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importance of total freshwater discharge and the duration of
freshwater discharge in H0 compared to H1 in controlling the
isotopic signature of surface water. The other complication
with the
different impact on the world ocean as a result of differences
in ice stream margin extent.
18
O
Nps
signal is the competing effect of temperature,
especially during YD, when the ice margin configuration and
the temperature were different than during H1, which may
have minimized the depleted
δ
Acknowledgments. We would like to thank L. Polyak for his
comments on the earlier version of the manuscript. H. Rashid was
partially supported by the Byrd Polar Research Fellowship during
the study. This is Geological Survey of Canada contribution
20090094.
18
O
Nps
values resulting from
the freshwater input. One of the vexing problems with records
like Hu97-09 and Hu97-16 is the absence of enough plank-
tonic foraminifera, preventing paired Mg/Ca and
δ
REFERENCES
18
Omea-
surements in the N. pachyderma (s), which could shed light
on the relative contribution from temperature and fresh water
[Rashid and Boyle, 2004]. It is possible that the newer gen-
eration of ICP-MS or newer method requiring smaller sam-
ples might allow isolation of the seawater
δ
Addington, L. D., S. A. Kuehl, and J. E. McNinch (2007), Con-
trasting modes of shelf sediment dispersal off a high-yield river:
Waiapu River, New Zealand, Mar. Geol., 243,18
30.
Alley, R. B., and P. U. Clark (1999), The deglaciation of the
Northern Hemisphere: A global perspective, Annu. Rev. Earth
Planet. Sci., 27, 149
-
18
O signal from
δ
18
O
Nps
, and this possibility needs to be explored in future
studies.
the
δ
182.
Alley, R. B., and D. R. MacAyeal (1994), Ice-rafted debris associ-
ated with binge/purge oscillations of the Laurentide Ice Sheet,
Paleoceanography, 9, 503
-
6. CONCLUSIONS
511.
Andrews, J. T., and B. MacLean (2003), Hudson Strait ice streams:
A review of stratigraphy, chronology and links with North
Atlantic Heinrich events, Boreas, 32,4
-
The H0 carbonate-rich sediment layer in the northeastern
Labrador Sea corresponds to YD supply of sediment and
fresh water through Hudson Strait. H0 is ~1 m thick on the
northern Labrador Slope, implying a large supply of sedi-
ment and concomitant freshwater discharge. The sedimen-
tology of this layer closely resembles that of H1 and H2, but
its distribution is quite different. The H0 layer is restricted to
a small area in the northwestern Labrador Sea, and correla-
tive carbonate-rich turbidites are recognized locally in the
northeastern SAP. H0 sediment is generally absent in the
deep Labrador Sea. Turbidity currents may have flowed
hyperpycnally or resulted from plume fallout or slumping of
slope sediments from sediment-rich freshwater outbursts that
occurred as ice was blocked by the sill at the mouth of
Hudson Strait. A sediment plume was transported southward
along the Labrador Shelf edge, with deposits recognized in
the Orphan Basin, suggesting that the Labrador Current flow
may have been similar to the present. The duration of this
plume
17.
Andrews, J. T., K. Tedesco, and A. E. Jennings (1993), Heinrich
events: Chronology and processes, east-central Laurentide Ice
Sheet and NWLabrador Sea, in Ice in the Climatic System, NATO
ASI Ser., vol. l, edited by R. Peltier, pp. 167
-
-
186, Springer,
New York.
Andrews, J. T., A. E. Jennings, M. Kerwin, M. Kirby, W. Manley,
G. H. Miller, G. Bond, and B. MacLean (1995), A Heinrich-like
event, H-0 (DC-0): Source(s) for detrital carbonate in the North
Atlantic during the Younger Dryas chronozone, Paleoceanogra-
phy, 10, 943
952.
Andrews, J. T., L. D. Keigwin, F. Hall, and A. E. Jennings (1999),
Abrupt deglaciation events and Holocene palaeoceanography
from high-resolution cores, Cartwright Saddle, Labrador Shelf,
Canada, J. Quat. Sci., 14, 383
-
397.
Bakke, J., Ø. Lie, E. Heegaard, T. Dokken, G. H. Haug, H. Birks,
H. P. Dulski, and T. Nilsen (2009), Rapid oceanic and atmospher-
ic changes during the Younger Dryas cold period, Nat. Geosci.,
12, 202
-
205.
Barber, D. C. (2001), Laurentide Ice Sheet dynamics from 35 to 7
ka: Sr-Nd-Pb isotopic provenance of NW North Atlantic margin
sediments, Ph.D. thesis, Univ. of Colo., Boulder.
Barber, D. C., et al. (1999), Forcing of the cold event of 8,200 years
ago by catastrophic drainage of Laurentide lakes, Nature, 400,
344
-
flow was probably less than in H1, resulting in a much
thinner distal deposit. Lack of a significant depleted oxygen
isotopic signal in the planktonic foraminifera during the H0
could be in part due to the competing temperature and cold
freshwater effects, which could be pursued in future studies.
The differences in sediment distribution between H0 and
earlier H events are a consequence of the ice margin not
extending as far seaward during H0. As a result, sedimenta-
tion and freshwater supply during H0 were dominated by
freshwater outbursts from behind the Hudson Strait sill,
whereas in H1, this process was important only during the
late stages of the event. Rapid ice retreat and meltwater
supply from the same ice stream may thus have a very
348.
Benetti, S. (2006), Late Quaternary sedimentary processes along the
western North Atlantic margin, Ph.D. thesis, Natl. Oceanogr.
Cent., Southampton, U. K.
Bond, G. C., W. Showers, M. Cheseby, R. Lotti, P. Almasi, P.
deMenocal, P. Priore, H. Cullen, I. Hajdas, and G. Bonani
(1997), A pervasive millennial-scale cycle in North Atlantic
Holocene and glacial climates, Science, 278, 1257
-
-
1266.
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