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in the Greenland ice cores [Steffensen et al., 2008; Grachev
and Severinghaus, 2005], rapid changes in North Atlantic
sea surface temperature, advance of the polar front, and sea
ice expansion during the winter in the Northern Hemisphere
[Ruddiman and McIntyre,1981;Sarnthein et al.,2003;
Isarin et al., 2008]. Deepwater proxy records including the
Cd/Ca and Pa/Th ratios [Boyle and Keigwin, 1987; Lippold
et al., 2009, and references therein] have also shown a
weaker ventilation.
Ice advanced during the YD in the Hudson Strait outlet of
the Laurentide Ice Sheet (LIS) [Andrews and MacLean,
2003]. Earlier ice advances and retreats resulted in Heinrich
(H) layers which were dominated by distinctive detrital car-
bonate being deposited in the Labrador Sea and beyond
[Andrews et al., 1993; Dowdeswell et al., 1995; Stoner et
al., 1996]. Andrews et al. [1995] interpreted a H event
(Heinrich layer 0 (H0)) at the time of the YD on the basis
of sparse core data on the southeastern Baf
A marine detrital carbonate record corresponding to H0
was recognized by Andrews et al. [1995] in three closely
spaced cores 20 km off Resolution Island (Figure 1b). An-
drews et al. [1995] also reported the absence of H0 in two
cores (Hu75-55 and Hu75-56) on the lower continental slope
seaward of Hudson Strait and pointed out that H0 was not
generally recognized in deepwater Labrador Sea cores, de-
spite the presence of H1 and older H layers. These authors
also recognized a coeval carbonate-rich layer in several cores
off SE Baf
in Island, in which a high dolomite/calcite ratio
indicated a source from Baffin Island ice [Andrews et al.,
1993, 1995].
On the Labrador Shelf, several Holocene high-carbonate
beds have been recognized. These beds have been correlated
with the Gold Cove and Noble Inlet ice advance/retreat phases
in Hudson Strait [Miller and Kaufman, 1990; Kaufman et al.,
1993; Andrews et al., 1999], the drainage of glacial Lake
Agassiz [Hillaire-Marcel et al., 2007], and the
n Shelf and the
presence of detrital carbonate in cores reported in the litera-
ture from more distal sites. These authors inferred that the
distribution of the H0 bed was predominantly restricted to
the Labrador Shelf.
In this study, we used new northern Labrador Sea cores
data to document the presence of a YD H0 bed in deep water
seaward of Hudson Strait. We reinterpret published data on
the possible extent of the YD signal in the greater Labrador
Sea. These data are used to compare the dispersal of the YD
freshwater discharge with that of H1 seaward of Hudson
Strait and through the Labrador Sea to the North Atlantic
and thus its contribution to abrupt climate change through the
rapidsupplyoffreshwater[Tarasov and Peltier, 2005].
Interpretation of the sedimentology of the H0 and H1 depos-
its provides evidence for the timing and magnitude of fresh-
water discharge during H events, of relevance to the coupled
ice sheet, ocean, and atmospheric modeling studies.
final collapse
of the Foxe ice dome [Barber et al., 1999; Utting et al.,
2007]. The accepted calibrated ages for these events are
10.1
8.4, and 7 ka, respectively [Kaufman
et al., 1993; Thomas et al., 2007; Utting et al., 2007; Rashid
et al., 2008]. Elsewhere on the shelf seaward of Hudson
Strait, any possible H0 layer is either too deep to be pene-
trated by conventional piston coring or is not preserved in
iceberg-scoured terrain or is represented by an unconformity
on the inner part of the shelf [Hall et al., 1999].
Earlier studies have shown that H0 is absent from many
cores on the Labrador Slope and in the deep Labrador Basin
[Andrews et al., 1995; Rashid and Grosjean, 2006; Rashid
and Piper, 2007]. We have compiled the status of H0 in all
available cores from the Labrador Sea in Figure 1a. In most
of these cores, the absence of H0 is not due to a coring
artifact causing core top loss [e.g., Rashid and Grosjean,
2006].
-
10.4, 8.9
-
9.2, 8.2
-
2. ICE MARGINS, ICE EXTENT DURING EARLIER
HEINRICH EVENTS, AND ICE EXTENT AT YD
3. MATERIALS AND METHODS
In this study, we use cores for which the glacial record has
been previously described but in which little attention was
paid to the YD record. Sediment cores Hu97048-16 and
Hu97048-09 (hereinafter Hu97-16 and Hu97-09) [Rashid et
al., 2003a] were retrieved at 1085 and 1575 m water depths,
respectively, from the slopes off Hudson Strait and off Sa-
glek Bank (Figure 1b and Table 1). Core Hu98039-05 (here-
inafter Hu98-05) was retrieved at 5232 m water depth from
the northeastern Sohm Abyssal Plain (SAP), just down
Glacial ice from the large Hudson Bay Basin drained
through Hudson Strait, a narrow graben between Precam-
brian bedrock of Labrador/Nouveau Québec and Baf
n
Island (Figure 1a). Hudson Strait is glacially overdeepened
locally to 900 m and terminates in a shallow sill ranging
from above sea level (Resolution Island) to 450 m depth
(Figure 1b). The strait acted as a conduit in dispersing
glacigenic sediments and meltwater from Hudson Bay to
the Labrador Sea during the last glacial cycle [Andrews and
MacLean, 2003]. Seaward of the sill, a broad transverse
trough up to 600 m deep in Hatton Basin crosses the 250 km
wide shelf.
ow
from the terminus of the Northwest Atlantic Mid-Ocean
Channel (NAMOC) [Piper and Hundert, 2002] (Figure 1a).
Cores were subsampled at 2.5 to 5 cm intervals with 5 cm
3
plastic vials. Wet sediment samples were dried in an oven at
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