Teaching Notes

Grade Level

College undergraduates, high school students and middle school students (part 1).

Learning Goals

After completing this unit, users will be able to (examples):

  • Search for and review data and graphs related to ice coverage in the Arctic region
  • Manipulate data in a spreadsheet to produce graphs.
  • Create and interpret trendline equations to define the rate of change in temperature and ice extent
  • Compare multiple sets of time series temperature data and relate trends to changes in sea ice extent. 
  • Explain albedo and the positive feed-back mechanisms that could exacerbate climate change with continued loss of sea ice.
  • Gain familiarity with the lexicon of climate research vocabulary.

Rationale

The ice cap that covers much of the Arctic Ocean has declined significantly in recent years.  This impact of our current changing climate is often in the news and the concept and consequences of ice coverage understandable by the general public.  This module provides students with an opportunity to quantitatively explore the real changes in the polar ice cap, including the regions that have been impacted the most and the correlations between these changes and regional temperature variation.  The Arctic region has seen the most substantial temperature increases thus far and are expected to continue to see significant additional increases in temperature that are well above the global average values.

Key Concepts and Vocabulary

Albedo: Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface. Ice, especially with snow on top of it, has a high albedo: most sunlight hitting the surface bounces back towards space. Water is much more absorbent and less reflective. So, if there is a lot of water, more solar radiation is absorbed by the ocean than when ice dominates.

 

Arctic ice cap: Polar ice packs are large areas of pack ice formed from seawater in the Earth's polar regions, known as polar ice caps: the Arctic ice pack (or Arctic ice cap) of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean, fringing the Antarctic ice sheet. Polar packs significantly change their size during seasonal changes of the year. However, underlying this seasonal variation, there is an underlying trend of melting as part of a more general process of Arctic shrinkage.

Satellite imaging: Satellite imagery consists of photographs of Earth or other planets made by means of artificial satellites. Satellite images have many applications in meteorology, agriculture, geology, forestry, biodiversity conservation, regional planning, education, intelligence and warfare. Images can be in visible colors and in other spectra. All satellite images produced by NASA are published by Earth Observatory and are freely available to the public.

Background Information

An extremely cold environment, low levels of light, and enormous mass of snow and ice characterize the Arctic region. This vast ecosystem is home to many diverse habitats and species, on the land and in the ocean, that depend on a constant amount of ice each season to survive. Arctic ice also acts as a very large mirror and heat sink for the Earth. Ice has a much greater ability to reflect short-wave radiation (albedo) reaching the Earth’s surface than water.  The different abilities of ice and water to reflect radiation translates to their different albedo values,   ~ 0-0.3 for water and 0.5-0.7 for ice (Figure 1). The Earth’s average albedo is approximately 0.3 (or 30%). The high albedo make ice and snow very important in keeping the Earth cool: they reflect much of the incoming solar radiation that is hits the Arctic region.

The size of the polar ice cap varies between seasons, with its greatest extent occurring in March and its smallest areal coverage in September. Scientists have been measuring the extent of the polar ice cap with NASA satellites (Fig. 2).  The pictures of the Earth from remote sensing instruments on such satellites enable scientists to evaluate the area of the Arctic region covered by ice and its thickness. According to these scientific measurements, Arctic sea ice has declined dramatically over at least the past thirty years, with the most extreme decline seen in the late summer melt season. In the summer months (July, Aug, Sept), the long term average (1900-1950) ice extent of the polar region was roughly 11 million km2. In the summer of 2007, the area dropped to a recent historic low of 5.5 million km2 (Fig. 3). 

This decline of ice coverage is important for the earth’s physical and ecosystem health. The ice cap is an important habitat and a major decrease in the ice area could cause extinction of many species. Reduced ice coverage also reduces the area of the earth that is reflecting solar radiation. As the increased area of water in the ocean surrounding the polar ice cap absorbs more solar radiation and warms, it causes the remaining ice to melt faster. This process is referred to as a positive feedback; where the outcome of a system feeds back to the system to further enhance its original outcome. 

