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Simulation Analysis of Glacial Surging in the Des Moines Ice Lobe The Proceedings of the International Conference on Creationism Volume 6 Print Reference: Pages 263-273 Article 24 2008 Simulation Analysis of Glacial Surging in the Des Moines Ice Lobe Jesse A. Sherburn Mark F. Horstemeyer Kiran Solanki Follow this and additional works at: https://digitalcommons.cedarville.edu/icc_proceedings DigitalCommons@Cedarville provides a publication platform for fully open access journals, which means that all articles are available on the Internet to all users immediately upon publication. However, the opinions and sentiments expressed by the authors of articles published in our journals do not necessarily indicate the endorsement or reflect the views of DigitalCommons@Cedarville, the Centennial Library, or Cedarville University and its employees. The authors are solely responsible for the content of their work. Please address questions to [email protected]. Browse the contents of this volume of The Proceedings of the International Conference on Creationism. Recommended Citation Sherburn, Jesse A.; Horstemeyer, Mark F.; and Solanki, Kiran (2008) "Simulation Analysis of Glacial Surging in the Des Moines Ice Lobe," The Proceedings of the International Conference on Creationism: Vol. 6 , Article 24. Available at: https://digitalcommons.cedarville.edu/icc_proceedings/vol6/iss1/24 In A. A. Snelling (Ed.) (2008). Proceedings of the Sixth International Conference on Creationism (pp. 263–273). Pittsburgh, PA: Creation Science Fellowship and Dallas, TX: Institute for Creation Research. Simulation Analysis of Glacial Surging in the Des Moines Ice Lobe Jesse A. Sherburn, M. S., 203 John Wesley Road, Starkville, MS 39759 Mark F. Horstemeyer, Ph. D., 1292 Chapel Hill Road, Starkville, MS 39759 Kiran Solanki, M. S., 1030 North Montgomery St. Apt. E, Starkville, MS 39759 Abstract We analyze the Des Moines Ice Lobe of the Laurentide Ice Sheet (a main portion of the glacier that fl owed into the United States) using fi nite element simulations to explore plausible surging scenarios that can reduce ice motion time scales from thousands of years to a couple of decades. We chose the Des Moines Ice Lobe of the Laurentide Ice Sheet, because of its relatively simple geometry. Previous studies considered idealized geometries of continental scale to investigate parameters related to the surging phenomena (cf., Horstemeyer & Gullett, 2003). These continental scale simulations of the Laurentide Ice Sheet provide boundary conditions for our local scale fi nite element simulations to allow us to examine effects of varying precipitation rates on the larger ice sheet. To further the work of Horstemeyer and Gullett, we performed three dimensional simulations, added a deformable basal till layer, and modifi ed the problem domain from a generic dome to a slab representing the front edge of the Des Moines Ice Lobe. These three dimensional simulation results illustrate clear surging lobing effects that have been observed in nature. Keywords Glacier, Surging, Material modeling, Internal state variable, Des Moines Ice Lobe Introduction associated with the uniformitarian paradigm. Not In contrast to the uniformitarian paradigm of that uniformitarians do not recognize these higher multiple ice ages, Oard (1990) and Vardiman (1994, frequency seasonal surges, but they argue for lower 1996, 1997), based a biblical frame of reference, have frequency ones as well. When a surge has a large advocated a single ice age following the catastrophic amplitude, they call it an ice age. Our calculations global Genesis Flood. These authors argue that warm show that, both large and small amplitude surges can post-Flood oceans at the mid and high latitudes occur on time scales consistent with the creationist together with high levels of volcanic ash and aerosols paradigm. Oard (1990) and Vardiman (1994, 1996, induced a post-Flood ice age. Subsequent cooling of 1997) provide a framework for this understanding of the oceans and decrease in post-Flood volcanism, glacial dynamics. in turn, led to the termination of the ice age. In Oard’s estimates of average ocean temperature a mathematical sense, an abrupt rise in ocean and ice volume since the Flood can be divided into temperature resulting from the catastrophic Flood the following fi ve intervals: (a) immediate post-Flood caused high levels of precipitation and ice sheet period, (b) ice build-up period, (c) maximum glaciation growth in the high latitudes. This ocean temperature period, (d) glacial retreat, and (e) equilibrium. anomaly decreased in a nonlinear fashion to yield Although surging and retreat can occur periodically our present day climate. However, interspersed within a year during the different seasons, the periods within this nonlinear decrease in temperature were mentioned here have the mean global averages of oscillations that arose from fl uctuations in seasonal glacial ice in view. Our simulation study does not temperature. distinguish between glacier or ice