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Step-by-Step

In this Section

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.