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Ice Sheets and Sea Level Rise

The ice sheets of Greenland and Antarctica contain massive amounts of frozen water (i.e., ice) that, if broken off or melted, for instance from extended global warming or from outward ice flow, would go largely into the oceans. In view of the vast size of the oceans, covering over 70% of the Earth’s surface area, many people might at first think that the addition of ice or melted ice from the ice sheets would have little impact on global sea level. The numbers prove otherwise, however, and doing the calculations helps to instill this fact as well as recognition of the vast size of the Earth’s two major ice sheets. The Antarctic ice sheet, for instance, has an area far exceeding the area of the United States, and over sizable regions its ice extends to a depth of greater than 2 miles (3.2 kilometers).

Grade Level: Middle School (6-8)
Curriculum Topic Benchmarks: M1.3.2, M1.4.2, S1.3.2, S2.4.1
Subject Keywords: Ice sheets, Sea level rise

Author(s): Claire L. Parkinson
PUMAS ID: 02_10_97_1
Date Received: 1997-02-10
Date Revised: 1999-05-17
Date Accepted: 1997-05-09

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Comments

Comment by Donald P. Wylie on May 13, 1999
"Interesting example. Regarding the comment at the end that coast lines are not vertical so the estimate of sea level rise is less than calculated, there is a way to estimate a minimum amount of sea level rise. The earth has only 25% of its surface in land above water. If the melted ice sheets covered all land, than the calculation of sea level rise would be reduced by 75%. So the predicted ~80 meter rise in sea level would be ~60 meter if all of the earth's surface were covered with ocean. Therefore, the sea level rise estimate is between 60 and 80 meters. Even 60 meters is a lot in my book.

Author's Response: The suggestion made by Donald Wylie is very nice. Elaborating on it, I suggest the following: A lower bound to the amount of sea level rise can readily be estimated by conceptually spreading the water from the ice sheets over the entire globe instead of just over the ocean area of the globe. When this is done, the minimum global sea level rise from the Greenland ice sheet would be (2,343,728 cubic kilometers)/(surface area of the Earth) and that from the Antarctic ice sheet would be (26,384,368 cubic kilometers)/(surface area of the Earth). Inserting the 510,073,000 square kilometer surface area of the globe from the "Hammond Citation World Atlas" (Hammond, Maplewood, New Jersey, 1992, p.352), the results are lower bounds of 4.6 meters of sea level rise from the Greenland ice sheet and 51.7 meters of sea level rise from the Antarctic ice sheet, for a total of 56.3 meters of sea level rise from both ice sheets together."

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