Mapping Navigated Cameras| Issue Date: April - 2010, Posted On: 7/26/2010 A Shrinking Glacier: Change Detection Analyzes the Retreat of the Bering Glacier Terminus Alaa Shams |  |
 By Alaa Shams Alaa Shams is the GIS training coordinator, Louisiana Geographic Information Center, Louisiana State University; e-mail: ashams@lsu.edu. The Bering Glacier is located in coastal, south-central Alaska, bounded in the north by the St. Elias Mountains and in the south by the Gulf of Alaska. In various places, the glacier has a thickness of more than 800 meters. The glacier has an area of approximately 5,175 square kilometers and a length of 190 kilometers. It covers 6 percent of Alaska’s glacier cover area. It’s also the largest surging glacier in North America; the last surge occurred from 1993-1995. Today, the Bering Glacier is approximately 10 to 12 kilometers shorter now than it was 100 years ago. Runoff from the glacier’s melting ice has formed Lake Vitus, which has a depth in excess of 150 meters in spots and has doubled its size since 1995, from 60 square kilometers to more than 120 square kilometers. Figure 1. A snapshot of the Bering Glacier Terminus shows the latitude/longitude taken from the video stream using Red Hen GPS technology. The entire glacier lies within 100 kilometers on the Gulf of Alaska and has been spewing approximately seven cubic miles of water into the Gulf of Alaska annually, about 1.1 trillion gallons of water—twice the volume found in the Colorado River. The rapid retreat of the Bering Glacier is driven by increased ice calving, influenced by warming climatic conditions. The rapid melting rates of the Bering Glacier and others worldwide are increasing the threat of catastrophic flooding due to rising sea levels, potentially affecting coastal cities and towns across the world. Relying on New Technology The project used the Red Hen System VMS-X GPS/Video technology to fly over the Bering Glacier Terminus in 2007 and used the same system to re-fly the terminus in 2008. The system includes a mini DVD 1.4GB camera, which can collect about 30 minutes worth of recording. Figure 2. Alaa Shams prepares the Red Hen equipment and mounts the GPS/video camera in position while the helicopter pilot makes sure that it’s safe. The system is power efficient, battery operated and attached to a Garmin Geko 201 GPS receiver attached to the “hot shoe” of the digital video camera. It’s also WAAS enabled and features a 10,000-point track log with a digital compass. Figure 1 provides a snapshot of the video stream of what one GPS data point looks like for the indicated coordinate reading. The GPS has to be calibrated before each flight, and the GPS clock is synchronized with U.S. official time via Internet access and logging onto the official U.S. time Web site at www.time.gov, taking a snap shot of the computer screen with the video camera. This would then be the starting time, and it’s used to synchronize the time stamps in the tracking log file from the GPS device. Testing the Whirly Bird To determine the accuracy of using Red Hen Technology as a means of remotely accessing changes in the Bering Glacier Terminus, a Helicopter Test Flight (HTF) was made in early August 2007. The HTF pilot was instructed to fly approximately 300 meters above the Bering Glacier Terminus at a slow air speed, keeping the nose of the helicopter on its leading edge. As the HTF progressed, the Southern University Team (SU Team) simultaneously used Red Hen to continuously record GPS points and streaming digital video of the Bering Glacier Terminus. After approximately 1.5 hours, the HTF flyover of the Bering Glacier Terminus was completed, and the SU Team returned to Bering Camp. Back at the Bering camp, the SU Team downloaded the remotely sensed GPS data into the computer. Using a previously stored 2007 Landsat 7 image of the Bering Glacier’s Terminus in ArcGIS 9.2, the HTF remotely sensed GPS data were imported as a new GIS layer. Figure 3. The ice edge path from a 2007 flight was superimposed on 2007 Landsat imagery. The new HTF data layer was overlaid (superimposed) on a 2007 Landsat 7 image of the Bering Glacier Terminus. Figure 3 shows the results of the initial HTF, aimed at determining the accuracy (i.e., correspondence) of Red Hen remotely sensed GPS data to the actual Bering Glacier Terminus. The red line indicates the accuracy of the HTF flyover, during which time GPS points were remotely recorded. There was minimal deviation found in the remotely sensed GPS data when the later data layer was overlaid on a 2007 Landsat 7 image of the Bering Glacier Terminus. Refining the Scope Encouraged by this result, during one of the nightly flight-planning meetings to determine the next day’s research activity, a decision was made to re-fly the Bering Glacier Terminus to determine the extent of Bering Glacier Terminus ice edge lost from 2006 to 2007. Specifically, the primary objective was to assess ice edge lost, and then make a link between it and sea-level rise, particularly noting future impact on the Louisiana Gulf Coast. In early August 2007, the SU Team boarded the helicopter in the early afternoon and flew to the Bering Glacier Terminus. The helicopter pilot was again instructed to fly 300 meters above the Bering Glacier Terminus and hold the nose of the aircraft on its leading edge. Approximately 1.5 hours later, the re-fly plan was completed, and the helicopter returned to Bering Camp. Figure 4 is striking, because when the new 2007 GPS data layer was overlaid on a 2006 Landsat 7 image of the Bering Glacier Terminus, any ice edge found below the red line, or flight path, was interpreted as the extent of terminus retreat during the 12-month period under consideration. Further statistical calculations revealed that, during this time, the Bering Glacier Terminus retreated an average of 0.52 kilometers. But where did the lost ice edge go? Figure 4. The ice edge path from a 2007 flight was superimposed on 2006 Landsat imagery. The terminus retreat during the 12-month period is clearly visible. Through the calving process, which involves large pieces of ice edge breaking off the Bering Glacier Terminus, the 0.52 kilometers of lost ice edge fell into adjoining Vitus Lake, which is connected to the Seal River that flows into the Gulf of Alaska and into the Pacific Ocean. Robert Schuchman, lead scientist for the Michigan Tech Research Institute, estimated that approximately 30,000 cubic feet per second of water flows from Vitus Lake into the Pacific Ocean. Interestingly, the origin of this melted water is land based, which directly contributes to an expansion of the world oceans and sea-level rise. It has been previously established that a three-meter rise in the sea level of the Gulf of Mexico will cause permanent, catastrophic flooding of New Orleans, Miami and other low-lying cities along the United States’ Gulf, Atlantic and Pacific Coasts. Given this potential impact on the Louisiana economy, its coastal population and infrastructure, Michael Stubblefield, vice chancellor for Research and Strategic Initiatives at Southern University, decided to send the SU Team back to the Bering Glacier during summer 2008. The main research objective for this excursion was to determine if the 2007 findings shown in Figure 4 changed between 2007 and 2008. Figure 5. The green and red lines indicate ice-edge path change from 2007 to 2008. The research team arrived at the Bering Camp, Alaska, on Aug. 1, 2008. The following day, the helicopter, using the same flight format used during summer 2007, remotely collected GPS data as it flew low and slow over the leading ice edge of the Bering Glacier Terminus. After it returned to Bering camp, and the new GPS data were downloaded into ArcGIS 9.2. A 2006 Landsat 7 image was used as a base layer for detecting ice-edge change between 2007 and 2008. The green line in Figure 5 indicates further Bering Glacier Terminus retreat. When the 2008 GPS data layer was overlaid on top of the one for 2007 (see Figure 4), and both GPS data layers overlaid on top of the 2006 Landsat 7 image, it became apparent that a significant amount of calving took place between August 2007 and August 2008. After making a few statistical calculations, it was discovered that the ice edge lost from 2007 to 2008 amounted to an average of 0.20 kilometers, and the cumulative loss came to average 0.72 kilometers between 2006 and 2008. Thus, more land-based freshwater continued to flow through the Seal River into the Gulf of Alaska and the Pacific Ocean. High Stakes According to the United Nations Intergovernmental Panel on Climate Change, global warming is unequivocal. The observed continuous retreat of the Bering Glacier Terminus, between 2007 and 2008, is evidence of increased concentrations of carbon dioxide in Earth’s atmosphere, causing an unprecedented warming in the Polar Regions. Temperatures have warmed more than two degrees Fahrenheit in the Polar Arctic Region during the last decade. In a Wall Street Journal article on May 8, 2009, “Spring Thaw Triggers Damaging Floods in Alaska,” Jim Carlton wrote that “a spring warm-up over the past week … saw temperatures soar into the 70s—a good 20 degrees higher than normal for this time of the year.” This means Earth’s oceans are expanding due to increased melting of the Bering Glacier, and this also poses a major challenge for policymakers, given the large numbers of people in the United States and worldwide, including infrastructure, who are currently at risk for permanent coastal flooding and other catastrophic events similar to Hurricanes Katrina and Rita that devastated New Orleans and portions of the Louisiana and Texas Coasts in 2005. The Bering Glacier now contributes approximately 30,000 cubic feet per second of land-based freshwater to sea-level rise daily. Certain adverse conditions such as stronger hurricanes, more frequent tornadoes and coastal flooding will continue to occur due the amount of carbon dioxide already released into Earth’s atmosphere. However, there’s still time for policymakers to intervene now to reduce regional and global impacts of climate change that are projected to worsen by 2030 if nothing is done to curtail consumer behavior, reduce our reliance on fossil fuels and place more emphasis on the development of a “Green World,” characterized by alternative fuel use, housing and transportation. Author’s Note: I’d like to thank Robert Schuchman and Liza Jenkins from Michigan Tech Research Institue for the Landsat imagery as well as Scott Guyer from the BLM Alaska State Office and the Bering Glacier camp manager from 2007 to 2008. The 2008 Southern Team consisted of Marcus Bonton, Revathi Hines, Shekeitra Lockhart, Corey Loyd, Lionel Lyles, Alaa Shams, Jeremy Swan, Essie Thibodeaux, Courtney Thompson and Derkirra Wilkerson. The 2007 Southern Team consisted of Michael Stubblefield, Pamela Brue, Mykel Delandro, Revathi Hines, Jacquole Landry, Lionel Lyles and Alaa Shams. | |
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