Orbital forcing of West and East Antarctic ice sheets 3.8-3.0 Ma; a climate analogue in Weddell Sea ODP Site 697

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Author(s): Cullen, Kate
Source: 103p. Institution: Wesleyan University, Middletown, CT, United States
Note: In English. Includes appendices. 101 refs. Bachelor's thesis
Summary: As climate change intensifies and the world begins to feel its impacts, scientists are looking to past climatically similar periods to understand how our planet will respond. During the Pliocene Epoch (5.33-2.58 millions of years ago), the West Antarctic Ice Sheet (WAIS) nearly de-glaciated under peak CO2 concentrations of ∼400 ppm (Fedorov et al., 2013) and global average temperatures 2-3°C warmer than pre-industrial values (Yamane et al., 2015). The sensitivity of the WAIS to CO2 and ocean temperature fluctuations on orbital timescales is well established (DeConto & Pollard, 2003; Naish et al., 2009). A more controversial question is how sensitive the East Antarctic Ice Sheet (EAIS) is to similar forcings. To address this question, we analyze sedimentological changes in Antarctic Weddell Sea ODP Site 697 marine cores deposited 3.8-3.0 Ma for cyclicities in ice sheet dynamics and bottom water fluctuations. Spectral analysis of fine fraction mineral assemblages identifies smectite, illite, chert, chalcedony, SiO2, garnet and feldspar. Continuous detrital smectite deposition points to high Antarctic Bottom Water (AABW) circulation through the Jane Basin 3.8 to 3.0 Ma. Varimax-rotated principal component analysis and wavelet analysis of elemental count ratios suggest Jane Basin sediment deposition transitioned from a dominant eccentricity forcing with obliquity inputs to a dominant precession forcing modulated by eccentricity at ∼3.3 Ma. Derived linear sedimentation rates slow from ∼6.3 cm/kyr between 3.78 and 3.21 Ma to 4.74 cm/kyr between 3.14 and 3.03 Ma. These findings indicate that EAIS and WAIS behavior as moderated by an eccentricity and obliquity forcing during Pliocene peak warming and a precession forcing during cooler conditions after ∼3.3 Ma.
Year of Publication: 2016
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 20 Geophysics, Applied; Antarctic ice sheet; Antarctica; Carbon dioxide; Cenozoic; Chalcedony; Chemically precipitated rocks; Chert; Clay minerals; Climate change; Climate forcing; Cores; East Antarctic ice sheet; Electron microscopy data; Framework silicates; Illite; Leg 113; Magnetostratigraphy; Mineral assemblages; Neogene; ODP Site 697; Ocean Drilling Program; Orbital forcing; Paleoclimatology; Pliocene; SEM data; Sedimentary rocks; Sheet silicates; Silica minerals; Silicates; Smectite; Southern Ocean; Spectra; Spectral analysis; Temperature; Tertiary; Wavelets; Weddell Sea; West Antarctic ice sheet; X-ray fluorescence spectra
Coordinates: S614838 S614837 W0401743 W0401744
Record ID: 2018001949
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