ARE SEA LEVELS INCREASING?

1. Are ocean temperatures increasing?

2. Is ice melting throughout the world (in Antarctica, the Arctic, glaciers, and permafrost)?

3. Are sea levels rising?

3. What sources might you use to find the best data to answer these questions? What measurements could be used to obtain the answers?

 OCEAN

There are enormous amounts of water which are trapped in the polar ice caps and in the glaciers of the world. Throughout the majority of the history of the earth, the global temperature was higher than it is today, there were no polar ice caps, and sea level was higher than it is today. For example, in the mid-Cretaceous Period, much of the East Coast was underwater and an inland sea covered much of the interior of the North America. If all the earth's ice were to melt, sea level would increase 150 feet and 15% of the U.S. would be underwater including the entire states of Massachusetts, Connecticut, Rhode Island, New Jersey, Delaware, Florida, and Louisiana and the cities of New York, Philadelphia, Miami, Seattle, and San Francisco (Blatt, 2005). Not only can sea levels rise significantly above modern levels, that would actually be normal considering the condition of the earth in the past 600 million years.

--after Lambeck, 2001

1) OCEAN TEMPREATURE IS RISING


World ocean temperatures are rising and sea level is currently rising at a rate of 1 inch/decade.

--after Gore, 2006

2) GLACIERS AND PERMAFROST ARE MELTING

Glacial ice is melting. A large amount of water is trapped in glaciers on mountains and in permafrost areas close to the poles. Much of this ice is melting as well. In 1992, it was reported that all mid- and low-latitude glaciers were retreating and the ice record within these glaciers indicated that this is the warmest 50 years of any in the past 12,000 years (Laidre, 2005). The amount of ground which is permanently frozen (permafrost) has decreased globally by 30% since 1900 (Blatt, 2005). The thickness of ice in Greenland is decreasing by about 3 feet a year. All the glaciers of Glacier National Park in the United States are expected to disappear in this century (Blatt, 2005). About 85% of the snowfields in the Western U.S. have decreased their volume since the 1950s. The famous snows of Mt. Kilimanjaro in Africa may be gone by the years 2010-2020. This mountain has already lost glaciers which were once thousands of feet thick. Mt Everest is 4 feet shorter than it once was and its glacier has retreated three miles. The Eastern Himalayas have lost 20% of their glaciers in the past century and all the glaciers may be gone by the year 2035. In some areas, the glaciers retreat 500 feet per year (Bowen, 2005).

ESTIMATED VOLUME OF NORTH AMERICAN ICE VOLUME IN PAST 140,000 YEARS

--after Lambeck, 2001

CHART

--after Gore, 2006

3) ANTARCTIC ICE IS MELTING

Increases in temperature and the salinity variations have been reported from deep water off Antarctica (Smedsrud, 2005). Both the amount of Arctic and Antarctic ice is decreasing. Sometimes large pieces of ice break free such as a 48 mile x 22 mile piece of Antarctic ice in 1995. In March 2002, an ice area of more than 12,500 km 2 collapsed from the Larsen B Antarctic ice shelf (Domack, 2005). In Antarctica, the ice sheets of Western Antarctica are much more vulnerable to change than those in the eastern half, given nature of the terrain below the ice. In the past 25 years, the amount of annual ice over the Arctic ocean has decreased by 3% per decade (Laidre, 2005).

4) ARCTIC ICE IS MELTING

In the past 25 years, the amount of annual ice over the Arctic ocean has decreased by 3% per decade (Laidre, 2005). Within 50 years, the amount of Arctic ice during summers may be sufficiently reduced to allow shipping through the Arctic (Speth, 2004; Blatt, 2005).

5) GREENLAND ICE IS MELTING

Greenland ice is melting and becoming less stable.

6) SEA LEVELS ARE RISING

Because of this melting ice all over the world, sea level is rising. Note that sea levels are approaching their highest point in the past 140 thousand years in recent history.

--after Lambeck, 2001

1. Would your views on global warming be changed if you lived closer to the ocean? How would you view efforts to curb carbon dioxide emissions?
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