dxdQ (m/Wm-2) = 1.77e4 Time Specs: From: -300 To: 0 DT: 0.2 Integration Method: Runge-Kutta 4 Now, the changing summer insolation due to orbital variations will force the grounding line position to move back and forth. Higher insolation pushes the grounding line position to the north (toward more negative values, while a decrease in insolation moves the grounding line to the south (more positive values). As you should know by now, moving the grounding line position will cause the glacier to advance and retreat. Run the model and study the results by plotting key parameters together. a) First, study the relationship between the Qt (the insolation over time) and the grounding line position (in km) — what is the general relationship? Do the peaks and troughs of both curves match up as you would expect? What is the typical period of oscillation in the grounding line position? Paste in a graph as part of your answer. b) How does the length of the ice sheet respond to changes in the grounding line position? How do the peaks and troughs of these two parameters compare, and is it as you expected? Paste in a graph as part of your answer. In articulating your answer, you should consider the response time of the ice sheet you figured out earlier and compare it to the period of oscillation in the grounding line position. c) What is the lag time in kyr of the ice sheet relative to the grounding line? How consistent is this lag time? d) What is the range of variation in the length of the glacier in km? Compare it to the Laurentide Ice Sheet, which expanded and contracted about 20° of latitude from its center of mass (x = 0); there are 111 km per degree of latitude. 18O e) Now compare the ice sheet length with the SPECMAP record of from marine 18O sediments. SPECMAP is partly a measure of ice volume and partly a measure of temperature — higher values represent more ice and colder temperatures. How well do they agree? How similar or dissimilar are the times of the peaks and troughs? Consider whether ice sheets exhibit primarily linear or non-linear behavior, and use this to comment on the probable reason(s) for any similarity or difference between the model and the SPECMAP curve.
dxdQ (m/Wm-2) = 1.77e4 Time Specs: From: -300 To: 0 DT: 0.2 Integration Method: Runge-Kutta 4 Now, the changing summer insolation due to orbital variations will force the grounding line position to move back and forth. Higher insolation pushes the grounding line position to the north (toward more negative values, while a decrease in insolation moves the grounding line to the south (more positive values). As you should know by now, moving the grounding line position will cause the glacier to advance and retreat. Run the model and study the results by plotting key parameters together. a) First, study the relationship between the Qt (the insolation over time) and the grounding line position (in km) — what is the general relationship? Do the peaks and troughs of both curves match up as you would expect? What is the typical period of oscillation in the grounding line position? Paste in a graph as part of your answer. b) How does the length of the ice sheet respond to changes in the grounding line position? How do the peaks and troughs of these two parameters compare, and is it as you expected? Paste in a graph as part of your answer. In articulating your answer, you should consider the response time of the ice sheet you figured out earlier and compare it to the period of oscillation in the grounding line position. c) What is the lag time in kyr of the ice sheet relative to the grounding line? How consistent is this lag time? d) What is the range of variation in the length of the glacier in km? Compare it to the Laurentide Ice Sheet, which expanded and contracted about 20° of latitude from its center of mass (x = 0); there are 111 km per degree of latitude. e) Now compare the ice sheet length with the SPECMAP record of 18O from marine sediments. SPECMAP 18O is partly a measure of ice volume and partly a measure of temperature — higher values represent more ice and colder temperatures. How well do they agree? How similar or dissimilar are the times of the peaks and troughs? Consider whether ice sheets exhibit primarily linear or non-linear behavior, and use this to comment on the probable reason(s) for any similarity or difference between the model and the SPECMAP curve.
ice_sheet_modeling_activity.v7.docx