Spatial Analysis of Raster Data: Analyzing the Effects of Ice Removal and Sea Level Rise on the Physiography of

Antarctica

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Mark HelperJackson School of GeosciencesThe University of Texas at Austin

GIS/GPS Applications in Earth SciencesCourse and Students:

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Only GIS class in the Department Senior elective, cross listed as Grad.

Course 20 students, TA 3 hrs. lecture, 2 hrs. lab per week Prerequisite - intro. field geology with 3 hr

expose to GIS base map prep., GPS data collection

Context:

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First Lab with Raster Data Sets Previous Labs/Lectures

Data Models – raster, vector Projections Digitizing, Georeferencing ArcMap/Catalog basic

Preparation for Course Project

Raster Techniques/Tools:

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Masking Classifying and Symbolizing Hillshade and Contour Raster Calculations

Analysis Skills:

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Raster Query Strategies Highest/Lowest Elevations Elevation at a point

Raster Statistics Comparing Rasters

Raster Overlay Land vs. Water

Area and Volume Calculations Ice Sheet Properties

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Focus Questions:

Q1: What is the mean, maximum and minimum elevation of Antarctica?

Q2: What does Antarctica presently look like beneath the ice?

Q3: How much ice is there? Q4: What would a “Greenhouse”

Antarctica look like?

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Tools and Data

Tools – ArcGIS 9.x Spatial Analyst (required) 3-D Analyst (optional; area and volume

calculation)

Data – SCAR and BEDMAP sources Posted for download as ~27 Mb Zip file

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Vector Data - Coverages

Point South Pole

Arcs Continent outline Contours

Polygons Land Ice Shelves/Tongues

4.4 km

:-2.6 km

Bedrock ElevationBedrock Elevation(masked)(masked)

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Raster Data (5x5 km ESRI Grids)

4.5 km 0 m

Ice ThicknessIce Thickness

Surface ElevationSurface Elevation

4.4 km M.S.L.

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Strategy:Explore, Map, Visualize, Analyze

Explore – Raster Properties, Metadata

Map/Visualize – Overlay and Symbolize

Analyze - Query and Model

Questions basic to each step are inserted along the way

Explore the Data

Resolution Data type File size Spatial Reference Raster Stats.

e.g. Q1: What are mean, max. min. elevations?

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Explore the Data:Classify Elevations

Equal interval, 200m

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Analysis Skills:Simple Raster Calculations

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Conditional Statements and Binary Rasters

Above or Below MSLBedrock Elevation

Con([bed_elev] <= 0,1)

Map/Visualize:Q2: What does Antarctica look beneath the ice?

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Overlay binary raster with other layers and create a shoreline contour

Above or Below MSL

Bedrock Elevation

=

Final Analysis:Q4: What would “Greenhouse” Antarctica look like?

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1. Calculate new bedrock elevation raster that accounts for isostatic rise from ice removal;

2. Subtract from this new raster elevations equivalent to a higher sea level (~80 m);

3. Overlay a new binary land/sea raster

Elevation change = (Density of ice / Density of Mantle) x (ice thickness)

Final Analysis: Prepare and Compare Final Maps

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Bedrock Elevation Today Bedrock ElevationGreenhouse Conditions