Case Studies

A Growing Glacier
Idaho Falls, ID

Contributed by: Mitchell Plummer, Ph.D. Staff Scientist Idaho National Engineering and Environmental Laboratory

Tecplot is used to animate simulated glacier growth in Grand Teton National Park, Wyoming. The simulation reconstructs a glacier that existed there approximately 18,000 years ago. Simulations like this help researchers gain a better understanding of past climatic changes, ultimately improving our ability to predict how increasing greenhouse gases will affect our modern climate. Sophisticated animations like this are only possible using Tecplot's advanced suite of plotting and data visualization tools.

The Engineer
Dr. Plummer is a hydrogeologist with the Geoscience Research Group at the Idaho National Engineering and Environmental Laboratory (INEEL). INEEL is a multi-program laboratory that supports the Department of Energy's (DOE) environmental quality, energy resources, science and technology, and national security endeavors.

Dr. Plummer uses Tecplot to develop animations of glacier advance and retreat in a variety of alpine areas where glacial features of past climates are well preserved. He also routinely uses Tecplot to visualize subsurface fluid flow and solute transport simulations, as the geoscience research group focuses on contaminant transport issues relevant to DOE waste disposal sites.

The Simulation
The movie illustrates a glacier growing in Grand Teton's Cascade Canyon, in response to a hypothetical 6°C climatic cooling. The simulation was developed to help determine which temperature and precipitation conditions might have produced this glacier in the northern Rockies during the last glacial maximum, approximately 18,000 year ago.

Numerical simulations like this provide a powerful tool for reconstructing climatic conditions in the geological past. Through understanding the climatic events that occurred during the transition out of the last glacial period, scientists gain greater insight into the complicated global climate system. Such knowledge helps them better understand how increasing concentrations of green house gases in the atmosphere may alter climate in the future.

Advanced numerical simulations offer several advantages over more common methods of reconstructing past climates from paleoglacial features. Simpler methods can estimate the temperature depression associated with a glacial advance, but they typically ignore several important controls on snow accumulation rates. They also provide no information about the relative extent of glaciation depending on the basin's angle to the sun.

The valley glacier that then occupied Cascade Canyon flowed well beyond the mountain front to form a lobate snout on the plain below. The glacial till deposited at the edge of the snout remained when the glacier retreated, to create a dam surrounding the depression left by the lobe. This area filled to form Jenny Lake, probably the most visited area of Grand Teton National Park.

The Data
The data sets for this animation were generated in two steps. First, a 2-D energy balance model calculated the annual snow accumulation/ablation rate that would occur under a climate approximately 6°C cooler than our existing climate.

Second, the annual snow accumulation grid is fed into a 2-D glacier flow model. This model determines the glacial shape that would evolve under specified climatic conditions. The 2-D glacier flow model writes data, at user-specified time steps, to a Tecplot-format ASCII file. The data includes ice surface elevation, ice thickness, velocity vector data, as well as Universal Transverse Mercator position and ground-surface elevation.

The final animation is created by:

1. Developing an image for the background frame. This consists of a LANDSAT image laid over a digital elevation model (DEM) of the surrounding terrain. The LANDSAT image drapes the surface by coloring the DEM surface with the LANDSAT bitmap RGB values.
2. Plotting the ice surfaces in a separate foreground frame. The contours represent ice thickness, and are colored using a white-to-blue user-defined color map.
3. Using frame linking to lock the two frame's position, scale, and view.
4. Animating the simulation time-steps that are stored as zones in Tecplot.

Tecplot
Dr. Plummer explains, "Tecplot aids my research in several ways. Perhaps the most important, and fun, aspect is that it provides the ability to observe changes in complicated systems by creating and manipulating plots with its many features."

He believes Tecplot's greatest strengths for interpreting simulation output are:

1. The ability to generate line plots and vector plots, as well as and 2- and 3-D plots from the same data set...and then plot them in a variety of frames on a single page.
2. Very fast, sophisticated, and easy-to-use 2- and 3-D exploration and manipulation tools.
3. The ease of generating complex animations that help him examine his transient 2- and 3-D data sets, as well as present his scientific findings.
4. Tecplot's ASCII file format. This format:

• does not have to be imported into a spreadsheet
• is easy to code into simulations
• is readily viewed and updated after each simulation
• incorporates parameters which can be easily manipulated within Tecplot
• allows Tecplot to quickly read data files and store plot information in binary format

Tecplot output of ice surface and velocity cross-sections at indicated positions along the glacier. The 3-D glacier surface is contoured by ice flow speed and displays flow lines.

Film and spray analysis of simulation results for a typical splash plate nozzle: the distribution of film thickness, film velocity, mean drop size, and spray flow against angle from the splash-plate centerline.

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