Abstract
Abstract. In 2013 an ice core was recovered from Roosevelt Island, an ice dome between two submarine troughs carved by paleo-ice-streams in the Ross Sea, Antarctica. The ice core is part of the Roosevelt Island Climate Evolution (RICE) project and provides new information about the past configuration of the West Antarctic Ice Sheet (WAIS) and its retreat during the last deglaciation. In this work we present the RICE17 chronology, which establishes the depth–age relationship for the top 754 m of the 763 m core. RICE17 is a composite chronology combining annual layer interpretations for 0–343 m (Winstrup et al., 2019) with new estimates for gas and ice ages based on synchronization of CH4 and δ18Oatm records to corresponding records from the WAIS Divide ice core and by modeling of the gas age–ice age difference. Novel aspects of this work include the following: (1) an automated algorithm for multiproxy stratigraphic synchronization of high-resolution gas records; (2) synchronization using centennial-scale variations in methane for pre-anthropogenic time periods (60–720 m, 1971 CE to 30 ka), a strategy applicable for future ice cores; and (3) the observation of a continuous climate record back to ∼65 ka providing evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.
Highlights
The Roosevelt Island Climate Evolution (RICE) project seeks to combine geophysical measurements with climate information from a well-dated ice core to improve constraints of the glacial history of the eastern Ross Sea (Conway et al, 1999)
We advise caution when interpreting the absolute values of total air content (TAC) from the RICE ice core due to the potential artifacts caused by gas loss through fractures and the large uncertainty in the cut-bubble correction
Continuity of the RICE ice core appears to end at 746.00 m below surface, where a discontinuity of 20 ‰ is observed in the δD record (746.00–746.10 m) (Fig. 6b), and a 0.35 ‰ change is observed between sequential δ18Oatm samples (745.81 and 746.20 m) (Fig. 6c)
Summary
The Roosevelt Island Climate Evolution (RICE) project seeks to combine geophysical measurements with climate information from a well-dated ice core to improve constraints of the glacial history of the eastern Ross Sea (Conway et al, 1999). For the 343.7–754 m section of the RICE ice core, the best age constraints are from measurements of methane and the isotopic composition of molecular oxygen (δ18Oatm). Variations in these parameters are globally synchronous (Bender et al, 1994; Blunier et al, 1998), meaning that, to a first order, different ice cores will record the same atmospheric history. With support from measurements of total air content (TAC), to interpret that the Roosevelt Island ice dome was stable throughout the last glacial maximum
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