Future of the Cryosphere
Part B: Sea Level Rise
Modeling sea level rise
The cryosphere contains a lot of frozen water. As you saw in Lab 4C, climate, the cryosphere, and the oceans are tightly connected. Relatively small changes in Earth's average temperature can dramatically increase or decrease the amount of Earth's snow, ice and liquid water. With current data trends and computer models predicting a warming climate, sea level rise has become a major concern for coastal areas. A change in average global temperature of just one degree Celsius (two degrees Fahrenheit), could result in an a one meter (three foot) rise in average global sea level.
- Using the materials provided by your instructor, design a model or experiment to demonstrate how melting sea ice and land ice contribute to sea level rise. Be prepared to share your model with the rest of the class.
- Carefully examine the plot below. Then answer the Checking In and Stop and Think questions.
- Open the Surging Seas interactive. The map pages in this interactive show threats from sea level rise and storm surge to all 3,000+ coastal towns, cities, counties and states in the continental U.S.
- Choose a location to explore that is personally important or interesting to you. Click on a state or label to get started, or type a zip code or location name in the search box at the top of the page.
- Use the Water level slider to see different risk zones associated with increasing sea level rise. The water level represents the height above average local tide. Water can reach different levels through combinations of tides, storms, and sea level rise.
- As you move the slider, note changes in the map and in the information shown about how population, homes, and land are affected.
- Click on the Facts link to open a PDF of facts and findings about the location you are exploring.
- Prepare a short summary report about your chosen location using the information in the interactive map and facts and findings document.
Stop and Think
1: Make a prediction. Which type of ice (sea ice or land ice) do you think poses a larger threat to sea level rise if large-scale melting due to climate change were to occur? Explain.
Stop and Think
2: Did your model support your prediction? Explain.
3: How could you make your model more accurate?
Predicting sea level rise
Scientists use climate models to estimate changes in future sea level rise, one of the expected effects of a warming climate. The graph below shows sea level changes predicted by six climate models, each of which ran 35 different greenhouse gas emission scenarios. The center dark region shows the predicted sea level rise for the models averaged over the 35 emission scenarios. The lighter blue region shows the range of the maximum and minimum model predictions. The outer, lightest blue section includes the uncertainties of land-ice changes, permafrost changes and sediment deposition (not including the possibility of melting of the West Antarctic Ice Sheet). The top curve is the extreme worst case scenario and the bottom curve shows the least expected change.
Stop and Think
4: According to the graph above, the range of predicted sea level rise increases with time (i.e., the range of values for the year 2100 is greater than the range for the year 2020). Explain why.
5: How might scientists improve their estimates to get a tighter range of predicted values farther into the future? Explain.
Predicting impacts of sea level rise
Global sea level and the Earth's climate are closely linked. The Earth's climate has warmed about 1°C (1.8°F) during the last 100 years. As the climate has warmed following the end of a recent cold period known as the "Little Ice Age" in the 19th century, sea level has been rising about 1 to 2 millimeters per year due to the reduction in volume of ice caps, ice fields, and mountain glaciers in addition to the thermal expansion of ocean water. If present trends continue, including an increase in global temperatures caused by increased greenhouse-gas emissions, many of the world's mountain glaciers will disappear. For example, at the current rate of melting, most glaciers will be gone from Glacier National Park, Montana, by the middle of the next century. In Iceland, about 11 percent of the island is covered by glaciers (mostly ice caps). If warming continues, Iceland's glaciers will decrease by 40 percent by 2100 and virtually disappear by 2200. Most of the current global land ice mass is located in the Antarctic and Greenland ice sheets (table 1). Complete melting of these ice sheets could lead to a sea-level rise of about 80 meters, whereas melting of all other glaciers could lead to a sea-level rise of only one-half meter.U.S. Geological Society
Estimated potential maximum sea-level rise from the melting of present-day glaciers (Poore, Williams, & Tracey, 2000)
|Location||Volume (km3)||Potential sea-level rise (m)|
|East Antarctic ice sheet||26,039,200||64.80|
|West Antarctic ice sheet||3,262,000||8.06|
|All other ice caps, ice fields, and valley glaciers||180,000||0.45|
The cryosphere has the potential to contribute an enormous amount of water to the oceans, which could cause sea level rise all over the worldeven here in the United States.
As a class, share and discuss your Surging Seas reports. Then discuss what you've learned throughout the Climate and the Cryosphere unit.
- How do climate and the cryosphere influence each other?
- How does the cryosphere impact life on Earth?