Grounding Line Location using Echograms - CReSIS

TEACHER PAGE – Trial Version
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Lesson Title: Data Series – Grounding Line Location using Echograms
Grade: 9-12
Question: How do scientists use radar track and understand a glacier’s motion over time?
Time:
45 – 60 minutes (plus additional time for instruction of echogram interpretation)
Scope of the Lesson:
This lesson explores the use of radar for the purposes of analyzing the health and movement of glaciers over time.
Students will label, interpret and understand surface and grounding line changes over time. This lesson will likely be an
introduction to radar and glaciers, as well as the interpretation of the 2D graphics produced (echograms). Basic physics
principles of the electromagnetic spectrum will be explored and put into the context of polar science and glaciology.
Objectives:
Given a set of data students will be able to:
• Identify grounding lines of a glacier for several years of data
• Plot data that is collected from echograms
• Use latitude and longitude to identify direction
• Understand the reason for the change in grounding lines over time
Standards:
• National 9-12: A1, 2, 3, 4, 5; B1, 2; C2, 4; E1; F1, 2; G6;
Vocabulary:
• echogram: 2D image created from radar signals detected from the return signal after of the snow surface and
bedrock
• glacier: an accumulation of ice, snow, water, rock, and sediment that moves under the influence of gravity
• grounding line: location where a glacier moves off the bedrock and begins to float on water
• ice sheet: large sheet of ice and snow that covers an entire region of land (50,000 km 2 , 20,000 mi 2 ) and spreads
out under its own weight
• Multichannel Coherent Radar Depth Sounder (MCoRDS): radar with frequencies specific for detection of the
snow surface and travel through the ice to the bedrock
• outlet glacier: glacier which drains an inland ice sheet or ice cap and flows to the open water
• Radio Detection and Ranging (Radar): a portion of the electromagnetic spectrum with low frequencies and long
wavelengths
• remote sensing: acquisition of information about an object or substance without direct physical contact
o Active sensors emit radiation which is directed toward a target. The signal reflected from that target is
detected and measured by the sensor.
o Passive sensors are used to measure energy that is naturally available.

Background:
Ice sheets, such as those found in Greenland and Antarctica play an important role in a number of Earth systems. CReSIS
is especially interested in their role of changing sea levels. An ice sheet is formed when large amounts of snow
accumulate over time, and under its own weight begins to compress into ice and spread out over the land. In some cases
this ice is trapped by come geologic features such as a mountain range. In other cases, this ice is able to flow through
breaks in these mountains, flowing through valleys as glaciers, and eventually reaching the open water. These are called
outlet glaciers, and are the primary way ice from the interior of an ice sheet reaches the ocean. Through information
about ice thickness and where the ice begins to float as it approaches the ocean (the grounding line), it is possible gain
knowledge about the amount of water displaced from the ice and its role in sea level changes (Figure 1). CReSIS is
generally interested in the ice thickness and location of the grounding line
for the purposes modeling sea level rise. Depending on how much ice exists
and how quickly it is reaching the ocean, it is possible to estimate how
much sea level may change in the future.
Figure 1 - Illustration showing various stages of a
grounded glacier. The grounding line is the location
where the bedrock, bottom of the glacier, and
water meet.
CReSIS measures ice sheet thickness by flying radar sensors mostly over
regions of Antarctica and Greenland with the purpose of using the
information to better model the amount of ice on Earth and how it changes
over time. This is important in the study of glaciers, sea level rise, and
climate change. CReSIS radar data are collected via airborne platforms with
the radar attached to the wings and/or belly of an aircraft. Radar is an
active sensor in which signals are sent out (transmitted) and returned by
reflection off an object. These return signals are detected (absorbed) and
processed to produce a two-dimensional image (echogram). Echograms
contain data about locations and depths of bedrock or water under the
surface of the ice sheets. There are many types of radar that can be
attached to an aircraft depending on the science interests. The Multichannel
Coherent Radar Depth Sounder (MCoRDS) is a type of radar that is
best used for collecting information about the bedrock.
Students will interpret several echograms to locate and record the
groundling line for a glacier in Greenland. Using Google Earth, students will
plot the location of the grounding line from two different years and analyze
how the grounding line position has changed. Students will not only learn
how to interpret an echogram, but also study glacier processes and use data collected to understand why the glacier
behaved a certain way.
Materials:
• Computer with Internet and Google Earth
• Echogram Background
• Petermann Glacier (Greenland) echograms (GroundingLine_Teacher.pdf – this document contains all the
imagery discussed in this lesson along with answer keys and examples)
• Student Worksheet (optional)
Engage (for students without any glaciology background):
• CReSIS Ice, Ice Baby lessons (https://www.cresis.ku.edu/education/k-12/ice-ice-baby-lessons)
o How do Ice Sheets Form?