Resources for Additional Background Learning

National Snow and Ice Data Center, University of Colorado, Boulder:  http://nsidc.org/pubs/education_resources/ 

Sea ice data and access to pictures: http://nsidc.org/data/seaice/index.html

Animations of Arctic ice extent or concentration: http://nsidc.org/sotc/sea_ice_animation.html

(tool to create your own animations - http://nsidc.org/data/seaice_index/archives/image_select.html)

Tour of the Crypsphere video: (http://svs.gsfc.nasa.gov/vis/a000000/a003100/a003181/index.html#media  , also at http://www.youtube.com/watch?v=PjAXoETeVIc for full screen access)

 

 

The Cryosphere Today - http://arctic.atmos.uiuc.edu/cryosphere/

Comparing Ice - Provides the ability to compare pictures of ice area from 1979 to present

National Geographic - 

"Ice Paradise: The rich life of Svalbard, Norway’s Arctic archipelago, faces a creeping thaw.”

Feature Article - http://ngm.nationalgeographic.com/2009/04/svalbard/barcott-text

Photo gallery - http://ngm.nationalgeographic.com/2009/04/svalbard/nicklen-photography 

Vanishing sea ice interactive map: http://ngm.nationalgeographic.com/2007/06/vanishing-sea-ice/sea-ice-interactive 

U.S. EPA Climate Change Summaries - http://epa.gov/climatechange/effects/polarregions.html 

Arctic Climate Impact Assessmenthttp://www.acia.uaf.edu/ 

Journal Paper: Arctic sea ice decline: Faster than forecast

http://www.smithpa.demon.co.uk/GRL%20Arctic%20Ice.pdf

A 5 page paper that is an in depth analysis of declining Arctic ice in September.

Instructional Strategies

General Approach

The goal of this activity is to use real data to explore and understand Arctic temperature and ice trends. This is done by looking at websites, viewing images, manipulating raw data, and using climate models to predict changes. The activity is broken into three parts:

  1. Reviewing pictures of the Arctic polar ice cap and estimating the extent of ice coverage.
  2. Reviewing data compiled in an MS Excel file that include information on the general changing trends in the surface air temperature and ice extent.
  3. Predicting future changes in surface air temperature with a Global Climate Model and inferring how sea ice might continue to change.

The activity requires students to work at a computer.  Pairs of students are suggested.

Implementation

Anticipatory Set: Set the stage for this activity with brainstorm or pre-class reading to define what the students know about Arctic sea ice losses and the impact of these changes on habitat and further climate change.  Some basic materials that could be used for introducing the importance of sea ice include:

"Ice Paradise: The rich life of Svalbard, Norway’s Arctic archipelago, faces a creeping thaw.”  http://ngm.nationalgeographic.com/2009/04/svalbard/barcott-text

Vanishing sea ice interactive map:  http://ngm.nationalgeographic.com/2007/06/vanishing-sea-ice/sea-ice-interactive 

Tour of the Cryosphere video: (http://learners.gsfc.nasa.gov/mediaviewer/Cryosphere/ also at http://www.youtube.com/watch?v=PjAXoETeVIc for full screen access)

Help students develop an understanding of the very important consequences of sea ice loss:

  • Reduced albedo that could further exacerbate the warming of ocean waters and climate change, a positive feed-back loop.
  • Habitatloss(polar bears and more)
  • Sea level rise

Procedure

  1. Review pictures of the Arctic polar ice cap and estimating the extent of ice coverage. Students access internet information about the extent of sea ice change in the Arctic Ocean to draw conclusions about 
  2. Review data compiled in an MS Excel file that include information on the general changing trends in the surface air temperature and ice extent. Students plot time series data and use linear regressions for a few locations around the ~80° north latitude to quantify the changes in temperature and sea ice extent and rates of these changes. 
  3. Predict future changes in surface air temperature with a Global Climate Change Model and infer how sea ice might continue to change. Students access an IPCC web site that provides results of many GCMs that have been run for standard future scenarios.  The students consider how much more the temperature is expected to change throughout this century and infer from their earlier analysis how the areal extent of Arctic sea ice will continue to change.

