"Heinrich events are armadas of ice," said John Clague of Simon Fraser University in Burnaby, British Columbia, who was not a part of the study. "They are massive discharges of ice." Hendy proposes two explanations for how the Heinrich events in the north Atlantic may have influenced melting in of the Cordilleran Ice Sheet in the Pacific. One possibility is that the Heinrich events triggered sea-level rise, which caused the margins of the Cordilleran Ice Sheet to float up and destabilize. However, there is no strong evidence that a change in sea level occurred at these times. "But there's something going on then, because the corals don't seem to be growing," Hendy said. Another possibility, she said, is that continental temperatures had increased, especially in summertime, leading to calving from both ice sheets. "If you warm up the North American continent, you connect the Laurentide to the Cordilleran," she said. "The relation between the events in the west and the east is good enough that coincidences and accidents won't work," said Richard Alley of Pennsylvania State University in State College, "but I'm not positive whether one can tell whether the [ice debris] is a warming or a cooling signal in the west, or maybe a sea-level signal." Alley thinks sea level is least likely. Understanding the connection between the ice sheets could be helpful for predicting what will happen under today's climate change. "We know that our climate models now can't predict the full amount of climate change that we see," Hendy said, "If we know what the connections were in the past, we could say whether they would happen again." Related Links: Jessica Marshall's blog: EnvironMental Case National Snow and Ice Data Center NASA Images Reveal Greenland Ice Sheet Losing Mass How Stuff Works: If the polar ice caps melted, how much would the oceans rise? |
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