Other scientists study ice cores to understand the history of climate They drill cores deep into ice sheets or glaciers and analyze gases trapped in bubbles within the ice These gases provide glimpses of the composition of past atmospheres They allow scientists to determine atmospheric temperature at those times Scientists have used ice cores to build a picture of Earth’s climate for the past 800,000 years An understanding of past climates can help predict future climates including rates of ice melt SATELLITES PHOTOGRAPH ICE MELT Surface ice on Greenland’s ice sheet is the top of the ice only The ice sheet is only a few meters thick at its edges but toward the center it can be 10,500 feet 3,200 m or almost 2 miles thick 4 On average melt occurs over approximately one-half of the ice sheet’s surface during the summer But in 2012 melt occurred over nearly all of the surface The melt progressed from approximately 40 percent on July 8 to 97 percent by July 12 5 Surface meltwater quickly refreezes over most of the ice sheet But near the coast much of it drains into the ocean The 2012 change was documented by three satellites measuring different ice properties and passing over Greenland at different times Lora Koenig a glaciologist who helped analyze the data says such extreme melts happen approximately every 150 years The last one was in 1889 But if they continue to happen as scientists expect it will be worrisome Koenig says 6 Scientists also make on-the-spot measurements of physical characteristics including temperature rates of glacier retreat and rates of sea ice melt Their tools range from sticks jammed in the ice to measure height to the latest scientific instruments To measure changes in land ice they travel over ice sheets often in bitter cold and high winds To measure sea ice they conduct cruises on research vessels dodging ice floes One reason for on-the-spot investigations is simply that they bring home the reality of climate change and ice melt much more clearly than photographs or pages of numbers Also those firsthand observations and measurements can validate the data from satellite images 8
MELTING SEA ICE Scientists at the National Snow and Ice Data Center in Boulder Colorado have been collecting precise measurements of the extent of melting Arctic sea ice since 1978 Nearly 40 years of data show a clear rapid melting trend Ice amounts are always at their minimum during the month of September at the end of summer melting Since measurements began total September ice coverage has decreased rapidly In the 1980s the Arctic contained approximately 773,200 square miles 2 million sq km of old ice or ice that is at least five years old By 2010 there were only 22,000 square miles 57,000 sq km of old ice a decrease of more than 97 percent 7 Researchers are trying to figure out why Arctic ice is melting so rapidly A 2015 international research expedition led by Harald Steen of the Norwegian Polar Institute surveyed a region around the North Pole on the RV Research Vessel Lance The group spent an entire season on the ship from January through the early summer ice breakup They seldom used engines instead drifting through ice floes and worked through six weeks of the 24-hour darkness of polar winter They explored nearby ice floes on foot skis and snowmobiles 9 DRONES MEASURE SEA ICE Christopher Zappa uses unmanned airborne vehicles or drones to study Arctic ice melt Drones get closer to the action than satellites and allow him to study much wider areas than when working from a research ship With drones he says we can study melting and other processes as they’re happening on a very fine scale 8 Zappa is an oceanographer at Columbia University’s Lamont-Doherty Earth Observatory He and his colleagues launch drones from the Svalbard Archipelago a group of islands between Norway and the North Pole Each eight-foot 2 4 m drone carries up to 10 pounds 4 5 kg of scientific instruments They travel halfway to Greenland and back on each four-hour trip skimming the water surface to make close-up observations Different instrument packages measure variations in water and ice temperature the structure of disintegrating ice and ocean salinity or saltiness
RV Lance is one of many research ships that scientists use to study the extreme Arctic region and lowered buoys from the ship to measure water characteristics They braved harsh winds and temperatures as low as 40 degrees Fahrenheit 40 C to study the formation and breakup of younger thinner sea ice They also had some confrontations with polar bears and had to be towed by the Norwegian Coast Guard after getting stuck in the ice Yet such research voyages are essential to understanding how and why All the climatic processes seem to be pushing rapidly toward a seasonally ice-free Arctic Ocean 9 Dr Julienne Stroeve National Snow and Ice Data Center 10
ice is melting now They are also essential to understanding the future of Arctic ice CALVING GLACIERS It is difficult to catch the process of calving as it happens But sometimes good data and a good movie result from a combination of luck preparedness and perseverance Just ask the film crew of the movie Chasing Ice which centers on nature photographer James Balog Balog’s goal was to document the melting of Arctic ice due to climate change He began his crusade to document climate change in 2005 when National Geographic sent him on assignment to the Arctic Balog was originally a climate-change skeptic He thought statements about climate change were based only on computer models with no concrete measurements involved But that first Arctic trip convinced him of the reality of climate change He created the Extreme Ice Survey an expedition that would keep him and a small group of intrepid explorers visiting the Arctic for years They assembled a series of time-lapse cameras in the savage Arctic environment and kept them running They captured years of ice footage and compressed it into seconds documenting the movement and rapid disappearance of Arctic ice 11 OPERATION ICEBRIDGE The National Aeronautics and Space Administration NASA project Operation IceBridge has made airborne surveys of Arctic and Antarctic ice since 2009 IceBridge gives scientists a multiyear three-dimensional view of ice sheets ice shelves and sea ice It uses many instruments to show the rapid changes in polar ice Arctic flights have gathered data on changing elevations and the internal structure of the Greenland ice sheet They found a 460-mile 740 km canyon beneath a mile 1 6 km of ice and a vast area of liquid water under the snow in southern Greenland 10 IceBridge data helps scientists better predict the summer melt season and better understand yearly variations in ice thickness
