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 a one meter (three foot) rise in average global sea level.
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.
- 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.
Stop and Think
2: Did your model support your prediction? Explain.
3: How could you make your model more accurate?
Predicting sea level rise
One of the expected effects of a warming climate is global sea level rise. The graph below shows estimated, observed, and possible future amounts of global sea level rise from 1800 to 2100, relative to the year 2000. Data from 1800-2012 come from a variety of sources:
- Red line (1800-1890): Estimated sea level change based on proxy data such as sediment records (uncertainty shown in pink).
- Blue line (1880-2009): Tide gauge data.
- Green line (1993-2012): Satellite observations.
Projections through the year 2100 are based on a statistical relationship between past rates of globally averaged temperature change and sea level rise, combined with different emissions scenarios. In general, higher emissions scenarios that lead to more warming would be expected to lead to higher amounts of sea level rise. The orange line shows the currently projected range of sea level rise most likely to occur by 2100, which falls within the larger risk-based scenario range. The large projected range reflects uncertainty about how glaciers and ice sheets will react to the warming ocean, the warming atmosphere, and changing winds and currents. Learn more here.
- Carefully examine the plot below. Then answer the Checking In and Stop and Think questions.
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 2050). 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.
3. 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.
4. 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.
5. 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.
6. As you move the slider, note changes in the map and in the information shown about how population, homes, and land are affected.
7. Click on the Facts link to open a PDF of facts and findings about the location you are exploring.
8. Prepare a short summary report about your chosen location using the information in the interactive map and facts and findings document.
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?