Page 597 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

witnessed such events and are studying the effects on glacial movement.
Ice Shelves Another recent change in the Canadian Arctic, Greenland, and Antarctica is the breakup of ice shelves, as discussed in Geosystems Now. Ice shelves surround the margins of Antarctica and constitute about 11% of its surface area (see Figure 17.7 for some of the major ice shelves). Although ice shelves constantly break up to produce icebergs, more large sections have broken free in the past two decades than expected. For example, in March 2000, an iceberg tagged B-15, mea- suring approximately 11000 km2 (about 300 long km by 40 km wide), nearly twice the area of Prince Edward Is- land, broke off the Ross Ice Shelf in Antarctica. In 2013, the Wilkins Ice Shelf underwent further disintegration after major breakup events in 2008 and 2009. Scientists think that the recent breakups left the remaining ice more vulnerable, especially in places where the shelf remnants are in direct contact with open water and the force of ocean waves.
Since 1993, seven ice shelves have disintegrated in Antarctica. More than 8000 km2 of ice shelf are gone, re- quiring significant revision of maps, freeing up islands to circumnavigation, and creating thousands of icebergs. The Larsen Ice Shelf, along the east coast of the Antarc- tic Peninsula, was retreating slowly for years. Larsen A suddenly disintegrated in 1995. Then, in only 35 days in early 2002, Larsen B collapsed into icebergs (Figure 17.31). Larsen B was at least 11000 years old.
Larsen C, the next segment to the south, is losing mass from both the ocean and the atmosphere sides.
Since the water temperature is warmer by 0.65 C° than the melting point for ice at a depth of 300 m, this ice loss is likely a result of warmer water, as well as of the air temperature increase in the peninsula region during the last 50 years. In response to the increasing warmth, the Antarctic Peninsula is also experiencing previously unseen vegetation growth, reduced sea ice, and disrup- tion of penguin feeding, nesting, and fledging activities. (Among many changes, ticks are a new problem for these animals.)
Chapter 17 glacial and Periglacial Landscapes 561
CRITICALthinking 17.3
The IPy Accomplishment Continues
The international Polar year (iPy) ran from March 2007 to March 2009, covering two polar summer seasons—it was the fourth iPy conducted since 1882. This global interdisci- plinary research, exploration, and discovery effort involved 50000 scientists in hundreds of collaborative projects. about 65% of the research was in the arctic region and 35% in the antarctic region. a systems approach was em- ployed for finding linkages among ecosystems and human activity. The research effort also made use of the traditional knowledge of indigenous peoples across the circumarctic region—the actual experiences of the First nations people, who are encountering climate change firsthand.
Use your critical-thinking skills in a brief exploration of this iPy. Begin at www.ipy.org. you may choose to “Focus On” the atmosphere, ice, people, or other topics in the list at upper left of the home page. •
0 10 20 KILOMETRES
January 31, 2002
March 7, 2002
▲Figure 17.31 Disintegrating ice shelves along the Antarctic coast. Disintegration and retreat of the Larsen B ice shelf between January 31 and March 7, 2002. note the meltponds in the January image. [Terra images, naSa.]