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Store Glacier

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Store Glacier as seen from space by the Taiwanese Space Agency's FORMOSAT-2 sensor on 28 June, 2008. Image horizontal resolution is 4 m.
Store Glacier from approx. 4000 feet on 17 August 2009. Notice the area of open water on the right side of the image. Photo by Jason Box.
Store Glacier Weidick et al. (1995) "Oblique aerial photograph of the front of Store Gletscher taken 15 July 1948, looking southeast". The area of open (calf ice free) water at the south side of the glacier front is persistent in summer as buoyant fresh water rises up from depth along the glacier front. This melt water plume is sediment rich, indicating melt water communication at the glacier bed.

Store Glacier or the Danish Store Gletscher, known also in Greenlandic as Qarassap Sermia, great glacier to the east) is a major west Greenland outlet to the inland ice sheet, producing approximately 14–18 cubic km ice per year, flowing at a speed of 4.2–4.9 km per year (Weidick and Bennicke, 2007). This study ranks the glaciers ice output as second only to Sermeq Kujaleq (a.k.a. Jakobshavn Glacier) east of Ilulissat. The front of Store Gletscher has remained in approximately the same position for the 40 years until the production of Weidick (1995, p. C41). Ice-thickness data remain unavailable for the lower 20 km of Store Glacier. Yet, calving-front freeboard height of up to 70 m imply thickness of ~500m.

Store glacier undergoes mid-summer deceleration that indicates the effects of subglacial meltwater discharge and drainage system evolution. Drainage of supraglacial lakes and water-filled crevasses results in a 40–60% mid-summer speed decrease (Howat et al. 2010).

Ahn and Box (2010) use time lapse photogrammetry to measure glacier front velocities in the range of 9 to 15 m per day in the period June through September 2007. Significant speed increases are associated with major calving events that reduce internal resistance to flow.

The calving front advances and retreats seasonally with an average range of 400 m (Howat et al. 2010). The 2008 annual effective length fluctuation measured by Jung et al. (2010) was 650 m. This fluctuation correlates with the formation and disappearance of an ice mélange, a conglomeration of semi-bonded calf and sea ice.

Major calving events occur at high tide and when the diurnal tidal range is high (Jung et al. 2010). The intervals between each major calving event are almost 30 days, corresponding with tidal fluctuations.

On 28 May, 2008, a sudden mélange clearing was caused by strong and sustained (25 m/s) winds that broke up the seasonal (ice shelf) mélange and pushed it down the fjord. Melt onset had already begun by this date. Therefore, some weakening of the ice berg and sea ice bonds was already progressed.

For 6 glaciers in the Uummannaq District (UD), the average first day of mélange clearing varied by 30 days between 2000 and 2009, with an earliest date of 26 May (2003) and a latest date of 25 June (2001). Store glacier in the south of UD clears on average 17 days earlier than Umiamako glacier in the north of UD.

In the following 10 years beginning with year 2000, the average mélange clearing date is 29 May (Howat et al. 2010). Here are the 10 years of dates: 163 156 146 136 150 134 142 153 152 157.

The advance typically occurs rapidly in April and May, reversing to a similarly brief period of rapid retreat near the time of mélange clearing. Average melt-season speeds remained stable between 2000 and 2009, varying <10%, with the exceptions of 2002 and 2005, when speed decreased by 30–60% in mid-summer. The time series of speed at a point ~30km inland over the same period in Joughin and others (2008) displays little variation in speed, suggesting that the magnitude of speed variability decreased inland.

The timing of the anomalous decelerations in 2002 and 2005 at Store Gletscher coincides with drainage of surficial meltwater lakes visible in satellite imagery {Howat et al. 2010, Fig. 10). Between 1 and 24 July 2002, a period which brackets the peak in speed and initial decline, a 2.2 sq km lake located 17 km above the ice front completely drained. This lake had not drained in the previous year. Between 16 July and 8 August 2008, a period which brackets the period of peak speed, another, 3.5 sq km, lake located 3km further upstream drained completely while the lower lake grew in area by over 50%. This lake remained approximately the same size until 17 August, and then drained completely by 26 August as glacier speed declined to approximately 60% of the peak.

Walter et al. (2012) examine data from: 4 broadband seismometers; 3 time-lapse cameras; a tide gauge; an automatic weather station; and an on-ice continuous GPS station. Sub-daily fluctuations in speed coincide with two modes of oceanic forcing: 1.) the removal of the ice mélange from the terminus-front and 2.) tidal fluctuations contributing to speed increases following ice mélange removal. Tidal fluctuations in ice flow speed were observed 20 km from the terminus and possibly extend further. Seismic records infer bursts of calving activity that cluster near positive speed increases occurring after the mélange breaks up. A synchronous increase in speed at the front and clearing of the mélange, suggests that the mélange directly resists ice flow. A buttressing stress of 30-60 kPa seems to be due to the presence of the ice mélange that is greater than the range of observed tides, though an order of magnitude less than the driving stress.

Works Cited

  • Ahn, Y. and J.E. Box, 2010: Glacier velocities from time lapse photos: technique development and first results from the Extreme Ice Survey (EIS) in Greenland, J. Glaciol., 56(198), 723-734. PDF
  • Howat, I.M., J.E. Box, Y. Ahn, A. Herrington and E.M. McFadden, 2010, Seasonal variablity in the dynamics of marine-terminating outlet glaciers in Greenland, Journal of Glaciology, 56, 198, 601-613.
  • Joughin, I. and 7 others. 2008. Continued evolution of Jakobshavn Isbrae following its rapid speedup. J. Geophys. Res., 113(F4), F04006. (10.1029/2008JF001023.)
  • Jung, J. J. E. Box; J. D. Balog; Y. Ahn; D. T. Decker; P. Hawbecker, Greenland glacier calving rates from Extreme Ice Survey (EIS) time lapse photogrammetry, C23B-0628, American Geophysical Union, San Francisco.
  • Walter, J.I., J.E. Box, S. Tulaczyk, E.E. Brodsky, I.M. Howat, Y. Ahn, and A. Brown, Oceanic mechanical forcing of a marine-terminating Greenland glacier, Annals of Glaciology, revised 6 Feb, 2012.
  • Weidick, A. 1995. Greenland. In Williams, R.S., Jr and J.G. Ferrigno, eds. Satellite image atlas of glaciers of the world. Denver, CO, US Geological Survey, C1–C105. (USGS Professional Paper 1386-C.)
  • Weidick, A. and O. Bennike, 2007. Quaternary glaciation history and glaciology of Jakobshavn Isbræ and the Disko Bugt region, West Greenland: a review, Geological Survey of Denmark and Greenland, Bulletin 14, 80 pp, 2007. using data from Bauer, A., Baussart, M., Carbonnell, M., Kasser, P. Perroud, P. & Renaud, A. 1968a: Missions aériennes de reconnaissance au Groenland 1957–1958. Observations aériennes et terrestres, exploitation des photographies aériennes, détermination des vitesses des glaciers vêlant dans Disko Bugt et Umanak Fjord. Meddelelser om Grønland 173(3), 116 pp. and Carbonnell, M. & Bauer, A. 1968: Exploitation des couvertures photographiques aériennes répétées du front des glaciers vélant dans Disko Bugt et Umanak Fjord, juin–juillet 1964. Meddelelser om Grønland 173(5), 78 pp.

Field Campaigns

Store Glacier 2008 field work

Store Glacier 2009 field work

Store Glacier 2010 field work

Store Glacier 2012 field work including Operation Iceberg


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