Thursday, March 06, 2014, 4:30PM - 5:30PM
RL-3 room 248
In situ dead vegetation emerging from beneath cold based ice in the eastern Canadian arctic have been shown to provide important constraints on ice fluctuations during the Holocene and perhaps even earlier (Anderson et al., 2008; Miller et al., 2013). During the summer of 2013, we conducted a sampling campaign in the Cumberland Peninsula area of south eastern Baffin Is, Nunavut, CA in an effort to better constrain ice fluctuations in the region back through the last interglacial (~125 ka). In August, during the peak of the melt season, we visited 88 sites along the margins of the Penny Ice Cap and other local ice bodies, collecting 184 samples of in situ dead vegetation (mainly Polytrichum mosses) emerging from under the ice edge. The cold-based nature of the ice in this region means that the land surface underneath the ice is largely undisturbed and mosses and lichens remain in the position they were growing in when the snowline dropped below the site, entombing the plants. Thus the 14C age of these plants is interpreted as the time when ice growth resulting from summer cold killed the vegetation, providing important constraints of past climates. Therefore, the "kill date" for each plant records when cold summers dropped regional snowline below the site, and remained below until our collection date. The kill dates also represent the last time that the climate was warm enough to expose the sampling location. Ultimately these ages, in combination with other methods, provide a powerful tool for reconstructing past glacial histories and investigating possible mechanisms of ice cap changes in this region of the Arctic.