2007: Mixed-layer deepening during Heinrich events: A multi-planktonic foraminiferal d 18 O approach
extreme climate swings of a few decades to millennia during the last glacial cycle, including periods of intense ice rafting called Heinrich events (HEs). We have found similar oxygen isotope variations recorded inmixed-layer – and thermocline-dwelling planktonic foraminifera during HEs 0, 1, and 4,...
| Main Authors: | , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.515.4847 http://boyle.mit.edu/~ed/pdfs/rashid(2007)science318_439.pdf |
| Summary: | extreme climate swings of a few decades to millennia during the last glacial cycle, including periods of intense ice rafting called Heinrich events (HEs). We have found similar oxygen isotope variations recorded inmixed-layer – and thermocline-dwelling planktonic foraminifera during HEs 0, 1, and 4, suggesting that three foraminiferal taxa calcified their shells at similar temperatures in a homogenized upperwater column. This implies that the surface mixed layer was deeper during HEs. Similar deepening occurred on the northern margin of the ice-rafted–debris belt, implying that these deep mixed layers during HEs were widespread in the region. We suggest that an increase in storminess during HEs intensified the vertical mixing of meltwater from ice rafting in the upper ocean. Late Pleistocene Heinrich events (HEs)(1–3) in the North Atlantic are identifiedby distinct ice-rafted–detritus (IRD) layers primarily derived from the Laurentide Ice Sheet (4). Eight such events coincided with the coldest, stadial phase of some Dansgaard-Oeschger (D/O) events inGreenland ice cores over the past ~65,000 years. D/O events typically start with an abrupt 9 to 15°C (5) warming over a few decades or less |
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