B

x 10

2 x 104 3 x 104 Cal years BP

x 10

2 x 104 3 x 104 Cal years BP

55 50 45

0 40

25 20

20 25 30 35 40 45

HU87-009

HU87-009

35 45

Figure 21.9 (a) GISP2 S18O data, with 1470-yr band-pass filter. (b) Solar radiation at 65°N in July. (c) Multitapered (MTM) spectra. Data for (c) and (d) from Blosseville Basin and Labrador Sea—D-O events. Notice the different age scales. The arrows in (c) and (d) link possible correlative events (see Fig. 21.3 for location of cores).

20 25 14C ka

35 45

Figure 21.9 (a) GISP2 S18O data, with 1470-yr band-pass filter. (b) Solar radiation at 65°N in July. (c) Multitapered (MTM) spectra. Data for (c) and (d) from Blosseville Basin and Labrador Sea—D-O events. Notice the different age scales. The arrows in (c) and (d) link possible correlative events (see Fig. 21.3 for location of cores).

21.3.3.2 The Cockburn enigma

One of the world's longest moraine complexes runs from the northern tip of Labrador northward across the fjord heads on eastern Baffin Island, on to Melville Peninsula, and thence across the Arctic mainland where it lies close to the marine limit (Fal coner et al., 1965; Blake, 1966; Andrews & Ives, 1978; Andrews, 1989) (Fig. 21.3). The moraine complex is dated by marine shells found in associated raised glacial marine deltas (Andrews, 1989, fig. 3.75, p. 294) at around 8 14Ckyr BP and are referred to as the Cockburn Moraines (Ives & Andrews, 1963). The Cockburn Moraines post-date the last major readvance of Labrador ice across Hudson Strait during the Noble Inlet advance 8.4-8.9 ka

(MacLean et al., 2001; Jennings et al., 1998; Manley & Miller, 2001) and they appear to pre-date the 8.2 cal.kyr cold event associated with the final break-up of the LIS in Hudson Strait and Hudson Basin (Barber et al., 1999; Clarke et al., 2004). The Cock-burn readvance represents a positive change in the northeast LIS's mass balance, which appears to be coeval with the introduction of a 'warm' mollusc fauna into Baffin Bay (Andrews, 1972; Dyke et al., 1996). However, the Cockburn Moraines invariably lie close to a marine limit or at a fjord head, so the apparent positive change in mass balance might be caused by the reduction in calving (mass loss) as the ice sheet retreated from a tidewater- to land-based situation (Fig. 21.2B) (cf. Hillaire-Marcel et al., 1981). Hence the lack of a correlation with any changes in temperature or accumulation on the nearby Greenland Ice Sheet (Fig. 21.3) might argue for a non-climatic but dynamic driving force.

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