Mapping Ice Melt Extent in Greenland between 1979-2007 Using ArcGIS

Elizabeth Crook, University of California-Irvine
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Summary

This activity introduces students to Greenland ice-melt data derived from passive microwave remote sensing between the years 1979 and 2007. Students make a quantitative comparison between the two years using the mapping program ArcGIS. Students are provided with NASA raster images in GeoTiff form that show Greenland ice melt extent over two of the years on record (1979 ad 2007). Students then draw polygons over these raster files and calculate a change in area between the years on record. While tools exist in ArcGIS to quantify the extent of ice melt using the raster images themselves, drawing polygons is an important and often little-practiced skill in ArcGIS, and is therefore the focus of this activity. This activity can also be modified for more advanced map-makers working with raster files, who need practice using additional tools in the Arc Toolbox. However, raster calculations are not generally a skill covered in an introductory GIS course.

The activity is meant to reinforce important map-making skills (like drawing polygons and creating new geodatabases) using a data set that explores a real-world application of ArcGIS for Earth Science students. While any two (or more!) years on record can be used, 1979 and 2007 have been used to explore extremes in the data. You can learn more about the data set and the GeoTiff images here: http://nsidc.org/greenland-today/. The activity was designed for students with prior mapping skills, but can be modified for those who have little to no mapping experience (step by step instructions can be provided, upon request).

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Context

Audience

This activity has been used as a lab in an upper-division, introductory ArcGIS course for Earth System Science majors. Students typically have prior knowledge of mapping skills and are familiar with the ArcGIS program and much of the required language. The activity is designed to practice/reinforce how to create polygons, edit layers, and create geodatabases using ArcGIS. The activity works best for reinforcing skills learned in Arc with an emphasis on students who are looking for ways in which ArcGIS can be applicable to Earth Science majors. This particular activity, which uses the years 1979 and 2007, can be modified to use any of the current years on record using the following NASA website: http://nsidc.org/greenland-today/.

Skills and concepts that students must have mastered

Basic knowledge of ArcGIS mapping is essential for this activity, as well as a prior knowledge of seasonal ice sheet melt and climate change. While students can be beginning mapping students, some prior knowledge of the program and its language are necessary to complete the activity. For students who are not familiar with the ArcGIS editing toolbox, this activity should follow a tutorial on how to complete the necessary skills to complete the activity. The activity is a great way to reinforce concepts covered in class/lab and can therefore be a stand-alone supplementary lab assignment or homework.

How the activity is situated in the course

In the course that this activity is provided, it is a post-lab assignment in which students must reinforce concepts learned in lecture/lab.. The activity is a standalone assignment designed to pull together many skills learned in a GIS course, and often occurs in week 6 or 7 of a 10 week introductory course. Students are given a background lecture on creating polygons, and the usefulness of this skill is demonstrated. Students then will complete a lab on polygons before having to synthesize this assignment unaided.

Goals

Content/concepts goals for this activity

Students should be able to map annual ice melt data and quantify changes in ice sheet melt extent between the years 1979 and 2007 using tools available in the program ArcGIS.

Higher order thinking skills goals for this activity

Students should be able to connect skills learned in a mapping program to climate change analysis and annual ice sheet surface melt extent. This enables students to more readily transfer skills learned into real-world applications that they may find in graduate studies or when working in an Earth Science related field. Synthesis of data is a higher order skill that is not often practiced, even at the college level.

Other skills goals for this activity

Description and Teaching Materials

This activity should be done independently and could take anywhere from 2-4 hours to complete, depending on student skill level and speed.
Students are first asked to read the introduction to the worksheet and explore the website from which the data is found. Students then download all appropriate data and proceed with the activity as stated on the activity worksheet, depending on their skill level.

When completed, students should have a PDF of each map they created, as well as a calculation for how much sea ice extent has changed over the last 40 years. To make the analysis more advanced, students can report their ice sheet cover and a class average can be calculated and compared to recent scientific analysis on the Greenland Ice Sheet (http://nsidc.org/greenland-today/). An analysis of why the class estimates may differ from the NASA estimates would help solidify understanding of the limitations of drawing polygons when mapping. If students are more advanced, they can then practice the same activity using the rasters provided and compare their polygon calculations to the raster calculations.

Student Handout (Microsoft Word 2007 (.docx) 153kB Sep12 18)
Mapping Materials (Zip Archive 283kB Sep12 18)

Teaching Notes and Tips

This mapping activity is meant to address a unique and targeted skill in GIS mapping software, rather than to accurately depict ice melt extent through time. Students are meant to draw parallels between skills learned in a mapping course and their relationship to real world applications.

(Please note: there are no step by step instructions on how to draw polygons, etc in ArcGIS. If you require additional instructions for your students, please contact the author of this assignment using the contact details on the SERC website).


Assessment

Assessment is based on the final map PDFs provided by the student and the numbers they have calculated based on the changes in area of their surface melt polygons. Numbers will vary by student, but should generally be within a 10% range of one another. An analysis of what may account for such wide variation in these numbers would be a good way to think about map scale, resolution, and the limitations of polygons in analysis.

References and Resources

All materials for this activity were taken from the National Snow and Ice Data Center (NSIDC) at NASA: http://nsidc.org/greenland-today/