A team of NASA and university scientists has detected an ongoing reversal in Arctic Ocean circulation triggered by atmospheric circulation changes that vary on decade-long time scales. The results suggest not all the large changes seen in Arctic climate in recent years are a result of long-term trends associated with global warming.  “Our study confirms many changes seen in upper Arctic Ocean circulation in the 1990s were mostly decadal in nature, rather than trends caused by global warming,” said Morison.  While some 1990s climate trends, such as declines in Arctic sea ice extent, have continued, these results suggest at least for the ‘wet’ part of the Arctic—the Arctic Ocean—circulation reverted to conditions like those prevalent before the 1990s,” he added.  During its strong counterclockwise phase in the 1990s, the Arctic environment changed markedly, with the upper Arctic Ocean undergoing major changes that persisted into this century. Many scientists viewed the changes as evidence of an ongoing climate shift, raising concerns about the effects of global warming on the Arctic. Read more here.