o How is Glacier Goo Similar to a Real Glacier?
Engage (for students with some glaciology background):
• Complete an Internet search for glacier and ice sheet images
• Make a few predictions about glacial processes (formation, movement, etc.)
Q1) Sketch a glacier and label several parts.
Q2) What part of a glacier do you predict to flow the fastest? What may cause a glacier to speed up?
Q3) Give an example of a method or technology that researchers use to collect data about glaciers.
Explain:
Explore the ‘Echogram Background’ document. Make sure you are familiar with all the necessary information.
• Discuss different characteristics and features of the echogram and how to interpret.
This particular echogram was from the 2003 Greenland field campaign flown over Petermann Glacier in NW Greenland.
Q4) What characteristics of a glacier do you see in this echogram?
Q5) Describe how are you able to identify each characteristic?
Q6) Estimate the latitude and longitude of the grounding line.
Q7) What direction is the platform carrying the radar flying?
Explore:
• Using the Petermann Glacier echograms (PDF), first estimate the
approximate location of the groundling line from each of the two
2003 images and record in Table 1. Plot these coordinates in Google
Earth (Figure 2).
• Draw a line across the glacier connecting the two points of your
estimated grounding line.
• Plot the coordinates from the x-axis of the echogram and
determine which direction the plane was flying and record in Table
1. Make sure to carefully label the points from each echogram so as to not confuse them with other years.
• Repeat for each of the two 2007 images. You should have a total of 28 coordinates plotted.
Table 1 - Fill in coordinates for estimated grounding line locations.
2003 A
2003 B
2007 A
2007 B
Figure 2 - Coordinates from 2003A plotted in
Google Earth.
Latitude Longitude Flight Direction

Q8) Do the grounding lines fall between the flight lines? If not recalculate your estimated grounding line
Q9) Briefly describe the changes you observe in the location of the grounding line in 2003, 2007.
Q10) Briefly explain how you determined the flight path direction for the data collected for each echogram.
*NOTE* A *.kmz (Google Earth) file has been included with all of the data points plotted for your reference. It also
includes estimated grounding lines drawn for each of the three years (2003, 2007, and 2011).
Explain:
Display the scientist’s estimations for the grounding
line (Figure 3) and have students compare their results.
The most common error will be drawing the actual line
connecting the grounding line points. Because
grounding line interpretations are only an estimate
from the echogram (using only two echograms
resulting in two estimates of position), this step is
subject to a fairly high degree of error due to personal
analysis. As long as there is a difference in the
grounding line positions between 2003 and 2007 and
the 2007 line is located to the NW (above and to the
left) of the 2003 line, then the result is acceptable for
further discussion.
Q11) Does the location of your estimated grounding
lines look the same as the Petermann Glacier
Grounding Line Map (Figure 3)? If not, what are some
possible sources of error?
Q12) Why would it be important for researchers to record this type of data over several years?
Extend:
Figure 3 - Scientists accepted grounding line locations from 2003 and 2007
echogram data.
• The migration of grounding lines provides some indication of the stability and health of a glacier; if it is
advancing, the glacier is getting thicker and growing; if the grounding line is retreating, the glacier is thinning
and likely accelerating.
• Glaciers that have recently accelerated and thinned are transporting more ice into the ocean with grounding
lines that are migrating inland (retreating).
The northern part of Petermann Glacier experienced many dramatic changes in 2009 and 2010. Scientists have recorded
images or video of the great glacier break-off from August 2010.
• View the following videos related to Petermann Glacier.
o Byrd Polar Research Center: http://bprc.osu.edu/wiki/Petermann_Glacier_before-after-photos_2010-
2011
o Discovery News: http://news.discovery.com/videos/news-arctic-melt-caught-on-video.html
o Earth Observatory: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=45112
• Recently processed 2011 data is now available on the CReSIS web site. A couple of images have been included
on the ‘Petermann Glacier’ PDF.

