A High Resolution Record of the Eemian Interglacial and Transition to the Next Glacial Period from Mount Moulton (West Antarctica)
As of 2002, Degree of Master of Science (MS) Quaternary and Climate Studies published under the auspices of the Climate Change Institute.
Soluble major ions (Cl-, NO3-, SO42-), trace elements (Na, Ca, K, Li, Zn, Pb, Hg, Cd, Cu, V, Mn, Ni, As, Al, Fe, Se, and REEs) and water hydrogen isotopes (5D) were measured along a ~40-meter horizontal ice core from Mt. Moulton Blue Ice Area (BIA) in West Antarctica at a temporal sample resolution of ~6.5-7 years. The melted section covers the period from 107 to 136 ka BP, based on 40Ar/39Ar radiometric dates from three englacial tephra layers dated by Dunbar et al. (2008), thus overlapping onset and termination of the Eemian. The resulting time-series provides a first high-resolution record of the Eemian interglacial and transition to the subsequent glacial period from Antarctica and the first glaciochemical record for this period from West Antarctica. The Mt. Moulton deuterium record matches well (r = 0.62-0.84, >99.9%) with isotope records from East Antarctic deep ice cores (Vostok, Dome Fuji, EPICA Dome C and Taylor Dome). The major difference between Mt. Moulton and water isotope records from these other ice cores is between ~110-120 ka B.P.. While all East Antarctic records show a continual decline in the isotope time series, the Moulton deuterium record is relatively stable, most likely due to the stronger and more consistent oceanic influence on the Mt. Moulton site. All Mt. Moulton chemical concentrations were higher during glacial conditions than during the Eemian interglacial, likely due to increased atmospheric circulation (dust elements, seasalts aerosols), increased sea ice extent (Na, nssSO42-) and increased oceanic productivity (nssSO42-) during the glacial period. The interpretation of the Mt. Moulton δD, seasalts, nssSO42- and dust records suggests that the Eemian began -134.3 ka B.P. and lasted approximately 10,500-15,300 years. Comparison of the Mt. Moulton Eemian with the Holocene records does not reveal any major cold events such as the Antarctic Cold Reversal (ACR) and suggests that the Eemian deglaciation was uninterrupted by major changes in climate on the scale of the ACR. The Mt. Moulton dust record does reveal several periods of increased activity during the Eemian that lasted -120-400 years. These events may reflect abrupt changes in atmospheric circulation and are similar, but notably shorter in duration than the rapid climate change events in other Holocene ice core records from Greenland such as the period of intensified atmospheric circulation ~6-5 ka B.P..