Thursday, April 30, 2015, 4:30PM - 5:30PM
RL-1 room 269
Paleoclimate studies are critical for understanding modern climate change, as they provide
- A contextual understanding of natural climate variability to which modern warming can be compared.
- Opportunities to validate climate models against the paleorecord.
- Insights into the functioning of certain parts of the climate system and estimates of climate sensitivity.
Some of the best archives of past climate change in the climatically sensitive Arctic are glacier moraines, which mark the maximum extent of past glacier advances. Neoglaciation, a period of cooling beginning ~6 ka, was characterized by a series of glacier advances and retreats, culminating in the Little Ice Age advance (~1275-1850 AD), which generally wiped out moraine evidence of the previous, less extensive Neoglacial advances. However, several extant mountain glaciers on Baffin Island, Arctic Canada, are fronted by large, nested moraine sequences that preserve evidence of earliest Neoglacial advances. We dated two of these moraine complexes using 10Be, a cosmogenic radionuclide, to constrain the timing of these early Neoglacial advances. Nine 10Be ages from the distal portion of a composite moraine at Snow Creek Glacier range from ~1.8 ka to ~5.7 ka, and twelve ages from the two most distal moraine crests at Throne Glacier range from ~1.1 ka to ~4.6 ka. We interpret the wide spread of ages in these settings to indicate post-emplacement moraine degradation due to ice core melting and subsequent readvances disturbing moraine boulders. Because these processes result in the exposure of fresh boulder faces at a moraine crest through time, effectively resetting the 10Be clock, the oldest ages in these datasets likely represent a minimum age for the initiation of moraine formation. Additionally, we explore the moraine-forming process in these settings using a numerical glacier model that accounts fro the effect of debris cover on the glacier surface.