How do we know that Arctic Sea Ice is slowly melting? Key Concept The expanse of floating Arctic Ice is seasonal. For the last 30 years we have measured the extent of the sea ice from satellite photographs taken in late August or early September. From year to year the ice level fluctuates, sometime it increases and sometimes it decreases. The key to interpreting the data set is to look at many points over a long period of time to determine the trend.
What You Should Know
Sea ice is frozen ocean water.
The white color of the sea ice reflects 80% of the sunlight that strikes it.
Liquid, unfrozen ocean absorbs 90% of the striking sunlight.
The sea ice helps keep the polar regions cool and moderates weather globally.
Draw a best-fit line through the data points on your graph. You can do this by using a ruler. Draw a straight line at the point where approximately half of the points are above the line and half are below the line.
Answer the conclusion questions.
What kind of graph will you use to display the data? Why?
How should you orient your graph paper? (Draw a sketch here.)