text: Warm Atlantic waters wage a new assault on Arctic ice from below 
   
   A new enemy is undermining ice floating on the Arctic Ocean: heat from below. 
   
   Sensors that have plumbed the depths of Arctic seas since 2002 have found warm currents creeping up from the Atlantic Ocean and helping drive the dramatic retreat of sea ice there over the last decade. A new study shows this “Atlantification” of the Arctic Ocean as a new, powerful driver of melting, alongside losses due to rising air temperatures. 
   
   The paper shows “a massive shift” in the behavior of the Arctic Ocean over a short time, says Finlo Cottier, a physical oceanographer with the Scottish Association for Marine Science in Oban who was not part of the study team. “Here we’re seeing an ocean basin changing on a generational timescale—or less,” he adds. 
   
   Deep below the Arctic sits a ridge that splits the ocean roughly in half: The Amerasian basin sits on the North American side, whereas the Eurasian basin lies north of Europe and most of Asia. Both basins are losing ice fast. Across the entirety of the Arctic Ocean, it’s disappearing at an eye-popping rate of 13% per decade since satellite data was available. It has also thinned by 1.7 meters since the 1970s. 
   
   Warm Atlantic waters, delivered by an offshoot of the Gulf Stream, have long been known to prevent ice formation north of Scandinavia, on the western side of the Eurasian basin. Satellite data show that, in general, sea ice is much more prevalent in the eastern side of the basin, north of Siberia. But over the last decade, ice has also begun to disappear here, too. It used to persist through the sunny summers, allowing several years of ice growth to accumulate. Now, the ice melts in summer, causing the total time without floating ice in the region to jump from less than 1 month per year to more than three. 
   
   To understand this new trend, scientists in 2002 began installing sensors on lines tethered to the floor of the Eurasian basin, called moorings. The team relied on a total of nine moorings, augmented with satellite data and sensors bolted below drifting sea ice and along ice frozen to the shore. When they retrieved data from the moorings in 2015, they found that the ocean had experienced a dramatic change over the previous decade, especially during the winter. 
   
   Between Norway and Greenland in the western Eurasian basin, Atlantic currents flow into the Arctic at a depth of 200 to 250 meters, about 4°C warmer than the surface water. In winter, cold air cools surface waters until they fall and mix with the warm waters below. That creates an overall warmer, well-mixed ocean over the top 250 meters, and one with little sea ice. 
   
   On the eastern side of the basin, however, the warm Atlantic waters were kept at bay—until recently. The currents lurked at a depth of about 150 meters, but they didn’t mix much with surface layers, because of a barrier called the cold halocline layer (CHL)—a boundary between salty deep waters and fresher water on top. Summer ice, as it forms, rejects salt, leading to the creation of dense, salty waters just below the ice. Those waters are heavier, and as they fall they create a highly stratified ocean. “Previously this monster, Atlantic warm water, was well covered from the surface” by the CHL, says Igor Polyakov, a physical oceanographer at the University of Alaska in Fairbanks, who led the study. “The new data show this layer has disappeared in winter.” 
   
   The result, he says, is an increased “Atlantification” of the Arctic, where the eastern side of the Eurasian basin is becoming more like the western side, the team reports today in Science . The top of the Atlantic water, according to one mooring, had risen from a depth of 140 meters in the winter of 2003–04 to a depth of 85 meters just a decade later. Without summer sea ice forming to establish the CHL, he says, the ocean mixes more—and less ice forms. 
   
   On the eastern side of the Eurasian basin, say Polyakov and his colleagues, air temperatures were the main culprit for ice melting in the 2000s. Now, however, they believe air temperatures and warm waters share the blame about equally. Polyakov says a positive feedback loop is underway, in which less summer sea ice will lead to warmer winter waters and even less summer ice in subsequent years. One unknown is how the addition of massive flows of freshwater from Siberian rivers, bolstered by thawing permafrost, could affect the system, says study co-author Eddy Carmack, an oceanographer with Fisheries and Oceans Canada in Sidney. That new freshwater could encourage more sea ice to form on the basin, unless winds wash the new water away. ||||| Thank you for your interest in spreading the word about Science. 
   
   NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address. ||||| Climate change is melting the sea ice so rapidly that parts of the Arctic ocean are beginning to take on characteristics of the Atlantic ocean. The change could affect everything from how freshwater is stored and delivered to how the ocean itself responds to increasing acidity, according to a study published in the journal Science on Thursday. 
   
   When healthy, the Arctic ocean exhibits a surprisingly resolute system of stratification — thick layers of ice that provide a natural barrier to nutrient mixing, one of the hallmarks of an ocean like the Atlantic. The Atlantic’s mixing process, by which it draws heat upward from the deeper ocean and circulates nutrients, means that the base of its food web is more prolific, resulting in more alkaline water. When it comes to how an ecosystem like this will function in the Arctic, however, we’re in uncharted waters — it is, after all, a region that traditionally doesn’t see much overturn. 
   
   “There is ongoing debate that heat release from a more open Arctic ocean will affect mid-latitude weather patterns,” co-author Eddy Carmack explains to Inverse over email. “More open water means that winds may more actively drive freshened surface waters, with regional consequences.” 
   
   The Arctic’s eastern Eurasian Basin has been basically ice-free for nearly six years. By comparing satellite estimates from 2013 to 2015 for the thickness of what ice does remain to previously published work, the researchers found that the region is rapidly exhibiting weakened stratification, with less sea ice and more vertical mixing — i.e., more like the Atlantic. 
   
