MODIS Studies of Greenland

Sermeq Avannarleq, the next glacier north of the enormous Jakobshavn Isbrae lost more than 2 sq. mi of its ice front by the end of summer 2008. This loss is on top of more than 2 sq. mi lost by end of summer 2007. These recent breakups added to smaller losses in earlier years have generated a retreat pattern illustrated in the lower panel of the figure below.

Sermeq Avannarleq had been dubbed “dead glacier” by local dog sledders that take tourists to the bay in front of this glacier. The name is now illogical. Beginning in 2003, Dead Glacier came alive, shedding floating ice into the forebay and continuing its retreat during 2007 and 2008 summers.

Factoid: Greenlandic glacier names describe the relative location of the feature. Sermeq Avannarleq translated literally means “northern glacier”, north, that is, of Sermeq Kujaleq (southern glacier), that is, Jakobshavn Isbrae.

A 29 sq. km. (11 sq. mi.) area of the Petermann Glacier in northern Greenland (80˚N, 60˚W) broke away between July 10th and by July 24th.

Petermann has a floating section 16 km (10 mi) wide and 80 km (50 mi) long, that is, 1295 sq. km (500 sq mi); the longest floating glacier in the Northern Hemisphere.

Here is an animation of the breakup.

This 2008 breakup is actually not the largest observed. Between 2001 and 2000, 86.8 sq. km (33.5 sq. mi.) broke away from the Petermann front. However, more breakup is immenent in the next year, for, a large crack has widened while moving toward the calving front.

ASTER image courtesy of Ian Howat showing Petermann Glacier crack

Here is an annual (2001-2007) animation Ian Howat made of the crack flowing toward the glacier front while widening.

If the Petermann glacier breaks up back to the upstream rift, the loss would be as much as and additional 160 sq. km (60 sq. mi); a loss of one third of the massive Petermann ice tongue.

The Petermann glacier thins from 600 m thickness at the grounding line to 70 m at the terminus, see [1]. The crack is advancing to a point where a massive breakup seems imminent, in which case, the area of break-up would be 56-60 sq. miles (147-160 sq. km).

Animations:

• Petermann front breakup: small (480×480), large (720×720)
• End of summer 2000 - 2008: small (720×405), large (960×540)
• Annual (2001-2007) animation Ian Howat made of the crack flowing toward the glacier front while widening.

Figures:

• Initial Breakup 1: small (638×826), large (1276×1650)
• Initial Breakup 2: small (975×413), large (1950×825)
• Glacier Front Position 2007-25 July 2008: small (720×540), large (1420×1080)

Addendum (25 Dec, 2008)

Petermann Glacier thins from 600-700 m at the grounding line primarilly due to basal melting [1] calves 0.6 km³ (Higgins, 1990). “The lower 80 km (in length) and 1300 km² (in area) of the glacier is afloat. This makes it (by area) the largest floating glacier in the Northern Hemisphere. “…”The calving front protrudes a mere 5-10 m above sea level, reflecting the fact that the ice at the front is only 60-70 m thick.” M. Pelto, Real Climate.

Work Cited

1. Rignot, E., and K. Steffen (2008), Channelized bottom melting and stability of floating ice shelves, Geophys. Res. Lett., 35, L02503, doi:10.1029/2007GL031765

2. Higgins, A. 1990. Northern Greenland glacier velocities and calf ice production. Polar Forschung, 60, 1-23.

Contact:

• Earle Holland (media relations), +1 614 292 8384; Holland.8@osu.edu

MODIS image of Jakobshavn Glacier with lines indicating continued retreat.

The Jakobshavn Glacier front retreated 14 sq. km (5 sq. mi.) between 6-15 August 2008.

Jakobshavn Glacier is the world’s fastest continuously flowing glacier and the main outlet from the vast 1.69 million sq. km Greenland ice sheet. Jakobshavn drains 6.5% of the ice sheet, producing 35–50 cubic km of icebergs per year [1].

The 2008 retreat is to a position further inland than any time over the past 150 years of direct observation and likely is further back than during any time since the Holocene Thermal Maximum 4-8 thousand years before present, because the interim period ends with the Little Ice Age c. 1250 AD - 1850 AD glacier advance.

Of distinction from a retreat trend mainly at the faster southern branch of Jakobshavn Glacier since 2001, is the northern branch has retreated in the past weeks. Repeat altimeter measurements show the northern branch thinning in recent years at an accelerated rate (Ian Howat, personal communication).

Image with end of summer positions indicated. We measure interannual changes using end of summer images because glaciers reach a seasonal minimum at the end of summer.

Between 2001 and 2005, a collapse of the Jakobshavn Glacier floating tongue removed 94 sq. km (36 sq. mi.).

Additional Figures:

• End of summer 2000-2008: small (720×540), large (1420×1080)
• End of summer 2007-2008: small (720×540), large (1420×1080)

Animations:

• End of summer 2000-17 July 2008: (720×405) (960×540)
• 2008 movement: (480×480), (720×720)

References:

Weidick, Anker and Ole Bennick. Quarternary glaciation history and glaciology of Jakobshavn Isbrae and the Disko Bugt region, West Greenland: a review. Boreas 14 (2007).

Page Constructed by Jason Box, Russ Benson, and David Decker, Byrd Polar Research Center.

Contact:

• Earle Holland (media relations), +1 614 292 8384; Holland.8@osu.edu