# Teaching Notes

In this Section

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.

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

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

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.