During the late 1980s through the mid 1990s, these natural variations got stuck in a phase that generated winds to drive large amounts of ice through the Fram Strait and out into the Greenland Sea, explains Walter Meier, a researcher with the National Snow and Ice Data Center in Boulder, Colo. In addition, warmer water from the Atlantic and Pacific has been moving north into the Arctic Basin.
"Since that period, we haven't seen a persistently strong Arctic Oscillation," he said during a briefing this morning. He was referring to the natural climate pattern involved. More recently, this pattern has entered a neutral or slightly weak phase. But, he adds, "we're still losing the summer ice and losing the thicker ice cover."
The persistently strong pattern toward the end of the last decade "may have played a role in triggering the loss of ice cover," he continued. But "it certainly is not the overriding factor in terms of long-term loss."
Going into this past winter, researchers say, things appeared to be looking up at the top of the world. The winter began with a larger inventory of two-year ice than the year before. But during the winter, much of that "tweenage" ice blew out through the Fram Strait toward lower latitudes and melted. This boosted the proportion of single-year ice in the Arctic.
The multitrillion dollar question: What happens next?