In polar regions, areas of sea ice -- ice atop ocean waters -- not only supports entire ecosystems, it affects Earth’s climate by reflecting sunlight back into space rather than absorbing it. Since polar regions are often cloud covered, scientists use microwave sensors onboard satellites (such as JPSS’s ATMS) to “see through” the clouds and make measurements of sea ice. The term “ice concentration” refers to the percent of ice coverage in the sensor’s pixel area, not the thickness of the ice. This image plots the maximum extent of sea ice concentration, which usually occurs in April each year.