sheet, because the From an uniformitarian perspective, one of the varying parameters can represent either a glacier or primary arguments for multiple ice ages is evidence ice sheet. For simplicity, we shall henceforth use the for multiple surges in the main ice sheets. Clearly, term glacier for both. the evidence does point to multiple surges. Surging Horstemeyer and Gullett (2003) were the fi rst to is basically high rate glacial motion. In fact, multiple analyze the mechanics of glacial surging in terms of a surging occurs in modern glaciers during the different biblical understanding of earth history. They studied seasons as the temperature cycles. The frequency certain parameters related to material properties and of these surges however is much higher than those environmental conditions as derived from modern 264 J. A. Sherburn, M. F. Horstemeyer, & K. Solanki ice shelf Clarke (1997) assumed the leading edge to have a Labrador Sea velocity of 41 m/yr. A temperature gradient existed e divide ide divide div through the vertical thickness ranging from –42° C saddl to 0° C. The surge and quiescent periods of the divide DOME Laurentide Ice Sheet were 0.48–19.15 km/yr and K divide e divide ew a tin 0.11–3.26 km/yr, respectively, in the Marshall and D i Laurentide v i d Ic Cordilleran e Clarke (1997) simulations. Their results support dle or sad ad Ice Sheet Labr de DOME Divi the plausibility of internally generated instabilities Hud e sSheeton Divide (MacAyeal, 1993a, b; Payne, 1995) that induced the divide surges, and the amplitudes depended upon the ice dynamics and initial temperature confi guration. Heinrich events in the Laurentide Ice Sheet have Minn. been claimed to produce abnormal iceberg production Des Jam and surging events. To describe a Heinrich event, Lobe Moi e s nes Lob Verbitsky and Saltzman (1995) developed a scaling e law that has basal melting as the mechanism to Figure 1. Laurentide Ice Sheet and location of Des induce surging and streaming of the ice. The high rate Moines Ice Lobe. velocities depend upon the physical properties of the ice sheet, the magnitude of the geothermal heating, laboratory studies and fi eld investigations. The goal the magnitude of frictional heating, and the elevation was to elucidate possibilities of high ice fl ow rates of the ice sheet. based upon several parameters: ice/snow material This study simulates the possibility of glacial behavior with its microstructure/inclusion features, surging in the Des Moines Ice Lobe from a creationist ice/snow accumulation rates and boundary conditions, time frame. In the following section, we discuss the temperature effects of the ice/snow pack, geometry of literature involving the Des Moines Ice Lobe. Then the glacier, and the ice/ground interfaces. Their work we describe the setup of the fi nite element simulations showed that the rapid advancement of a glacier, known of part of the Des Moines Ice Lobe. The boundary as surging, could be applied to the post-Flood setting conditions for the simulations are taken from the and the biblical time frame, provided precipitation previous work by Horstemeyer and Gullett (2003) rates were suffi ciently high. This work also identifi ed who focused on a continental scale analysis similar the most important parameters involved with glacial to the large Laurentide Ice Sheet. The boundary surging, namely, precipitation rate, ice-ground conditions for the Des Moines Ice Lobe are varied interaction, and material behavior. The Horstemeyer for a parametric study on the surging rates. We then and Gullett (2003) work did not include deformable discuss our results and offer some conclusions. till beneath the ice. The current work investigates this feature. Des Moines Ice Lobe From an uniformitarian time frame one of the last The Des Moines Ice Lobe was a protrusion of the ice age periods was the Late Wisconsin Glaciation Laurentide Ice Sheet roughly 500 km long by 300 km period. In the Northern Hemisphere the large ice wide located in Minnesota and Iowa (Clark, 1992). Its sheet was known as the Laurentide Ice Sheet as thickness is debated in the literature. Some authors shown in Figure 1 and covered approximately an claim the lobe was up to 300 m thick (Clark), while area equivalent to the present Antarctic Ice Sheet others claim the lobe was as much as 900 m thick (Andrews, 1987). The Laurentide Ice Sheet extended (Hooyer & Iverson, 2002). The latter thickness is as far south as Illinois, Indiana, and Ohio in the problematic because till consolidation pressures United States. In some locations the ice sheet had are in confl ict with such thicknesses, and evidence small protrusions along the edges, also known as strongly suggests that the ice was thin at the edge lobes. For this study the Des Moines Ice Lobe is of the Laurentide Ice Sheet (Oard, 2004). Therefore, chosen, because of its fairly simple geometry and the we adopt the 300 m value even though the other could availability of literature data that can be used for be considered in a later study.
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