Shop Windows to the Universe

The Winter 2010 issue of The Earth Scientist includes a variety of educational resources, ranging from astronomy to glaciers. Check out the other publications and classroom materials in our online store.
This sea ice in the Beaufort Sea is light in color compared with the dark ocean water. The sea ice reflects most of the sunlight that hits it. The ocean water absorbs most of the sunlight that hits it.

Ice-Albedo Feedback: How Melting Ice Causes More Ice to Melt

Arctic sea ice is covered with snow all winter. Bright white, the snow-covered ice has a high albedo so it absorbs very little of the solar energy that gets to it. And during the Arctic winter, very little solar energy gets to it anyway. The Sun stays low on the horizon, days are short, and above the Arctic Circle there is at least one day of winter when the Sun does not make an appearance at all.

However, as summer approaches, the Sun climbs higher in the sky each day, and temperatures warm. The snow on the surface melts and the bare sea ice is exposed. Summer is a warmer time than winter, but it becomes even warmer as the ice changes and melts. The ice is darker in color than the snow. Melt ponds and cracks called leads forms in the ice, which are also darker in color. And where the ice has melted, dark ocean water is exposed. These changes decrease the albedo. With a lower albedo more solar energy is absorbed and less is reflected. This causes more ice to melt, which in turn lowers the albedo, causes more energy to be absorbed and more warming to occur.

Because Earth’s temperature is climbing as more greenhouse gases are released into the atmosphere, the snow on top of the ice melts earlier in the spring and temperatures drop to the chilly levels at which sea ice can form again little later in the fall. There is more time during the summer for the compounding cycle of melting ice, lowering albedo, trapping of more solar energy, and more ice to melt.

This process of a little warming causing more warming is called the ice-albedo feedback and it is one reason that the Arctic is very sensitive to changes in temperature. The ice-albedo feedback can turn a small climate change into a big climate change. The sea ice is melting rapidly in the Arctic Ocean. In about the past three decades the amount of ice covering the Arctic Ocean has dropped about a million square kilometers (about the size of Alaska). According to climate models that pace of ice melt will continue to quicken so much that that there may be no more summer sea ice within the next few decades.

There have been times in Earth history when ice-albedo feedback has worked in the other direction. That is, climate cooled and more ice formed, albedo increased, which decreased the amount of sunlight absorbed, and climate became even cooler, which caused more ice to form. For example, at the end of the Proterozoic Era more than 800 million years ago, Earth went through a period where temperatures plummeted worldwide. This time is known as “Snowball Earth” because there is geologic evidence that ice formed worldwide, even near the equator and at low altitudes. Scientists have used computer models to test what could have caused this extraordinary cooling. They have found that a runaway ice-albedo feedback could have been the cause of the extreme and rapid cooling that caused “Snowball Earth”.
Last modified July 18, 2007 by Lisa Gardiner.

Shop Windows to the Universe Science Store!

The Winter 2009 issue of The Earth Scientist, focuses on Earth System science, including articles on student inquiry, differentiated instruction, geomorphic concepts, the rock cycle, and much more!

Windows to the Universe Community



You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Sea Ice in the Arctic and Antarctic

Sea ice is frozen seawater. It can be several meters thick and it moves over time. Although the salts in the seawater do not freeze, pockets of concentrated salty water become trapped in the sea ice when...more


This picture shows a part of the Earth surface as seen from the International Space Station high above the Earth. A perspective like this reminds us that there are lots of different things that cover the...more

Effects of Climate Change Today

The world's surface air temperature increased an average of 0.6° Celsius (1.1°F) during the last century according to the Intergovernmental Panel on Climate Change (IPCC). This may not sound like very...more

Earth's Greenhouse Gases

Less than 1% of the gases in Earth's atmosphere are called greenhouse gases. Even though they are not very abundant, these greenhouse gases have a major effect. Carbon dioxide (CO2), water vapor (H2O),...more

What if there were no Antarctica?

I'm in Antarctica right now, and wondering what this place might look like in a hundred or more years. What would Earth be like if there were no Antarctica? Human induced climate change has the potential...more

Black Carbon

Little particles in the atmosphere called aerosols may be small but they have the ability to change climate. These tiny particles are a natural part of the atmosphere, coming from erupting volcanoes, sea...more

Content for Climate Change Education Courses

Looking for online content that can be used for a climate change education course or module? Pages linked below can be used to support an introductory climate change education for either a unit or a full...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA