Heinrich Event
IRD
Heinrich in Spektrum (deutsch)
Deep-sea sediment cores recovered from the Northeast Atlantic Ocean were examined in order to elucidate the influence of the Earth’s orbital parameters on major ice rafting. Analyses of coarse-grained ice-rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal. Since 130,000 yr B.P., dropstone layers have been deposited each half period of a precessional cycle (11,000 ± 1000 yr). Ice rafting occurs during times of winter minimum/summer maximum insolation and summer minimum/winter maximum insolation. In the first case, high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter. In the second case, growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater. Both situations result in a southward penetration of polar water. Thus, the marine record of dropstones documents ice rafting not only during Weichselian stades but also during cold events within interstades. The regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes, not only in the region of the North Atlantic Ocean but also in remote areas such as the Pacific Ocean and the Antarctic.
SEDIMENTS in the North Atlantic ocean contain a series of layers that are rich in ice-rafted debris and unusually poor in foraminifera1. Here we present evidence that the most recent six of these ‘Heinrich layers’, deposited between 14,000 and 70,000 years ago, record marked decreases in sea surface temperature and salinity, decreases in the flux of planktonic foraminifera to the sediments, and short-lived, massive discharges of icebergs originating in eastern Canada. The path of the icebergs, clearly marked by the presence of ice-rafted detrital carbonate, can be traced for more than 3,000 km—a remarkable distance, attesting to extreme cooling of surface waters and enormous amounts of drifting ice. The cause of these extreme events is puzzling. They may reflect repeated rapid advances of the Laurentide ice sheet, perhaps associated with reductions in air temperatures, yet temperature records from Greenland ice cores appear to exhibit only a weak corresponding signal. Moreover, the 5–10,000-yr intervals between the events are inconsistent with Milankovitch orbital periodicities, raising the question of what the ultimate cause of the postulated cooling may have been.
The real fortune was that Heinrich, following on the recent nonsense idea to dispose of nuclear waste into the sea, then stumbled with paleoclimate in the form of basalt stone and then just researched.