Utility of late summer transient snowline migration rate on Taku Glacier, Alaska

Abstract

Abstract. On Taku Glacier, Alaska a combination of field observations of snow water equivalent (SWE) from snowpits and probing in the vicinity of the transient snowline (TSL) are used to quantify the mass balance gradient. The balance gradient derived from the TSL and SWE measured in snowpits at 1000 m from 1998-2010 ranges from 2.6-3.8 mm m −1 . Probing transects from 950 m-1100 m directly measure SWE and yield a slightly higher balance gradient of 3.3-3.8 mm m −1 . The TSL on Taku Glacier is identified in MODIS and Landsat 4 and 7 Thematic Mapper images for 31 dates during the 2004-2010 period to assess the consistency of its rate of rise and reliability in assessing ablation for mass balance assessment. For example, in 2010, the TSL was 750 m on 28 July, 800 m on 5 August, 875 m on 14 August, 925 m on 30 August, and 975 m on 20 September. The mean observed probing balance gradient was 3.3 mm m −1 , combined with the TSL rise of 3.7 m day −1 yields an ablation rate of 12.2 mm day −1 from mid-July to mid-Sept, 2010. The TSL rise in the region from 750-1100 m on Taku Glacier during eleven periods each covering more than 14 days during the ablation season indicates a mean TSL rise of 3.7 m day −1 , the rate of rise is relatively consistent ranging from 3.1 to 4.4 m day −1 . This rate is useful for ascertaining the final ELA if images or observations are not available near the end of the ablation season. The mean ablation from 750-1100 m during the July-September period determined from the TSL rise and the observed balance gradient is 11-13 mm day −1 on Taku Glacier during the 2004-2010 period. The potential for providing an estimate of b n from TSL observations late in the melt season from satellite images combined with the frequent availability of such images provides a means for efficient mass balance assessment in many years and on many glaciers.

Juneau Icefield Mass Balance Program 1946–2011

“…Taku Glacier attracts special attention because of its continuing, century-long advance (Pelto and Miller, 1990;Post and Motyka, 1995;Motyka and Echelmeyer, 2003), while all other outlet glaciers of the Juneau Icefield are retreating. Taku Glacier is also the thickest glacier yet measured in Alaska, 1477 m at an elevation of 800 m (Nolan et al, 1995).…”

An approach to derive regional snow lines and glacier mass change from MODIS imagery, western North America

“…The MOD10 snow cover product (Hall et al, 2002), based on normalised difference snow index (NDSI) thresholds, has been used to estimate snow line elevations on large glaciers (Pelto, 2011), validate hydrological models (Parajka and Blöschl, 2008) and to map snow cover in large watersheds (Déry and Brown, 2007). Unfortunately, the 500 m resolution of the MOD10 product and its poor discrimination between snow and ice facies (Hall and Riggs, 2007) make it less suitable for use on mountain glaciers.…”

Multi-decadal mass balance series of three Kyrgyz glaciers inferred from transient snowline observations

“…In this study we used three independent methods to reconstruct robust mass balance series at high temporal resolution for 20 Abramov, Golubin and No. 354 located in the Pamir-Alay and Tien Shan mountains for the past two decades -a period for which only little is known about glacier behaviour.…”

“…Some pioneer studies (e.g., Østrem, 1973, 1975Young, 1981;Dyurgerov et al, 1994) have identified the value of transient snowline observations in connection with subseasonal mass balances. Recent studies (e.g., Hock et al, 2007;Pelto, 2010Pelto, , 2011Huss et al, 2013;Hulth et al, 2013) have further developed this concept to improve mass balance monitoring and modelling strategies, including information extracted from continuous snowline observations. However, most approaches still rely on long-term glaciological information and are thus not applicable to inaccessible 5 glaciers located in remote and unmeasured regions.…”

“…In this arid continental region, the intensely populated and irrigated downstream areas strongly depend on a supply of water from the cryosphere such as glaciers and snow (Kaser et al, 2010;Schaner et al, 2012;Duethmann et al, 2014;Chen et al, 2016;Huss et al, 2017). The uncertainty of water availability in the context of a changing climate creates a major potential for political tension and builds a complex set of future 20 threats, affecting different sectors such as water management, energy production and irrigation (Varis, 2014;Munia et al, The Cryosphere Discuss., https://doi.org/10. 5194/tc-2017-256 Manuscript under review for journal The Cryosphere Discussion started: 27 November 2017 c Author(s) 2017.…”