A double surge of the Laurentide Ice Sheet during Heinrich Stadial 1
Abstract
Heinrich events (HEs) are major ice rafting events recorded by extensive layers of ice rafted debris (IRD) in a belt across the North Atlantic. The large quantity of meltwater associated with HEs has been proposed as a cause for slowdown of thermohaline circulation, resulting in widespread climate change. HEs are caused by surges of the Laurentide ice sheet through Hudson Strait. The IRD sourced from this region is rich in detrital carbonate (DC). Core scanning XRF can identify layers of DC in marine sediment by their high values of Ca/Sr. Heinrich event 1 (H1) occurs at the onset of the last deglaciation, but the exact relationship between H1 and the cold stadial period between ~19 and 15 ka (referred to as Heinrich Stadial 1 or the Mystery Interval) is uncertain. We present a high-resolution (1 mm) scanning XRF record from IODP site U1308 (50°N 23°W; re-occupation of Site 609) showing that H1 consists of two distinct DC layers. Point counting of IRD grains from the >150um size fraction supports the twin peak observed in the XRF Ca/Sr data. Oxygen isotopes of the bulk carbonate fraction of the sediment reflect the presence of DC and agree with a Laurentide source for the material (Hodell and Curtis, 2008). A similar two-phase peak in IRD has been reported on the Iberian Margin and radiocarbon dated to 16 and 17.5 kyr BP (Bard et al., 2000). Our data support two separate surges of the Laurentide ice sheet during Heinrich Stadial 1, the timing of which may coincide with similar structure observed in other North Atlantic climate records. References D.A. Hodell and J.H. Curtis, Oxygen and carbon isotopes of detrital carbonate in North Atlantic Heinrich Events, Mar. Geol. 256 (2008), 30-35. E. Bard et al., Hydrological impact of Heinrich events in the subtropical Northeast Atlantic, Science 289 (2000), 1321-1324.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMPP53A..06N
- Keywords:
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- 4900 PALEOCEANOGRAPHY;
- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4926 PALEOCEANOGRAPHY / Glacial;
- 4960 PALEOCEANOGRAPHY / Stadial