Quote of the Day: “Oceans have long memories”

BBC report on the melting of the Greenland ice sheet

This week’s Rolling Stone has a devastating article on the almost unbelievable rate of melting of the Greenland and Antarctic ice sheets.  Here’s a particularly hair raising excerpt:

In the past few years, scientists have begun to worry that the world’s glaciers have entered what they call a “runaway feedback mode,” in which the dramatic changes to the water and wind and ice caused by global warming have not only accelerated but have themselves begun to alter the climate, creating a dynamic that could be irreversible. Both Antarctica and Greenland are now losing ice at twice the rate they were in 2002 — as much as 400 billion tons each year. In July, after the planet’s six warmest months on record, a giant crack opened up overnight in the Jakobshavn Glacier; for the first time ever, scientists monitoring satellite data were able to observe in real time as an iceberg covering 2.7 square miles broke off and floated into the sea. Three weeks later, an even larger iceberg — four times the size of Manhattan — cleaved away from another glacier to the north of Jakobshavn, stunning scientists who study the ice sheets. “What is going on in the Arctic now,” says Richard Alley, the geoscientist at Penn State, “is the biggest and fastest thing that nature has ever done.”

Scientists say that oceans have long memories. The water reflects the slow-spreading response to events that took place a month, a year, a hundred years ago. An earthquake in the Arctic. A cyclone in the Bay of Bengal. A particularly strong El Niño summer, a decade and a half in the past. These memories are not all known, and their physics are not perfectly mapped, so the movements of the oceans are not well understood. “The ice sheet,” Bindschadler says, “really is just the tail of the dog.” There remains the chance that cutting carbon emissions might, in the long term, prevent more warm water from getting into the Amundsen Sea, where it is melting the ice shelves. If the atmospheric system really does have dials, in other words, then perhaps they can be turned to more comfortable settings. “That may be the saving grace,” Bindschadler says. But even if we reduce emissions, he warns, there is no way to get the heat that is already in the ocean, melting the ice, back out.

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