• Go through the same processes outlined above to determine the grounding line in 2011.
Q13) How has the grounding line changed position since 2007? 2003?
Evaluate:
Provide a copy of a blank echogram (Figure 4) and have the students respond to the following questions/tasks.
• Using a blank echogram, respond to the following questions/tasks:
Q14) Trace and describe the snow surface and bedrock echo lines.
Q15) Approximate the grounding line latitude and longitude and draw it on the echogram.
Q16) Describe the general flight path of the plane over the glacier and the physical features of the glacier along this
path.
Q17) Suggest why an echogram would be important to a glaciologist.
Related Activities:
• Data Series – Ice Thickness (https://www.cresis.ku.edu/education/k-12/online-data-portal)
Resources:
Center for Remote Sensing of Ice Sheets. 2011. Data Products. https://data.cresis.ku.edu/data/rds/.

STUDENT PAGE
Lesson Title: Data Series – Grounding Line Location using Echograms
Question: How do scientists use radar track and understand a glacier’s motion over time?
Objectives:
Given a set of data students will be able to:
• Identify grounding lines of a glacier for several years of data
• Plot data that is collected from echograms
• Use latitude and longitude to identify direction
• Understand the reason for the change in grounding lines over time
Vocabulary:
• echogram: __________________________________________________________________________________
• glacier: _____________________________________________________________________________________
• grounding line: _______________________________________________________________________________
• ice sheet: ___________________________________________________________________________________
• Multichannel Coherent Radar Depth Sounder (MCoRDS):
___________________________________________________________________________________________
• outlet glacier: ________________________________________________________________________________
• Radio Detection and Ranging (Radar):
___________________________________________________________________________________________
• remote sensing: ______________________________________________________________________________
o Active sensors _________________________________________________________________________
o Passive sensors ________________________________________________________________________
Background:
Ice sheets, such as those found in Greenland and Antarctica play an
important role in a number of Earth systems. CReSIS is especially
interested in their role of changing sea levels. An ice sheet is formed when
large amounts of snow accumulate over time, and under its own weight
begins to compress into ice and spread out over the land. In some cases
this ice is trapped by come geologic features such as a mountain range. In
other cases, this ice is able to flow through breaks in these mountains,
flowing through valleys as glaciers, and eventually reaching the open
water. These are called outlet glaciers, and are the primary way ice from
the interior of an ice sheet reaches the ocean. Through information about
ice thickness and where the ice begins to float as it approaches the ocean
(the grounding line), it is possible gain knowledge about the amount of
water displaced from the ice and its role in sea level changes. CReSIS is
generally interested in the ice thickness and location of the grounding line
for the purposes modeling sea level rise. Depending on how much ice
exists and how quickly it is reaching the ocean, it is possible to estimate
how much sea level may change in the future.
Figure 4 – Illustration showing various stages of a
grounded glacier. The grounding line is the location
where the bedrock, bottom of the glacier, and
water meet.

