Continuous-Flow Analysis Of Delta O-17, Delta O-18, And Delta D Of H2o On An Ice Core From The South Pole

The delta D and delta O-18 values of water are key measurements in polar ice-core research, owing to their strong and well-understood relationship with local temperature. Deuterium excess, d, the deviation from the average linear relationship between delta D and delta O-18, is also commonly used to provide information about the oceanic moisture sources where polar precipitation originates. Measurements of delta O-17 and "O-17 excess" (Delta O-17) are also of interest because of their potential to provide information complementary to d. Such measurements are challenging because of the greater precision required, particularly for Delta O-17. Here, high-precision measurements are reported for delta O-17, delta O-18, and delta D on a new ice core from the South Pole, using a continuous-flow measurement system coupled to two cavity ring-down laser spectroscopy instruments. Replicate measurements show that at 0.5 cm resolution, external precision is similar to 0.2 parts per thousand for delta O-17 and delta O-18, and similar to 1 parts per thousand for delta D. For Delta O-17, achieving external precision of <0.01 parts per thousand requires depth averages of similar to 50 cm. The resulting similar to 54,000-year record of the complete oxygen and hydrogen isotope ratios from the South Pole ice core is discussed. The time series of Delta O-17 variations from the South Pole shows significant millennial-scale variability, and is correlated with the logarithmic formulation of deuterium excess (d ( ln )), but not the traditional linear formulation (d).