Closure Students can compare their findings, especially if different sets of students analyze March and September.  The key findings that should be reiterated include:

  • The temperature in the Arctic has already increased more than the global increase.  Predictions suggest that the temperature will continue to rise several degrees Celsius over the next decades.
  • Arctic Ocean sea ice has diminished substantially in area in September when it is at its minimum extent.  The net result is the opening of passageways through the Arctic Ocean and loss of land-ice connections that are critical for habitat, especially for polar bears.
  • Changes in sea ice area are correlated in time and space to ocean and land temperature changes.  The greatest changes are north of western Siberia and Alaska.
  • Reduced sea ice area means that the ocean temperatures will rise even faster as sunlight is absorbed by the water rather than reflected by the ice.
  • (optional) When sea ice melts it does not directly contribute to an increase in the mean ocean levels since the volume of ice is already displacing water.  However, as ice melts from the ice cap on Greenland, this land-based ice will contribute to seal level increases.

Learning Concepts

This data investigation is intended for an earth or environmental science class, although it could be done in combination with a geography unit as it incorporates several countries and continents in the Arctic region. Several mathematics concepts are included in this module that could be integrated with basic math class as well.

Science Standards

The following New York State and National Science Education Standards are supported by this chapter: (coming soon)

Assessment

The student worksheet can be collected and graded for assessment.

Other Resources

MS Excel file with regional temperatures and ice area

Student Worksheet

Powerpoint file that could be used to supplement introductory or closing discussion for this unit.

Case Study: How is Arctic Ocean Sea Ice Changing?

Arcitic Ocean temperatures have increased over the years and the extent of sea ice has decreased.  The example below looks at one region north of Alaska to understand the extent of these changes.

Part 1: Information from Cryosphere Today:

As shown in the figure below, the areal extent of Arctic Ocean Ice has changed dramatically over the past 30 years.  These images show the extent of ice in September, which is the annual minimum.  As shown in the circles, ice loss has been most dramatic in the region north of Alaska and Siberia.  Ice loss in northern Canada has resulted in the opening of a navigable passageway.

 

Scientific analysis of the extreme ice loss in 2007 shows that the air temperature north of the Alaska/western Siberia region and in the islands of northern Canada to be well above normal (+4°C) in the summer months, and even further above normal (+6-12°C) in September and October.  These extremely high temperatures contributed

 

Part 2: Quantitative assessment of changes

Analysis from the MS Excel workbook included an assessment of changing ocean air temperatures in September from -154° to +154° longitudes at 80° latitude.  It was expected that a significant increase in temperatures in this region would be correlated to the changing sea ice extent since that is one of the areas close to the most substantial losses in September sea ice.

As shown in the graph below, the ice extent decreased by approximately 2 million km2 over the period for which we have data (1994-2008).  The rate of loss was determined from the linear regression ~ -0.15 million km2 lost per year.

The ocean air temperatures increased substantially over this same period ~10°C.  This is a huge amount given an overall surface air temperature increase over the last century of less than 1°C.  The ocean temperatures are changing at ~0.45°C per year.

 

Another way to look at these trends is to plot the ice area as the dependent variable and the ocean air temperature as the independent variable:

 

The graph shows that the Arctic region loses ~0.22 million km2 ice for every degree (°C) rise in ocean air temperature in the region -154° to +154° longitude at 80° latitude.

