WHY IS SEA ICE IMPORTANT?

Like the oceans, which moderate Earth's climate by absorbing and storing heat efficiently, polar regions also play a key role in regulating Earth's temperature. The Arctic is the region on Earth where the greatest changes resulting from global warming are predicted. If Arctic sea ice is thinning over the next decades, as sparse observations are indicating, this could change the circulation pattern of the north Atlantic Ocean, thus changing the supply of heat to western Europe. The sources for the observed global sea level rise are not well identified. Are the Greenland and Antarctic ice sheets melting and therefore contributing to worldwide sea level rise? The question cannot be answered today.

The oceans absorb heat readily and store heat better than land, which is why climates are more temperate in coastal regions. When the polar ocean water freezes into ice, it no longer absorbs heat but reflects it instead. As a matter of fact, ice reflects both heat and light. The ice may not be absorbing any new heat from the Sun but it actually inhibits heat flux from the ocean into the atmosphere. Think of sea ice as providing a layer of insulation between the ocean underneath and the atmosphere above.

The amount of ice cover in the polar regions contributes significantly to the overall heat exchange for the planet. The greater the area of ice cover, the less heat transfer there is. Polar oceanographers study the extent of the ice edge in an effort to better understand the role this plays. The key measurements for climate include ice thickness, the motion of the ice, and summer melting.

Polynyas, which are located within the ice edge, provide oases of heat exchange in the frozen desert. Since they are often "ice factories," they are continually releasing heat to the freezing process. And, since they remain open to the atmosphere, heat fluctuations may take place, providing an outlet for some of the ocean's heat that would otherwise be kept insulated by the ice cover. Also, during ice formation salt is released, which sinks to deeper levels of the oceans forming key layers of the world's oceans.

ABOUT THE LECTURE

The lecture is represented on the screen with three independent frames. The frame across the top right contains the title, buttons you can use to move between the two parts, and links to the different sections of each part. The frame below it on the right displays the text of the selected section, and buttons at the bottom also allow you to move between sections. The vertical frame on the left side presents thumbnails of all graphical figures from the selected part. Each thumbnail links to a larger image for viewing and printing. All citations for graphics and text are found in each part's References section.

Part 1: Polar Sea Ice Processes

Part 2: Determining Sea Ice Concentration From Passive Microwave (SSM/I) Observations