Grounding Line Location using Echograms - CReSIS

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ANSWER KEY Q1) Figure 4 is illustrates just some of the possible features students may label. Depending on their diagram, they may have other features labeled such as moulins, crevasses, margins, ablation zone, accumulation zone, etc. Another more complete diagram of a glacier can be obtained from Indiana University (http://www.indiana.edu/~sierra/papers/2008/gray_clip_image002.jpg). Figure 4 - Basic glacier features (from <strong>CReSIS</strong> 'Glaciers in Motion' project) Q2) Answers will vary. The center part of the glacier should flow the fastest as there is less friction with the margins or sides of the glaciers (mountains). A glacier may speed up if the surface slope changes or if water reaches the bed and helps to reduce friction between the bottom of the glacier and the bedrock. Q3) Researchers can use a variety of technologies from GPS units placed on the actual glacier to monitor motion to the radar technologies mentioned in the background of this lesson. For radar, electromagnetic signals are sent from an airborne platform and the reflections from various surfaces (snow surface, bedrock, water, etc.) are detected. Q4) This echogram illustrates the snow surface, bedrock, ice, water, and the grounding line. You can also see the coordinates along the flight path indicating the direction of flight. Q5) The snow surface is the initial reflection. The bedrock is the dark reflection towards the middle to bottom of the echogram, visible underneath the snow surface line. This is typically more jagged than the snow surface. The grounding line can be determined as the location where the bedrock echo is distorted and blurry by the reflection of the radar signal by water. Q6) ~80.5° N, 60.4° W. The coordinates should fall between 80.407° N and 80.605° N, and 59.754° W and 60.759° W. Q7) The plane is flying to the northwest, from the interior of Greenland, along Petermann Glacier.
Table 3 - Approximation of estimated grounding line coordinates. Latitude Longitude Flight Direction 2003 A 80.55° N 59.90° W NW 2003 B 80.57° N 59.80° W SE 2007 A 80.58° N 59.89° W NW 2007 B 80.60° N 60.05° W SE Q8) The coordinates for the grounding line should fall between the coordinates plotted from the x-axis of the echogram. See Figure 5 for the data from 2003 A. Figure 5 - Estimated grounding line position, 2003 A Q9) The location of the 2007 grounding line is located to the NW of the 2003 grounding line. This indicated an advance of the grounding line, which could signify a mostly healthy glacier.
Page 1 and 2: TEACHER PAGE - Trial Version * Afte
Page 3 and 4: o How is Glacier Goo Similar to a R
Page 5 and 6: • Go through the same processes o
Page 7 and 8: CReSIS measures ice sheet thickness
Page 9: Evaluate: • Using a blank echogra
Page 13: Q15) See Figure 7 Figure 7 - Diagra

Grounding Line Location using Echograms - CReSIS

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