CReSIS measures ice sheet thickness by flying radar sensors mostly over regions of Antarctica and Greenland with the
purpose of using the information to better model the amount of ice on Earth and how it changes over time. This is
important in the study of glaciers, sea level rise, and climate change. CReSIS radar data are collected via airborne
platforms with the radar attached to the wings and/or belly of an aircraft. Radar is an active sensor in which signals are
sent out (transmitted) and returned by reflection off an object. These return signals are detected (absorbed) and
processed to produce a two-dimensional image (echogram). Echograms contain data about locations and depths of
bedrock or water under the surface of the ice sheets. There are many types of radar that can be attached to an aircraft
depending on the science interests. The Multi-channel Coherent Radar Depth Sounder (MCoRDS) is a type of radar that
is best used for collecting information about the bedrock.
Materials:
• Computer with Internet and Google Earth
• Echogram Background
• Petermann Glacier (Greenland) echograms (GroundingLine_Student.pdf)
• Student Worksheet (optional)
Engage (for students without any glaciology background):
• CReSIS Ice, Ice Baby lessons (https://www.cresis.ku.edu/education/k-12/ice-ice-baby-lessons)
o How do Ice Sheets Form?
o How is Glacier Goo Similar to a Real Glacier?
Engage (for students with some glaciology background):
• Complete an Internet search for glacier and ice sheet images
• Make a few predictions about glacial processes (formation, movement, etc.)
Q1) Sketch a glacier and label several parts.
Q2) What part of a glacier do you predict to flow the fastest? What may cause a glacier to speed up?
Q3) Give an example of a method or technology that researchers use to collect data about glaciers.
Explain:
Q4) What characteristics of a glacier do you see in this echogram?
Q5) Describe how are you able to identify each characteristic?
Q6) Estimate the latitude and longitude of the grounding line.
Q7) What direction is the platform carrying the radar flying?
Explore:
• Using the Petermann Glacier echograms (PDF), first estimate the
approximate location of the groundling line from each of the two
2003 images and record in Table 1. Plot these coordinates in Google
Earth (Figure 2).
Figure 2 – Coordinates from 2003A plotted in
Google Earth.
• Draw a line across the glacier connecting the two points of your estimated grounding line.

• Plot the coordinates from the x-axis of the echogram and determine which direction the plane was flying and
record in Table 1. Make sure to carefully label the points from each echogram so as to not confuse them with
other years.
• Repeat for each of the two 2007 images. You should have a total of 28 coordinates plotted.
Table 2 - Fill in coordinates for estimated grounding line locations.
2003 A
2003 B
2007 A
2007 B
Q8) Do the grounding lines fall between the flight lines? If
not recalculate your estimated grounding line
Q9) Briefly describe the changes you observe in the location
of the grounding line in 2003, 2007.
Q10) Briefly explain how you determined the flight direction
for the data collected for each echogram.
Explain:
Q11) Does the location of your estimated grounding lines
look the same as the Petermann Glacier Grounding Line Map
(Figure 3)? If not, what are some possible sources of error?
Q12) Why would it be important for researchers to record
this type of data over several years?
Extend:
Latitude Longitude Flight Direction
The northern part of Petermann Glacier experienced many dramatic changes in 2009 and 2010. Scientists have recorded
images or video of the great glacier break-off from August 2010.
• View the following videos related to Petermann Glacier.
o Byrd Polar Research Center: http://bprc.osu.edu/wiki/Petermann_Glacier_before-after-photos_2010-
2011
o Discovery News: http://news.discovery.com/videos/news-arctic-melt-caught-on-video.html
o Earth Observatory: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=45112
• Recently processed 2011 data is now available on the CReSIS web site. A couple of images have been included
on the ‘Petermann Glacier’ PDF.
• Go through the same processes outlined above to determine the grounding line in 2011.
Q13) How has the grounding line changed position since 2007? 2003?
Figure 3 – Scientists accepted grounding line locations from 2003 and
2007 echogram data.

