CGRG Bibliography of Canadian Geomorphology
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Author : Briner, J.P.; Miller, G.H.; Stewart, H.A.; Young, N.; and Anderson, R.
Date : 2009.
Title : New records of Neoglaciation in the northeastern North American Arctic.
Publication : 2009 American Geophysical Union Fall Meeting. December 14-18, 2009. San Francisco, California, USA.
Issue :
Page(s) :
Abstract
Reconstructing patterns of glacier change during the Holocene is important for deciphering regional manifestations of global climate change, characterizing links between climate and cryosphere change, and quantifying the sensitivity of glaciers to climate change. Extensive glaciation in the Arctic during the Little Ice Age (LIA; roughly 1250-1850 AD), however, has left evidence of prior Holocene glacial activity largely obscured. Thus, the most common field evidence of Holocene glaciation in the Arctic are moraines and trimlines created during the maximum phase of the LIA and subsequent retreat during the 20th century. Here, we present the results from two recent studies that have constrained the advance phase of LIA glaciation, and furthermore, placed the relative extent of LIA glaciation into the context of earlier Neoglacial activity. The first site is north-central Baffin Island, where extant ice caps are mere remnants of extensive LIA ice cover. Because the ice caps are cold-based, the pre-glacial tundra surface can be found beneath their receding margins. Populations of radiocarbon ages of tundra vegetation from several of the ice caps reveal periods of rapid ice cap expansion at ~1280 AD and ~1450 AD, but the persistence of some ice caps since at least 350 AD. Lake sediments and in-situ 14C from quartz indicate additional periods of less extensive ice cover earlier during Neoglaciation, beginning at least 3000 years ago. The second site is near Jakobshavn Isbræ, west central Greenland, where we obtained lacustrine sediment cores from lakes in catchments that were partially occupied by the Greenland Ice Sheet (GIS) during the LIA, but which have since become ice-free (“threshold lakes”). Radiocarbon ages from organic-rich (pre-Neoglacial) sediments that lie beneath minerogenic-rich (Neoglacial) sediments reveal the timing of westward expansion of the GIS. Most lakes reveal that following a period of retreat inland of the study sites ~7000 years ago, the GIS approached its Neoglacial maximum ~1400 AD to 1640 AD (during the LIA). One lake, however, suggests that the GIS reached its near-LIA ice limit ~2000 years ago, closer to the timing of the onset of Neoglaciation recorded in regional relative sea level reconstructions. Together, these results are some of very few direct ages of the advance phase of the LIA in the Arctic, and suggest that widespread glacier growth occurred between ~1300-1600 AD. Furthermore, both records register prior Neoglacial activity. These approaches indicate that there is potential to reconstruct Neoglacial activity prior to the maximum phase of the LIA across the eastern Canadian Arctic where cold-based ice caps are receding and throughout western Greenland where proglacial-threshold lakes are abundant.
Bibliography of Canadian Geomorphology