Holocene alpine glaciation inferred from lacustrine sediments on northeastern Baffin Island, Arctic Canada'This study helps to address whether mountain glaciers and
small mountain ice caps, which account for the majority of ice
on Baffin Island, and a significant portion of sea-level
rise, were present in the early and middle Holocene. Although it has been documented that small
ice caps on northern Baffin Island disappeared during the
middle Holocene, and the Penny and the Barnes Ice Caps
were present throughout the Holocene , there is very
little knowledge about the history of medium-sized ice bodies
in the eastern Canadian Arctic through the Holocene.'
'Chironomid-inferred summer temperatures from lakes on northeastern Baffin Island and the melt-layer record from the Agassiz Ice Cap define a period between ca. 10.5 and ca. 7ka
with peak summer warmth that was perhaps 5-8C warmer than today (Fisher et al., 1995; Briner
et al ., 2006a; Axford et al., 2009). Other records, like the d18O record from the
Agassiz Ice Cap, show a broader period of warmth between ca. 9 and ca. 3ka (Fisher et al., 1995; Kaufman et al ., 2004). In addition, the peak in abundance of radiocarbon-dated thermophilous molluscs from northeastern Baffin Island occurred between 9.5 and 7.5ka, and then remained elevated until 3.5ka, indicating that surface ocean water between
9.5 and 3.5ka was warmer than today (Dyke et al., 1996a). The discrepancy in early
versus middle Holocene warmth may lie in what theproxy records are recording.Seasonality was high in the early Holocene because of dramatic seasonal differences in solar insolation (Berger and Loutre, 1991). The presence of the shrinking Laurentide Ice Sheet also forced hot summers to remain short (Kaplan and Wolfe, 2006).'
'The sediment records from proglacial lakes reported here
indicate that glaciers in their catchments most likely survived
the early Holocene thermal maximum and were most reduced
between ca. 6 and ca. 3ka. This is an unexpected finding
because summer solar insolation was highest in the early
Holocene and we therefore hypothesise that this would be the
interval of smallest glacier extent.
If glacier extent was
dominated by summer ablation, then glaciers should have
been absent or most reduced during the early Holocene,
perhaps between ca. 10 and ca. 7ka. Although summer
insolation was higher than present in the early Holocene,
seasonality was enhanced. Summers were likely warmer than
today, but also were shorter, due to insolation and the presence
of the Laurentide Ice Sheet (Berger and Loutre, 1991; Kaplan
and Wolfe, 2006), and a short ablation season would have
resulted in less overall glacier melt. Another explanation for
why alpine glaciers may have persisted during this interval of
enhanced warmth is increased precipitation. Although proxy
reconstructions for precipitation are lacking from this region,
warmer surface ocean waters would likely have led to
increased precipitation, and if some of it fell during the long
arctic accumulation season then winter snowfall may have
counteracted the elevated summer ablation.''In any case, decreasing Boreal summer
insolation and Baffin Bay surface temperatures led to
Neoglaciation beginning ca. 3–2ka and a subsequent peak
of glaciation during the LIA. Additional records from proglacial
lakes combined with proxy reconstructions of precipitation that
span the Holocene would greatly improve reconstructions of
Holocene glaciation in the Arctic, and hence knowledge of
alpine glacier sensitivity to climate change.'
