Ice Sheets and Sea Level -- Concerns at the Coast (Student Pages)

Transcription

1 STEM Ice Sheets and Sea Level -- Concerns at the Coast (Student Pages) Before you begin: 1. Think about these questions, discuss in small groups, and record your answers on your own paper. a. When you go to the beach for recreation, is the beach always the same? What kinds of changes do you notice in the shoreline? b. What controls the elevation of the sea against the shore? What causes it to go up or down over thousands of years? c. What might cause it to go up or down over days, months? Brainstorm and record some ideas for these questions: a. Why and how do ocean side city planners and coastal managers observe and measure changes in sea level? b. In what ways do businesses and the general public use and require access to coastal waters? Background Roughly 153 million Americans (~53% of the US population) live in coastal counties. World wide some 3 billion people live within 200 km of the ocean (world population in Billion). If the Greenland Ice sheet (equal to about 6 meters of global sea level) and the East and West Antarctic Ice Sheets (equal to about 64 meters of global sea level) were to melt completely, coastal areas would be flooded up to 70 meters (230 ft) above present. Geologists have determined that in the geologic past, these ice sheets have been known to melt back dramatically and sometimes even disappear during intervals when Earth s climate was warmer than it is now. With green house gases now driving us into a warmer world, our concern is to estimate how high sea level might get over the next few decades to centuries. Scientists from a number of disciplines are now focused on this issue in order to provide realistic predictions of sea level rise and inform policy makers about management in the US and throughout the world. Glaciologists, in particular, are studying physical processes happening at the base of the ice sheets and how rates of glacial flow into the sea are changing. On the other hand, ice shelves are floating ice bodies and their collapse does not contribute to sea level rise; however, they are known to buttress outlet glaciers which drain the large ice sheets into the sea. The loss of these ice sheets would have a significant impact on sea level. Moreover, atmospheric scientists are trying to narrow uncertainties in the rates of global warming, especially in the polar regions because this directly influences glacier mass balance. Objectives During this exercise you are asked to graph and analyze sea level rise over the past 20,000 years since the end of the last ice age. Given projected warming of the planet into the future and potential for sea level rise, what can we learn about how sea level rise will impact different types of coastlines? Vocabulary: Glacier mass Balance Green house effect Ice sheet Ice Shelves Outlet Glacier Tides Storm surge Coastal management Thermal expansion of water Isostasy Materials: Rulers Graph paper Pencils Objectives Students will construct graphs showing the relationship between ice sheet melting and sea level rise during the last deglaciation. the need for wise and sensible coastal A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the Climate System Research Center in conjunction with the International Polar Year

2 STEM Students will interpret the graphs to determine the rate at which sea level rose during the last deglaciation. Students will use a graph of future projections of sea level to trace the sea level displacement on three types of coastlines (this will help to assess societal vulnerability). Students can research, discuss and debate the implications and policy issues facing cities and countries with gradual sea level rise. Activities 1. Geologists have determined in a number of places around the world the former elevation of sea level over time. During the last ice age, sea level was as much as meters below present because it was otherwise taken up by precipitation to make ice sheets. Plot the sea level data in Table 1. This can be done either by hand, or by using a program such as excel to plot all the data. From this plot determine the rate of sea level rise in meters/thousand years, centimeters per hundred years and millimeters/year over the interval between 14,000 and 8,000 years ago and between 6,000 yrs ago and today. TABLE 1 Sea level rise since the Last Glaciation Sea Level Elevation (meters) Age X today Figure 1 from Stepen Rahmsdorf (2007) below contains an estimate of future sea level rise between 0.5 and 1.4 meters by the year Calculate the rate of sea level rise from this plot for both the minimum rate and maximum rates (mm/decade, for example). If you live to be 80 yrs old, by how much will sea level have risen by then. Provide a min and max range. Global mean sea level observations date A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the Climate System Research Center in conjunction with the International Polar Year

3 STEM Show your work here 3. Finally color in on the three provided maps where the shore line would be for a 1 m (~3 ft) rise of sea level as suggested by some for In a different color, show the additional areas covered by water if sea level rose by 6 m (which would take thousands of years, to melt Greenland completely). How much lateral shoreline retreat can you predict on average for each of the three map areas and what controls might there be on the rate of retreat? Analysis Think about the rates you have calculated here using average sea level data (a generic coastline) and consider the following: Does sea level rise at the same rate everywhere? What types of coastal areas are more vulnerable than others? How stable are the largest ice sheets on our planet? What knowledge is needed to decrease uncertainties in future projections? What career possibilities are there to study and mitigate coastal issues? How much more information is needed before we act? How do we best manage our coastlines as sea level rises? What choices may be necessary? Important Links (especially chapter 5) A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the Climate System Research Center in conjunction with the International Polar Year

4 Contour interval: 5 feet Topo maps available for free download at Cape Hatteras, North Carolina

5 Contour interval: 10 feet Topo maps available for free download at Siasconset (Martha s Vineyard), Massachusetts

6 Point Sur, California Contour interval: 40 m Topo maps available for free download at mile SCALE