   We know, of course, that sea ice has been melting. But this new data helps us better understand the role of the ocean beneath as the ice itself retreats and thins. The researchers found that both the ocean’s recycled heat (stored in the warmer summer months and then released in the winter) and its imported heat (pulled up from warmer subarctic seas to the south) play an increasingly large role in the sea ice’s decline. 
   
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   This isn’t the first time researchers have quantified the effects of global ocean warming using satellites, an increasingly handy tool in the battle against climate change. Carmack and his colleagues used satellite data to observe changes in the coverage and thickness of the sea ice, as well as the speeds and trajectories of its drift. They were also able to use satellites to determine the ice’s age — the length of time it spent in the Arctic before either melting off or being ultimately exported into the surrounding subarctic oceans. They combined that information with data gathered from local buoy systems to be able to make the comparison between the Arctic and the Atlantic, and begin to extrapolate exactly what kind of consequences we might be looking at. ||||| The Arctic is undergoing an astonishingly rapid transition as climate change overwhelms the region. 
   
   New research sheds light on the latest example of the changes afoot, showing that parts of the Arctic Ocean are becoming more like the Atlantic. Warm waters are streaming into the ocean north of Scandinavia and Russia, altering ocean productivity and chemistry. That’s making sea ice recede and kickstarting a feedback loop that could make summer ice a thing of the past. 
   
   “2015 was a really anomalous year when we had problems finding a suitable ice flow to launch our drifting buoys,”Igor Polyakov, an oceanographer at the University of Alaska who led the new study, said. “(There was) nothing like that in the past, and it became a motivation to our analysis: why was ice in 2015 so rotten? What drives this huge change?” 
   
   The findings, published in Science on Thursday, show that while warming air has a role to play, processes are playing out in the ocean itself that are fundamentally altering the region. 
   
   Those changes will have impacts on the people, plants and animals that call the Arctic home. They could also create more geopolitical tension as resources previously locked under ice become available and shipping lanes open up. 
   
   In the east Arctic Ocean, the shift is manifesting itself in changing the layers of the ocean. There’s a cap of cold, less salty water that covers the eastern portion of the Arctic Ocean. Underneath it sits a pool of warm, salty Atlantic water that until recently hasn’t been able to find a way to surface. That stratification of layers has kept ice relatively safe from its warm grip. 
   
   The ocean has become gradually less stratified since the 1970s. Using data from buoys and satellites, Polyakov and his colleagues have found a more marked shift over the past decade and a half. Since 2002, the difference in water temperatures between the layers has dropped by about 2°F. 
   
   In winter from 2013-2015, the cap separating the deep water and surface water disappeared completely in some locations, allowing the warm Atlantic waters to reach the surface and cut further into sea ice pack. At the same time, warm air has further reduced sea ice, which is allowing still more mixing of the ocean layers. 
   
   The result is a feedback loop that is essentially turning roughly a third of the eastern Arctic Ocean into something resembling the ice-free Atlantic Ocean. 
   
   “Rapid changes in the eastern Arctic Ocean, which allow more heat from the ocean interior to reach the bottom of sea ice, are making it more sensitive to climate changes,” Polyakov said. “This is a big step toward the Arctic with seasonal sea-ice cover.” 
   
   The changes are already apparent in the region, which has largely been ice-free during the summer since 2011. The sea ice winter maximum, which has set a record low for three years running, has been largely driven by a lack of ice in the eastern Arctic. 
   
   Polyakov said he’s seen the rapid changes in ice firsthand. When they first put buoys in the eastern Arctic in 2002, researchers had to reach the sites on heavy icebreakers. 
   
   “Now we can reach them using an ice class ship,” he said. Ice class ships are not necessarily as reinforced as icebreakers. 
   
   The sea ice changes are having profound impacts outside of researchers’ ability to access more remote sites. Other research published earlier this week in Science Advances shows that thinning sea ice is allowing phytoplankton to bloom across the region. 
   
   Phytoplankton are tiny plants, and like your average potted plant, they need sunlight to bloom. Sea ice has been thick enough to prevent that from happening until very recently. The new findings show that over the past decade, up to 30 percent of the Arctic has become primed for summer blooms. 
   
   “Both of our results show the Arctic becoming a very different place than it has been in the past,” Christopher Hovart, an oceanographer at Harvard who led the plankton study, said. “Water pathways are changing, the ecology is changing, all driven by the declining sea ice field.” 
   
   This article is reproduced with permission from Climate Central. The article was first published on April 6, 2017.
target: – The "Atlantification" of the Arctic Ocean is underway. And no, that doesn't mean we're about to get the polar bear version of Outkast, but rather that the Arctic Ocean is rapidly becoming more like the Atlantic Ocean, according to new research published Thursday. The Arctic Ocean has historically been separated into two layers: a cold, less salty layer on top with a salty, warmer layer of Atlantic water underneath, Scientific American reports. The barrier between the two is called the cold halocline layer, and it's been responsible for preserving Arctic sea ice, according to Science. But the separation between the layers has been quickly breaking down over the past decade or so. The temperature difference between the two layers has lessened by 2 degrees since 2002, and the top layer of cold water has gotten thinner in the past decade—possibly by as much as 180 feet. From 2013 to 2015, the layers merged completely in some areas. The loss of the cold halocline layer means sea ice in the Arctic is getting attacked from both sides. Warming air and warming surface ocean temperatures are creating a "positive feedback loop" that is decimating the ice. Sea ice in the Arctic is decreasing by 13% every decade, and soon the Arctic Ocean could be entirely ice-free during the summer. Between warmer water with more nutrients and no more ice to block the sun, it's unclear what will happen to the Arctic's ecosystem, Inverse reports. (One woman's desperation advanced Arctic exploration.)