Leading Edge / Spring 2005
The Iceberg Cometh

Ocean tides dislodged huge Arctic icebergs, contributing to climate cooling thousands of years ago


Labrador Sea ocean tides dislodged huge Arctic icebergs thousands of years ago, carrying gigantic ice-rafted debris across the ocean and contributing to the Ice Age’s deep freeze. The study, published in Nature, is the first to suggest that ocean tides contributed to Heinrich events – a phenomenon where colossal discharges of icebergs periodically flowed into the North Atlantic from about 60,000 to 10,000 years ago.

U of T physics professor Jerry Mitrovica, lead author Professor Brian Arbic of Princeton University and a team of researchers used a new computer model that accurately captures current open-ocean tides. They then inputted ice-age simulations of sea-level changes over time. “The results showed that the tides were highest in the Labrador Sea at the same time the Heinrich events occurred,” says Mitrovica. “We can safely assume that the tides played a key role in breaking the ice and launching the icebergs in the ocean.”

“These findings provide a link between ocean tides, ice sheets and ocean circulation and a measure of the sensitivity of climate during the last Ice Age,” he says. “This sensitivity is important to understand, because the connection between changes in ocean circulation and future climate remains a matter of great interest.”


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