Part 3: Predicted future temperature changes

The IPCC DDC maps tool was used to look at projections of 20 year temperature anomalies for the region 78-82° latitude and -154 - +154° longitude.  The temperature anomalies are relative to the 20th century average.  IPCC DDC selections included:

  • 4th assessment report
  • Scenario SR A2
  • 20 year average temperature anomalies (September 2080-2099)
  • NASA's GISS-ER model

The results show that the September average air temperature at the end of this century is expected to be ~5°C higher than the 20th century average.  This is much higher than the 2°C goal set in the Copenhagen accord.  The continue rise in temperatures are expected to bring further loss in the September sea ice. Based on the graph above, a 5°C increase should result in an additional loss of 1.1 million km2 (0.22 x 5 = 1.1) of sea ice by the end of the century.  Actual predictions, however, suggest that the rate of sea ice loss will be even faster.  The change in albedo and positive feedback loop that that contributes to ocean warming is not adequately captured in our linear regression and extrapolation analysis.

 

Step-by-Step

Part 1 - What is the extent of ice coverage in the Arctic sea?

Part 2 - How has the Arctic polar ice cap changed over the past several years?

Part 3 - How might sea ice continue to change?

Part 1 - What is the extent of ice coverage in the Arctic sea?

Data satellite images of the polar ice cap are available through the National Snow and Ice Data Center and the Cryosphere Today web sites.  Explore these sites to address the following questions:

  1. Over the very long term (centuries) how has the extent (area) of Arctic ice changed? (see Cryosphere site)
  2. In what regions of the Arctic is the ice cap changing the most (look at September).   
  3. Where does the data on polar ice cap extent and thickness come from? 
  4. How will these changes in sea ice coverage affect Arctic wildlife?  What geographic regions should we be most concerned about?

Use the images included on the student worksheet and graph paper provided to estimate the minimum extent of ice coverage in September of two different years.  Note – as a reference point, the area of Greenland is 2,166,000 km2.

  1. What ice extent areas did you determine and how do your estimates compare with published values? 
  2. What percentage reduction in ice coverage do your estimates show (express your results as % reduction per decade)?

Part 2 - How has the Arctic polar ice cap changed over the past several years?

2.1 Exploring Temperature Trends

An MS Excel data file has been created to show how temperature and ice extent have changed over the past decades.  The data were collected for a latitude of 80° north to represent the approximate circumference of the region. A globe, world map or Google Earth are a useful tool to identify the location of each temperature data set. Use the data in the MS Excel file to address the following questions: 

  • How has land surface temperature changed in the Arctic since 1930? (provide an absolute measure (°C from 1960s to the present), and a rate of change for the early time data and the later time data)
  • How has ocean temperature changed since 1994?
  • How do the ocean temperatures versus land temperatures compare?
  • Are there any differences in the rates of temperature change in March (when the sea ice is at its maximum extent) versus September (sea ice minimum extent)?

Suggestions - some student groups can look at March data and others at the September data set. If the instructor choses to reduce the complexity of this exercise, it is better to only look at the September data; that is where the most substantial changes have occurred.  The excel spreadsheet can also be simplified with fewer longitudinal locations.)

Approach:

Choose several longitude locations (columns) from the temperature spreadsheet pages.  Plot the data as a function of time and identify any trends (increasing or decreasing).  The slope of a linear regression equation can be used to define the rate of change in the temperature (°C/year). 

2.2 Exploring Ice Trends

The MS excel spreadsheet used above also includes information on the extent of the ice coverage.  Use these files as well as information on scientific web sites to address the following questions: 

  • How has the area of ice changed from early 1900s to the present day? 
  • Are the recent short-term changes in ice extent the same or different than long-term trends (sea ice loss per decade)?  Explain any differences that you note.
  • Can connections be made between the temperature data and ice data? 
    • What are they?
    • Are the greatest changes in air or ocean temperatures correlated to the regions where the greatest losses in sea ice have occurred? Where are these regions?  Do they have any particular significance from a habitat or transportation perspective?

Approach:

(If part 1 not done) Open The Cryosphere Today and begin exploring trends in ice over the past 100 years. Start by viewing a seasonal and annual ice trend graph on the website. This is an excellent visual of how ice extent was stable in the early 1900s and begins to decline after 1950. In addition, there are good images and movies on the website that show ice trends. The images can be used to compare ice area side by side for two different dates from 1980 to the present. 

