“The character of these far-ranging changes,confirmed by our statistical analyses,provides a convincing case for tipping points(临界点)being crossed,”wrote researchers led by the scientist Susanne Kortsch who studies life in the sea.For scientists,tipping points aren’t just pop-culture shorter way of saying,but refer to a specific type of conversion:happen quickly and not develop from one thing to another in a single smooth series of stages,with one set of conditions translating into another.
About life in the sea,that’s been seen in the western Mediterranean,now controlled by animals with no backbone,and Caribbean coral reefs(珊瑚礁)now filled by algae.As for the Arctic,they’ve been discovered,but mostly on land or in freshwater lakes and swamps.
Kortsch and her University of Tromso colleagues went to sea,examining two Arctic bays(海湾)in the western Svalbard islands.Researchers have studied those bays for more than three decades.Between 1980 and 2010,the region’s summer ice-free season lengthened by an average of 3.3 days per year.
“Such changes aren’t simple,”say Kortsch’s group.They’re what ecologists call regime shifts(稳态转换),in which one set of plants and animals is almost entirely replaced by another.They’re not limited to two bays but appear on much of the Arctic Ocean’s shores,either.How will these changes influence food chains?It stands to reason that some changes will occur,but accurate data is needed.“At present,we simply don’t know the answers,”Kortsch said.
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