Arctic sea ice goes through swings every year. Ice typically grows from October to February, and then slowly melts during the spring and summer months. During the end of the winter months, the greatest development of ice is called the annual maximum. Then, during the end of summer around September, the decline of ice is at its annual minimum. NASA created a video showing the decline of the ice from its near-maximum state (in early spring 2011) to the near-minimum state (in September 2011) using the AMSR-E instrument on NASA’s Aqua satellite.
When it comes to climate change, scientists are worried about the decline in Arctic sea ice. As the white, reflective ice disappears, darker ocean waters appear. Snow and ice have a high albedo, meaning that a lot of sunlight reflects away from the surface. Ocean waters have a lower albedo, which means more sunlight can be absorbed into the water due to less reflectivity. If we see more ocean and less ice, more melting can occur. In the image below, Arctic sea ice is smaller than ever before. Ice extent is the lowest it has been for 2011, even at the maximum in March – that is, the maximum for 2011 is smaller than previous maximums.
According to NOAA’s National Climatic Data Center (NCDC), August 2011 was the 15th consecutive August and 123rd consecutive month that saw below-average Arctic sea ice extent. (The average period is from 1979 to 2000.) During the month of August 2011, the average Arctic sea ice extent was 28 percent below the long-term average, ranking as the second smallest August extent since satellite records began in 1979. Arctic sea ice volume reached a record daily low on August 31, 2011, of 1,026 cubic miles (4,275 cubic kilometers). The previous record daily low was held back in September 15, 2010, with 1,062 cubic miles (4,428 cubic kilometers).
The NCDC also includes that the difference between the August 2011 extent and the long-term monthly average was around 830,000 square miles (2.15 million square kilometers), which is roughly the size of Greenland.
Bottom line: Arctic sea ice is shrinking. NASA’s video shows the extent of the melting of ice from early spring 2011 into September 2011. The minimum is the lowest ever measured.
Matt Daniel is weekend Meteorologist for 13WMAZ (CBS) in Macon, Georgia, and founder of the blog Athens GA Weather. He's a self-described "big weather and music geek" and has produced weather content for CNN, MSN Weather and EarthSky. He has a passion for helping to keep people safe when severe weather strikes and says if you don't have a NOAA Weather Radio ... you should get one.