Laboratory Manual for Introductory Geology 4e

FIGURE 18.8 Movement of water from the cryosphere to the hydrosphere.
2002 2011
(a) Dramatic recent retreat of the Bear Glacier, Alaska, from 2002 to 2011.
Russia
ATLANTIC
OCEAN
Laptev Sea
Median Extent
Greenland
Bering Sea
Alaska
(U.S.A.)
Canada
(b) Extent of Arctic sea ice, September 11, 2014. The yellow line marks the median extent of sea ice from 1981 to 2010.
As shown in the figure, its current extent is much less.
18.2.4 Changes in the Cryosphere and Hydrosphere
The cryosphere (the Earth’s glaciers and floating sea ice) and hydrosphere (its liquid
water) are intimately related through the hydrologic cycle. When glaciers and
sea ice melt, their water is added to the hydrosphere, and sea level rises; during
ice ages, water evaporated from the hydrosphere becomes part of the cryosphere,
and sea level drops. Today, glaciers throughout the world are retreating rapidly
(FIG. 18.8a) and Arctic sea ice is shrinking to all-time lows (FIG. 18.8b). If melting
continues at the current rate, the Northwest Passage from Europe to Asia sought
by Columbus and other early European explorers will be usable by cargo ships in
10 years. And sea level will rise, affecting hundreds of millions of people.
484 CHAPTER 18 LOOKING TO THE FUTURE