¹⁰Be Surface-Exposure Chronology of the Tres Hermanos and Rosa Irene Moraines Near Bahía Inútil, Chilean Patagonia
What caused the termination of the last ice age in the Southern Hemisphere? During the last termination, massive glacial collapse occurred in the southern midlatitudes during a period of decreasing local summer insolation intensity. The inability of local changes in summer insolation to explain this...
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DigitalCommons@UMaine
2014
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| Online Access: | https://digitalcommons.library.umaine.edu/etd/2078 https://digitalcommons.library.umaine.edu/context/etd/article/3112/viewcontent/LennonJR2014_OCR.pdf |
| Summary: | What caused the termination of the last ice age in the Southern Hemisphere? During the last termination, massive glacial collapse occurred in the southern midlatitudes during a period of decreasing local summer insolation intensity. The inability of local changes in summer insolation to explain this observed climate change in the Southern Hemisphere points to other forcing mechanisms for the termination. For example, a new hypothesis for the termination has emerged in which melting and collapse of Northern Hemisphere ice sheets lead to growth of North Atlantic sea ice, southward shift of the intertropical convergence zone (ITCZ), poleward movement of the southern westerly wind belts and associated ocean fronts (Anderson et al., 2009), and abrupt warming in the southern mid-latitudes (Denton et al., 2010). In particular, two pulses of warming that together make up most of the Southern Hemisphere termination have been linked to Northern Hemisphere cold events, Heinrich Stadial 1 (HS-1) and the Younger Dryas. Carbon dioxide emitted from the Southern Ocean during these two events may have been instrumental in driving the end of the ice age to completion. If the hypothesis stated above holds true, then warming in the Southern Hemisphere (Termination 1) would occur at the same time as cooling in the Northern Hemisphere (Heinrich Stadial 1). Testing this hypothesis and others of the last termination requires detailed and well-dated glacial and paleoclimate reconstructions from both hemispheres in order to compare the timing and spatial pattern of climate events with potential forcing mechanisms. The goal of this project was to reconstruct the glacial history of Bahía Inútil, in the Strait of Magellan region of Patagonia, in order to constrain the timing of the onset of the termination in the middle latitudes of South America. Field work consisted of mapping the glacial geomorphology of prominent moraine belts on the south side of Bahía Inútil at two field sites, Estancia Tres Hermanos (ETH) and Estancia Rosa Irene ... |
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