is caused by an increase in the volume of ice.” (BBC, 1 Dec 2009) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Glacier surges Rapid flow acceleraon moves mass from reservoir area downstream (surge) Acceleraon due to enhanced basal flow: ub = ub(⌧b,Pw) z x Surge cycle requires the development of an ice reservoir, thus resistance to ice flow during quiescence. Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observed velocity compared to balance velocity Clarke, 1987 balance velocity observed velocity Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Vercal velocity anomalies Example: sustained vs episodic fast flow in Barnes ice cap Modelled surface speed Normal velocity anomaly (difference between observed and expected elevaon changes, 1960-2010) Gilbert et al., in revision Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Geographical distribuon of surge-type glaciers Sevestre & Benn, 2015 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Iceland NASA MODIS image Björnsson et al., 2003 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Svalbard Jiskoot et al., 2000 Svalbard surges: • return interval: 50-500 yr • duraon: 3-10 yr Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Alaska, Yukon, Brish Columbia Post, Journal of Glaciology, 1969 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Dusty Glacier (surge-type), Yukon Territory (G. Clarke) Kaskawulsh Glacier (not a surge-type glacier), Yukon Territory (G. Clarke) Strongly contrasng flow behavior between glaciers Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs St. Elias Mountains (A. Post) Asynchronous behavior not clearly related to climate forcing Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs “Looped” moraines: geomorphic evidence for pulsing flow Yanert Glacier, Alaska Range (A. Post) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs “Looped” moraines Black Rapids Glacier, Alaska (USGS) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs “Looped” moraines Susitna Glacier, Alaska (NASA Earth Observatory) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Extensive crevassing Síðujökull surge, Vatnajökull, February 1994 (H. Björnsson) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Chaoc crevassing Hagafellsjökull surge, Langjökull, 1998 (H. Björnsson) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Surge-front propagaon Síðujökull surge, Vatnajökull, 1994 (H. Björnsson) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Surge-front propagaon Trapridge Glacier, Yukon (Clarke et al., 1984) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Rapid advance Síðujökull surge, Vatnajökull, February 1994 (H. Björnsson) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Evidence of distributed subglacial drainage Síðujökull surge, Vatnajökull, March 1994 (H. Björnsson) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Projecon of bed topography to surface Tungnaarjökull in Vatnajökull, November 1994 (H. Björnsson) High raos of basal moon to deformaon result in the projecon of bed topography at the glacier surface Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Projecon of bed topography to surface Dyngjujökull surge, north Vatnajökull, 1998 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: quantave measurements Reservoir and receiving areas, 2000-1998 Dyngjujökull, north Vatnajökull (Björnsson et al., 2003) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: qualitave characteriscs Mass transfer from reservoir to receiving areas before Jul 1982 aer July 1983 Kamb et al., 1985 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Observaons: measured velocies and lateral shear margins Kamb et al., 1985 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Surge trigger: switch in basal drainage system “Slow” system “Fast” system Kamb et al., 1985 Diagrams courtesy of T. Creyts Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Surge trigger: return interval Cumulave mass balance, Variegated Glacier, 1947-2004 Early surge onset 1995 surge terminated prematurely aer two hoest days ever recorded in nearby Yakutat (Eisen et al., 2005) Harrison et al., Journal of Glaciology, 2008 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Hydrological surge mechanism for temperate glaciers B. High ice discharge reduces glacier thickness, thus basal drag A. High sliding velocity traps water under the glacier by suppressing C. Low velocies allow channel formaon channel formaon, water escapes D. Glacier thickens, increasing gravitaonal driving stress and basal drag Aer Fowler (1987) in van der Veen (1999) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Hydrological surge mechanism for temperate glaciers Inferred evoluon of basal fricon prior to and during the 1982-83 surge of Variegated Glacier Jay-Allemand et al., 2011 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Surge mechanism for polythermal glaciers Murray et al., 2003 Clarke et al., 1984 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Underlying controls: climate? High Arcc Mountain Asia Arcc Canada Sevestre & Benn, 2015 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Underlying controls: geometry, topography? Correlaon between surge tendency and slope can be explained by surge tendency−length correlaon and length−slope correlaon. Clarke, 1991 Sevestre & Benn, 2015 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Underlying controls: geology? Mulvariate analysis of surge-type glaciers in Svalbard Variable is significant at 95% level Jiskoot et al., 2000 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Underlying controls: geology? Surge-type vs non-surge-type glaciers disnguished by sediment size in metasedimentary basins and mineralogy in mixed lithology basins: sediment size sediment mineralogy 0.4 PC1 = 67.5% PC2 = 22.4% 0.2 0 load -0.2 -0.4 -0.6 11.5 10.5 9.5 8.5 7.5 6.5 5.5 4.5 3.5 log (grain size)(mm) 2 Glacier type Glacier type MetaMetasedimentarysedimentary non-s surgeurge (MS-S)(MS-NS) MetaMetasedimentarysedimentary sur genon-surge (MS-S) (MS-NS) MixMixeded non-su surgerge (MX-S) (MX-NS) MixMixeded s urgnon-surgee (MX-S) (MX-NS) Geology Geology Metasedimentary GraMetasedimentarynodiorite MixGranodioriteed volcanic and sedimentary Quaternatry sediment Crompton & Flowers, 2016; Mixed volcanic and sedimentary unpublished data from Crompton, Quaternatry sediment SFU Glaciology Group Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Alaska, Yukon, Brish Columbia Post, Journal of Glaciology, 1969 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Alaska (Western & Central Ranges, Hayes Range, Delta Mountains) Herreid & Truffer, 2015 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Climate, mass balance and the future of surging glaciers “Slow surge” of Trapridge Glacier (Frappé & Clarke, 2007) Vernagerner advancing, 1844 (aer Thomas Ender, see Hoinkes, 1969) Björnsson et al., 2003 Tributary surges in Panmah Glacier, Karakoram Himalaya (Hewi, 2007) Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University Summary Glacier surges: • last months to a few years • have return intervals of years to decades • oen begin in winter • are usually accomplished predominantly by basal moon • require warm-based ice or substrate (N but not S) • require inefficient drainage systems (N but not S) • appear to be of two types (temperate vs polythermal) • are influenced but not driven by climate • appear linked to glacier geometry/topography, climate/ environment, thermal structure, geology • are changing with climate Photo: Tweedsmuir Glacier, 2008 Glacier surging McCarthy Summer School, 2016 Gwenn Flowers, Simon Fraser University .