May 22, 2017
Besselsbreen Retreat Glacier Wide Thinning , Svalbard
Posted by Mauri Pelto
Besselsbreen (B) and Augnebreen (A) comparison in a 1990 and 2016 Landsat image. Red arrows indicate terminus position in 1990, yellow arrow indicates terminus in 2016, purple arrows indicate locations of upglacier thinning from 1990 to 2016 and the yellow line indicates the width of the tongue on the eastern side of Besselsbreen to the medial moraine with Augnebreen
Besselsbreen Glacier flows north to tidewater from the Barents Icecap on Barentsoya Island in Svalbard. The glacier has a low slope with the surface elevation reaching 250 m 10 km from the glacier front. The result is limited velocity and crevassing. The lack of crevasses and flow enables formation of interesting surface stream networks as well. Here we examine Landsat imagery from 1990 to 2016 and Google Earth imagery from 2013 to identify key glacier changes. Dowdeswell and Bamber (1995) indicate the glacier has not surged since its Little Ice Age maximum and that the lowest 4 km of the glacier has a bed that is below sea level. Gruell et al (2017) mapped the albedo of the glacier using MODIS and found it quite low all the way to the crest in the summer of 2003. This suggests limited retained snowpack. The recent ocean and atmospheric warming (Isaksen et al , 2016) driving increased summer melt.
In 1990 Besselsbreen extended to within 1.2 km of Kap Bessels on the east side of the glacier and to the embayment widening on the west. The east side of the terminus had a 2.4 km wide tongue that extends beyond the rest of the terminus. There is no lake or tidewater at the terminus of Augnebreen. The snowline is at 500 m near the top of the glacier. In 2000 the eastern tongue of the glacier is 2.0 km wide, the glacier has retreated a minor amount. By 2016 the terminus on the west side of the inlet has retreated 1.9 km and 2.6 km on the east side of Besselsbreen. The eastern tongue of the glacier is now 1.2 km wide. The snowline in mid-August is at 400 m. Significant thinning has exposed substantial new bedrock areas at the purple arrows which are between 250 m and 350 m in elevation. This is indicative of higher annual snowlines leading to significant surface melt driven thinning. The glacier terminus has crevassing only near the embayment where the eastern tongue extends north from the rest of the terminus. This suggest limited calving, no icebergs are noted in any images used. Warming sea temperatures and reduced sea ice are likely playing a role in enhanced near terminus melt rates. The lack of crevasses and extensive melting has led to substantial stream networks and surface ponds on the lower glacier as seen in Google Earth images below. The low albedo of the relatively dark surface of the glacier even near the top underscores the failure to retain snow/firn through the summer allowing dust to accumulate on the surface. The medial moraine between Augnebreen and Besselsbreen will be a continuing location of separation. Augnebreen is retreating less rapidly, 1.2 km from 1990-2016, but now has a significant tidewater embayment at the glacier front that should enhance retreat.
The retreat here is less than the more calving dominated tidewater glaciers such as Hinlopenbreen, Kronebreen or Svitjodbreen. In the case of Kronebreen that glacier has also been separating from Kongsvegen.
Besselsbreen (B) and Augnebreen (A) comparison in a 2000 Landsat image. Red arrows indicate terminus position in 1990, yellow arrow indicates terminus in 2016 and the yellow line indicates the width of the tongue on the eastern side of Besselsbreen to the medial moraine with Augnebreen
Besselsbreen (B) and Augnebreen (A) comparison from TopoSvalbard map
Besselsbreen (B) and Augnebreen (A) comparison from TopoSvalbard image of 2013, yellow arrows indicate 2016 terminus. Note dark color of ice surface.
Besselsbreen in a Google Earth image indicating melt ponds and supraglacial streams. Yellow dots indicate the ice front.