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VICE News is closely tracking global environmental change. Check out the Tipping Point blog here.No, it's not an ultrasound of someone's internal organs. It's sea ice in the Arctic Ocean melting because of climate change.Scientists have been using satellites to monitor the yearly fluctuation in the extent of sea ice in the Arctic since the 1970s. But the amount of area covered by sea ice is far from the whole story. Satellites can also be used to measure the age of the ice — and scientists are worried about the data their instruments are beaming back to Earth.
Due to warming ocean temperatures over the past several decades, a greater amount of perennial ice, that is: sea ice that is more than a year old, is melting."We've come to an era where the older ice is getting to be less observed and the coverage of the ice pack now is a lot more first-year ice and second-year ice," Mark Tschudi, a research associate at the University of Colorado-Boulder told VICE News. "In general, older ice tends to be thicker ice, so the fact that the pack has transformed into a pack of younger ice means it's more susceptible to melt out in the summer."The National Oceanic and Atmospheric Administration used Tschudi's data to construct the animation of sea ice cover in the Arctic.Decades ago, the majority of the Arctic's winter ice pack was made up of thick, perennial ice. Today, very old ice is extremely rare. This animation tracks the relative amount of ice of different ages from 1987 through early November 2014. (Video by Climate.gov, data by Mark Tschudi)Sea ice is highly reflective, sending about 80 percent of the sunlight that hits its surface back into space. But when it melts, incoming sunlight hits the ocean's surface, which, because it is darker than ice, absorbs 90 percent of the sunlight. This contributes to warming ocean temperatures, which, in turn, causes more ice to melt.Using data collected by buoys in the Arctic Ocean and a satellite-mounted instrument known as the Special Sensor Microwave Imager, Tschudi tracked the variation in the age of sea ice age from 1985 through 2014. In March 2014, ice that had made it through four or more seasons comprised 10.1 percent of the pack, an improvement over 2013's 7.2 percent, but a significant drop from the average of 26 percent in the 1980s.
"The trend is pretty overwhelming towards having a younger pack, compared to looking back to the 1980s when we first start looking at this," Tschudi told VICE News.The long term trend in the Arctic points to a decrease in ice coverage, particularly from old ice, meaning the pack is becoming younger and thinner and thus more likely to melt completely in the summer.Arctic sea ice usually reaches its greatest extent in March, then begins to retreat as temperatures warm in Spring and Summer. Historically summer sea ice extent reaches its minimum in September.Summer sea ice extent reached an all-time low in 2012, covering only 1.3 million square miles, compared to the 1979-2000 average minimum of 2.57 million square miles — a 49 percent decrease.The six lowest seasonal minimums in the satellite record have all occurred since 2007.Predictions on when the Arctic may see an ice-free summer vary, with one NOAA scientist saying it is "very likely" by mid-century. In November, an English physicist using data from submarines beneath the ice said an ice-free Arctic may come by 2020.2014 was the hottest year ever recorded. Read more here.Follow Laura Dattaro on Twitter: @ldattaroImage via Flickr