The movies show how ice breaks up and reforms over a one-year timeframe. These movies are available on the website. All require either Quicktime or Windows Media Player to view. This site is meant to give an overview of the historic and annual trends that Arctic sea ice undergoes. 

After viewing The Cryosphere Today, the MS Excel data file should be opened to the Ice Data spreadsheet.  Plot the ice extent versus time.  Use a linear regression to determine the rate of loss of ice (million km2 lost/year) for March and/or September for the decades - 1980s and 2000s. 

Compare trends(plots created above) in temperature changes and ice changes.  Comment on the relative rates of change.

Significant analysis has been completed to understand why the ice coverage in 2007 was so low.  The following images illustrate the temperature anomaly (difference between actual temperature and long term average temperature for the month over past decades) for the summer months of 2007.

Part 3 - How might sea ice continue to change?

Global climate models can be used to predict changes in air and ocean temperatures and other indicators of climate change.  The simulation results from several different climate models are available in the IPCC DDC resource (see also the tutorial for using this web site). 

Explore the results of climate model simulations to address the following questions:

  • How is the temperature predicted to change in the Arctic?
  • How is this change different among the different scenarios?
  • What can you infer about how the Arctic polarice cap might change as a result of the predicted temperature changes?
  • Do you think that these changes are important in terms of ecosystem health or how the earth functions? Why?

Approach: Using the results of simulations included in the IPCC DDC web resources, surface air temperatures for 80 degrees latitude can be predicted up to 2100 for most models and scenarios. This can be shown in a longitude series for a single month in the selected year. The user has the option to choose results from a particular model (data set) and for a particular scenario considering how our future world functions and its associated GHG emissions. (Use the 4th assessment report models, scenario SRA2 as a worst case for our future climate and SRB1 as a best case.  Choose the NASA model “GISS-ER” and 20 year anomalies to see how much the temperature in this region will change by 2080-2099.  Consider changes in both March and September.

Tools and Data

Tools

Microsoft Excel: A spreadsheet application is needed to analyze the data. Microsoft Excel is used in this chapter and is available as part of Microsoft Office.

Tool Builder

Microsoft Corporation - www.microsoft.com

Tool Cost

Excel is part of the suite of Microsoft Office software. Students and educators may be able to purchase this software at a reduced cost. The Student and Home Edition is sufficient for use in this module.

Data Set

Data Set 1

The surface air temperature data included in the Excel spreadsheet was acquired from the University of Delaware, Department of Geography in the Climate Workshop folder or (http://climate.geog.udel.edu/~climate/index.shtml) and is available in its original format from 1930 to 2004 by year.  Scientists at this site collected weather station data from several resources and interpolated these data to provide estimates of monthly average temperatures throughout the Arctic region.  For an explanation of the science behind these data, see http://climate.geog.udel.edu/~climate/html_pages/Arctic4_files/README.arctic.t_ts4.html

Data Set 2

Data for the air temperature over the ocean that are included in the Excel spreadsheet were acquired from My NASA Data (http://mynasadata.larc.nasa.gov/data.html) in a ASCII file format. This data access web site presents weekly average sea temperatures for latitudes from 80° north to 80° south.  The data were collected from a NOAA satellite with the Advanced Very High Resolution Radiometer (AVHHR), which is the primary sensor on NOAA polar orbiting satellites. It detects cloud cover and surface temperatures of cloud layers, land and water.

Data Set 3

Ice area data included in the Excel spreadsheet was downloaded from National Snow and Ice Data Center at this link: http://nsidc.org/data/g02135.html and is also available in the Climate Workshop folder. This data set was originally generated from brightness temperature data obtained with a NASA satellite. The satellite carried an instrument – the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) that uses a passive microwave approach to provide a consistent time series of sea ice concentrations (the fraction, or percentage, of ocean area covered by sea ice). For further details, see http://nsidc.org/data/nsidc-0051.html .