The National Snow and Ice Data Center provides our first dataset, which compares photographs of Alaskan glaciers taken decades ago to more recent photographs taken from the same vantage points. Download and open NSIDC Alaska Glacier Pair Photos.kmz. Start by clicking on the "Glacier Pairs" layer and reading the "Repeat Glacier Photographs" introduction. Then examine the photographs for each of the eleven (11) glaciers.
1. Which glaciers appear to be retreating? Which glaciers appear to be advancing? Which glaciers appear to be approximately the same in both photos?
Close the NSIDC Alaska Glacier Pair Photos.kmz and continue below.
Melting glaciers and thermal expansion are contributing to sea level rise. The current consensus scientific estimate is that sea level will rise between 20 cm and 60 cm by 2100. This range of sea level rise does not account for an increase in glacial flow rates, which may also occur with warming. Even with stabilization in greenhouse gas emissions over the next century, sea level will continue to rise due to a lag in the response of ice and water temperature to global warming. As a result, we can anticipate that over the next 100-300 years, increases in sea level are likely to surpass 1 meter (39 inches).
We will use the visualization capabilities of Google Earth to examine the impacts of 1 meter of sea level rise on several locations within the United States. Google Earth was not designed with a flexible sea level, so we need to use a few tricks to display increased sea level. It is very important that you follow these instructions closely to get the correct visualization of sea level. Please read the following text carefully.
First, we need to make sure that topography is displayed correctly. Go to Tools > Options in the Google Earth menu. Select the "3D View" tab (for a Mac, choose Google Earth > Preferences
> 3D View). Look at the options under "Terrain" (about mid-window) and make sure "Use high quality terrain" is checked and "Elevation Exaggeration" is set to "1". When you have made sure these settings are correct, click on "OK".
Open the "Sea Level Rise.kmz" file from Canvas. Overlaid images can be set at a specific elevation above sea level. Displaying an image at an elevation of 1 meter above sea level will allow us to visualize this amount of sea level rise. All elevations below or at 1 meter will be covered by the image, and all elevations above 1 meter will appear as normal. Note that setting this elevation will also include areas that are already below sea level, such as Death Valley.
Right click on the layer "1 m Sea Level Rise" and select properties. Go to the "Altitude" tab, and you will see that this layer is set at an absolute altitude of 1 meter. The layer has also been set to be partially transparent, so the land surfaces underneath the overlaid image will be visible.
Turn on the "1 m Sea Level Rise" layer if it is not already displayed. Notice that there are many places that are covered by ocean, and yet not covered by this layer. This is because Google Earth alters how it displays topography depending on how closely you zoom in to the virtual globe. To correctly visualize sea level, you will need to zoom in closely to the surface of the virtual globe.
Double click on the "New Orleans" placemark to fly to New Orleans, Louisiana. Portions of New Orleans are already below sea level, due to settling of the sediments that the city is built on. New Orleans is protected by a system of levies that keep water from the Mississippi River and Lake Pontchartrain out of the city. Even a small sea level rise may overwhelm these defenses, especially when storm surges from hurricanes are considered.
2. Urbanized land cover should be apparent because of its brighter appearance in the Google Earth base layer. Estimate the approximate percentage of urbanized land cover in the greater New Orleans area that is below 1 m elevation.
Next, double click on the "Miami" placemark to fly to Miami, Florida. All of Miami is at a low elevation. Go to the "Layers" window and turn on "3D Buildings". The identity of many structures can be by turning on the Places layer in the Layers panel. Explore the area, and answer the following question.
3. What types of economic activities in Miami would be threatened by a 1 m rise in sea level?
Florida's barrier islands, known as Keys, are also vulnerable to sea level rise. These barrier islands protect the mainland from erosion by waves and hurricane storm surges. Barrier islands are not topographically stable, and shift in response to ocean currents and sea level. Structures built on barrier islands may not survive the combination of rising sea level and changes in island topography in response to rising sea level.
Increased sea level will impact both average sea level and sea level experienced during extreme events. For example, a powerful hurricane today might produce a storm surge of 5 meters (~16 feet), meaning that the water pushed by the hurricane's winds would reach 5 meters above average sea level. The same hurricane 100-300 years from now will produce a storm surge of 5
meters above sea level in the future, leading to a total storm surge of 6 meters (~20 feet) above present day sea level.
Double click on the "Jacksonville" placemark to fly to Jacksonville, Florida. Jacksonville is at a higher elevation than Miami, but would be adversely affected by higher storm surges produced by rising sea levels. Turn off the "1 m Sea Level Rise" layer, and then turn on the "5 m Storm Surge" layer. This layer will show the approximate area flooded by a 5 m storm surge pushed up the St. Johns River by a hurricane. Next, turn off the "5 m Storm Surge" layer and turn on the "5 m Storm Surge + 1 m Sea Level Rise" layer.
4. What areas are affected by the total 6 m surge that were not affected by the 5 m surge?
Leave the "5 m Storm Surge + 1 m Sea Level Rise" layer on. This layer also represents a hypothetical 6 m sea level rise. While this amount of sea level rise is very unlikely to happen in the next few centuries, sea level may increase by 6 m on longer time scales due to long-term melting of the Greenland Ice Sheet. A 6 meter rise in sea level would have profound effects on cities around the world.
5. Locate and list 3 cities (excluding New Orleans and cities in Florida) that would be impacted by a 6 meter rise in sea level. Hypothesize how these 3 cities might be altered by this amount of sea level rise.
Attachment:- Glacial Dynamics.rar