Heinrich events

Some scientists have suggested that the Dansgaard-Oeschger events are related to the Heinrich events. Hartmut Heinrich, a marine geologist, described these events as episodes during the last ice age when major icebergs cleaved off ice sheets and drifted to sea. His proof of this was found in ocean-bottom sediment cores that contain the eroded sediments the ice had originally scoured and carved off the landmasses as it moved over land. He claimed that as the icebergs melted and added freshwater to the oceans, they interrupted the major ocean currents. In particular, he believed they interrupted the Atlantic thermohaline current, the key current that transports heat from the equatorial area to the

North Atlantic. The addition of freshwater slows the current, destroying its heat-carrying capacity and significantly cooling the Northern Hemisphere. This, in turn, was enough of a change to cause the cycle of warming and cooling seen in the Dansgaard-Oeschger events because cooler climate causes the ice cover to increase. When ice cover increases, so does surface albedo, which, as a positive feedback, promotes further ice growth and additional cooling.

0 0

Post a comment