Paper No. 2
Presentation Time: 8:25 AM
MISMATCH OF GLACIER EXTENT AND SUMMER INSOLATION IN SOUTHERN HEMISPHERE MIDLATITUDES
DOUGHTY, Alice M., Department of Earth Sciences, Dartmouth College, HB 6105 Fairchild Hall, Hanover, NH 03755, SCHAEFER, Joerg M., Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, PUTNAM, Aaron E., Lamont-Doherty Earth Observatory, Columbia University, 217 Comer, 61 Route 9W - PO Box 1000, Palisades, NY 10964, DENTON, George, Earth Sciences, University of Maine, Orono, ME 04469, KAPLAN, Michael R., LDEO, Columbia University, Palisades, NY 10964, BARRELL, David, GNS Science, Private Bag 1930, Dunedin, 9054, New Zealand, ANDERSEN, Bjorn, University of Oslo, Oslo, Norway, KELLEY, Samuel, Geology, University at Buffalo, 411 Cooke Hall, University at Buffalo, Buffalo, NY 14260, FINKEL, Robert C., Department of Earth and Planetary Science, University of California, Berkeley, 371 McCone Hall, Berkeley, CA 94720 and SCHWARTZ, Roseanne, Geochemistry, LDEO, Columbia University, Palisades, NY 10964, alice.m.doughty@dartmouth.edu
Here we address a long-standing puzzle of ice-age climate called the "fly in the ointment of the Milankovitch theory". Using geomorphic mapping and surface exposure dating, we find that 10Be ages of moraine boulders from Mackenzie Basin, New Zealand show multiple glacial maxima: 41,760 ± 1090; 35,500 ± 1260; 27,170 ± 680; 20,270 ± 600; and 18,290 ± 490 years old. These maxima span an entire precession cycle suggesting that the behavior of mid-latitude glaciers was not tied to local summer insolation intensity. Instead, we see a closer link between New Zealand glacier expansion and Southern Ocean surface temperatures and atmospheric carbon dioxide.
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