Page 569 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

now
geosystems
Tidewater Glaciers
and Ice Shelves Give
Way to Warming
Warming air and ocean tempera- tures are causing changes to snow and ice features across the globe, and these changes are per- haps most visible along the coasts of the arctic region, greenland, and ant- arctica. With ongoing warming, tidewa- ter glaciers—large masses of glacial ice flowing downhill toward the sea—are in- creasing their flow rate and calving more frequently, breaking off large icebergs into the surrounding ocean. ice shelves— thick, floating platforms of ice that extend over the sea while still attached to conti- nental ice—are thinning and breaking up, forming icebergs hundreds to thousands of square kilometres in size. Let us look at some notable examples of these effects.
Petermann Glacier, Greenland in northwest greenland, calving of the Petermann glacier has released huge chunks of ice into the sea in recent years. in august 2010, an island of ice measuring 251 km2 broke loose,
along the edge of the ice sheet are melting more rapidly than the ice sheet itself.
Ward Hunt Ice Shelf, Canada along the northern coast of Canada’s ellesmere island is the Ward Hunt ice Shelf, largest in the arctic. after remaining stable for at least 4500 years, this ice shelf began to break up in 2003 and broke into separate pieces in 2011.
The breakup of an ice shelf does not directly influence sea level because the ice shelf mass has already displaced its own volume in seawater. However, ice shelves hold back flows of grounded ice that, while not yet displacing ocean water, are moving toward the sea. as the ice shelves disappear, their buttress- ing effect is lost, allowing the glaciers to flow more rapidly. This region of the Canadian archipelago ranks third behind the antarctic and greenland ice Sheets in terms of ice-mass loss on earth, and this melting ice is making a significant contri- bution to global sea-level rise.
Pine Island Glacier, Antarctica To the west of the antarctic Peninsula, the Pine island glacier flows from the West antarctic ice Sheet to the amundsen Sea (noted on Figure 17.7). This glacier is one of antarctica’s largest ice streams, a type of glacier that flows at a faster rate than the surrounding ice mass. The flow rate of the Pine island glacier is accelerating, increasing by 30% since 2000.
The Pine island glacier’s 40-km-wide ice shelf is also calving and thinning at higher rates than previously recorded. This small ice shelf and glacier help buttress downslope movement of the West ant- arctic ice Sheet, which already contributes 0.15 to 0.30 mm·yr−1 to sea-level rise.
The warming trends demonstrated in these examples continued through 2014, promoting the rise of sea level across the globe. in this chapter, we examine snow, ice, and frozen ground, and the rapid changes that are occurring in these envi- ronments with climate change.
geosystems now online gotoChapter17 on the MasteringGeography website (www.masteringgeography.com) for more on melting ice shelves and glaciers, or to the national Snow and ice Data Center at nsidc.org. For the latest ice conditions in Canada, go to www.ec.gc.ca/glaces-ice/ default.asp?lang=En&n=D32C361E-1.
forming the largest iceberg in the arctic in a half century (equivalent to 25% of this glacier’s entire floating ice shelf). Then in July 2012, another large iceberg broke off the tongue of the glacier, farther upstream than the 2010 event (Figure gn 17.1).
With warmer air melting ice from above and higher sea temperatures melting ice from below, the rate of glacial loss in- creases. Scientists are studying how these processes apply to the Petermann glacier. new cracks are opening upstream on the ragged edges of the glacier, demonstrat- ing forward-moving stress. Data show that the greenland ice Sheet as a whole, which covers about 80% of the landmass, is now melting at a rate three times faster than in the 1990s. glaciers such as Petermann
July 16, 2012
Petermann
Glacier 10 km
N
Petermann
July 17, 2012 Glacier 10 km N
▲Figure GN 17.1 Greenland tidewater glacier breakup, 2012. an iceberg breaks off the Petermann glacier. notice at least five tributary glaciers. [Aqua MODiS, naSa.]
533