Evaluate:
• Using a blank echogram, respond to the following questions/tasks:
Q14) Trace and describe the snow surface and bedrock echo lines.
Q15) Approximate the grounding line latitude and longitude and draw it on the echogram.
Q16) Describe the general flight path of the plane over the glacier and the physical features of the glacier along this
path.
Q17) Suggest why an echogram would be important to a glaciologist.

ANSWER KEY
Q1) Figure 4 is illustrates just some of the possible features students may label. Depending on their diagram, they may
have other features labeled such as moulins, crevasses, margins, ablation zone, accumulation zone, etc. Another more
complete diagram of a glacier can be obtained from Indiana University
(http://www.indiana.edu/~sierra/papers/2008/gray_clip_image002.jpg).
Figure 4 - Basic glacier features (from CReSIS 'Glaciers in Motion' project)
Q2) Answers will vary. The center part of the glacier should flow the fastest as there is less friction with the margins or
sides of the glaciers (mountains). A glacier may speed up if the surface slope changes or if water reaches the bed and
helps to reduce friction between the bottom of the glacier and the bedrock.
Q3) Researchers can use a variety of technologies from GPS units placed on the actual glacier to monitor motion to the
radar technologies mentioned in the background of this lesson. For radar, electromagnetic signals are sent from an
airborne platform and the reflections from various surfaces (snow surface, bedrock, water, etc.) are detected.
Q4) This echogram illustrates the snow surface, bedrock, ice, water, and the grounding line. You can also see the
coordinates along the flight path indicating the direction of flight.
Q5) The snow surface is the initial reflection. The bedrock is the dark reflection towards the middle to bottom of the
echogram, visible underneath the snow surface line. This is typically more jagged than the snow surface. The grounding
line can be determined as the location where the bedrock echo is distorted and blurry by the reflection of the radar
signal by water.
Q6) ~80.5° N, 60.4° W. The coordinates should fall between 80.407° N and 80.605° N, and 59.754° W and 60.759° W.
Q7) The plane is flying to the northwest, from the interior of Greenland, along Petermann Glacier.

Table 3 - Approximation of estimated grounding line coordinates.
Latitude Longitude Flight Direction
2003 A 80.55° N 59.90° W NW
2003 B 80.57° N 59.80° W SE
2007 A 80.58° N 59.89° W NW
2007 B 80.60° N 60.05° W SE
Q8) The coordinates for the grounding line should fall between the coordinates plotted from the x-axis of the echogram.
See Figure 5 for the data from 2003 A.
Figure 5 - Estimated grounding line position, 2003 A
Q9) The location of the 2007 grounding line is located to the NW of the 2003 grounding line. This indicated an advance
of the grounding line, which could signify a mostly healthy glacier.

Q10) By plotting the coordinates from the x-axis of the echograms, it is possible to determine the flight path of the
plane. Also, the distance increases from the first set of coordinates to the last set, making it possible to determine flight
direction from simply plotting those two points.
Q11) Answers will vary. Accept all reasonable answers where the student accurately describes the results of their
grounding line estimations compared to the accepted location found by scientists.
Q12) Since the location of the grounding line is a rough indication of the health of a glacier, collecting this data over
multiple years will allow scientists to monitor how a glacier is behaving over time. The results of this data can also lead
to improved models to predict future changes in sea level.
Q13) The grounding line position appears to have retreated slightly since 2007, and also it has smoothed out. The line
still appears to the NW of the 2003 line. (Remember, these are estimates of grounding line position and are only based
on two samples for each year)
Figure 6 - Estimate grounding location; 2003 in green, 2007 in blue, and 2011 in orange
Q14) See Figure 7

Q15) See Figure 7
Figure 7 - Diagram labels for questions 14 and 15
Q16) The plane is flying to the NW from the interior of Greenland across Petermann Glacier. The glacier is getting
thinner as the plane moves to the northwest and moves closer to the open water. This it to be expected as glaciers are
thickest near the interior and thin as you move towards the terminus.
Q17) Refer to question 12.