Heinrich Events In the 1980s, the German paleoceanographer Hartmut Heinrich ( Heinrich , 1988 ) extracted samples at regular increments from northeastern Atlantic sediment cores that had been retrieved by drilling into the ocean floor. He analyzed his samples and determined their lithic content and their content of planktonic foraminifera fragments. He found that the relative numbers of lithics (sand, stones, etc.) and foraminifera fluctuated in a surprising manner and that the transitions between lithic-dominated (light-colored) and foraminifera-dominated (dark-colored) sediments were unexpectedly abrupt.
These phases with sudden increases in the amount of lithics have subsequently been termed “Heinrich events” ( Broecker et al., 1992 ). The key features of sediment delivery during Heinrich events are the presence of icebergs, meltwater plumes, and massive gravity flows (turbidites). The iceberg-rafted debris accumulated on the ocean floor every 5–10 thousand years during the last glacial period. These processes, which are associated with cold events (stadials), produce sediments with a high lithic content, whereas the foraminifera-rich non-Heinrich sediments were deposited during warmer (interstadial) periods.The lithic sediments of Heinrich events, which contain iceberg-rafted detritus, have a high carbonate content that is probably derived from the source region of Paleozoic limestones and dolomites in eastern Canada and possibly northwestern Greenland ( Bond et al., 1992 ).
This suggests that the lithic sediments of the Heinrich events were excavated by the Hudson Strait ice stream, which drained a large part of the former Laurentide ice sheet. Rapid fluctuation in this ice stream not only produced the sudden Heinrich events (of which there have been 6 over 60 thousand years) but also led to the creation of plumes of extre-mely fresh glacial meltwater. These flowed into the normally salty North Atlantic and so would have affected the thermohaline circulation in the North Atlantic, which could in turn cause abrupt climatic changes far afield. Abrupt dusty events at low latitudes appear to have been broadly synchronous with high-latitude Heinrich events ( Jullien et al., 2007 ).
Hibliography Anderson, D., A. S. Goudie , and A. G. Parker . Global Environments through the Quaternary. Oxford and New York: Oxford University Press, 2007 . Bond, G., et al. “Evidence for Massive Discharges of Icebergs into the North Atlantic during the Last Glacial Period.” Nature 360 ( 1992 ), pp.245–249. Broecker, W. S., et al. “Origin of the Northern Atlantic's Heinrich Events.” Climate Dynamics 6.3–4 ( 1992 ), pp.265–273. DOI: 10.1007/BF00193540. Bryant, E. Climate Process and Change. Cambridge and New York: Cambridge University Press, 1997 . Heinrich, H. “Origin and Consequences of Cyclic Ice Rafting in the Northeast Atlantic Ocean during the Past 130,000 Years.” Quaternary Research 29.2 ( 1988 ), pp.143–152. DOI: 10.1016/0033-5894(88)90057-9. Jullien, E., et al. “Low-Latitude ‘Dusty Events’ vs. High-Latitude ‘Icy Heinrich Events’.” Quaternary Research 68.3 ( 2007 ), pp.379–386. DOI: 10.1016/j.yqres.2007.07.007. Andrew S. Goudie
How to cite this entry: Andrew S. Goudie "Heinrich Events" The Oxford Companion to Global Change. Ed. David Cuff and Andrew Goudie. Oxford University Press, 2009. Oxford Reference Online. Oxford University Press. 2 February 2012
