Master's thesis defence by Isabell Lubanski – Københavns Universitet

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Master's thesis defence by Isabell Lubanski

d180 of O2 in RICE ice core

In a warming world, estimates of how much the West Antarctic Ice Sheet will contribute to future sea level rise, are important to make projections for future climate. The coastal RICE ice core fromthe Ross Ice Shelf inWest Antarctica can help to improve our understanding of, among others, what drives ice sheet retreat and collapse.

The residence time of ±18O in the atmosphere of 1200-2000 years is significantly larger than the one year time scale of interhemispheric mixing, so ±18O is a global marker. ±18O bears a strong signature of orbital precession and has therefore been used to orbitally tune different ice core records.

In this master project, we finalize and test an existing experimental set-up for measuring atmospheric ±18O conserved in bubbles in ice cores.

We measure ±18O for 18 different depths in the oldest part of the RICE ice core. Our measurements are superimposed on the Siple Dome ice core ±18O record in order to find the age of the gas. An a priori dating is performed using the RICE measurements that fit with well-defined peaks in the ±18O record from the Siple Dome core to constrain the other measurement points in time intervals.

No time scale can be determined for the oldest 30 m of the RICE core because there are too few data points to constrain our measurements to a certain time interval. The a priori time scale is improved for the interval 696.2 m - 728.3 m using methane data from the RICE core. Our time scale dates 728.3mto 36,000 years BP.

Supervisor: Thomas Blunier, Professor, Centre for Ice and Climate
Co-supervisor: Corentin Reutenauer, Research Assistant, Centre for Ice and Climate