Continuous-Flow Analysis of δ17O, δ18O, and δD of H2O on an Ice Core from the South Pole

• Published in: Frontiers in Earth Science
• Main Authors: Steig, Eric J., Jones, Tyler R., Schauer, Andrew J., Kahle, Emma C., Morris, Valerie A., Vaughn, Bruce H., Davidge, Lindsey, White, James W.C.
• Other Authors: National Science Foundation
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2021
• Subjects: South Pole; ice core; South pole
• Online Access: http://dx.doi.org/10.3389/feart.2021.640292; https://www.frontiersin.org/articles/10.3389/feart.2021.640292/full

The δ D and δ 18 O 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 δ D and δ 18 O, is also commonly used to provide information about the oceanic moisture sources where polar precipitation originates. Measurements of δ 17 O and “ 17 O excess” (Δ 17 O) 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 Δ 17 O. Here, high-precision measurements are reported for δ 17 O, δ 18 O, and δ 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 ∼0.2‰ for δ 17 O and δ 18 O, and ∼1‰ for δ D. For Δ 17 O, achieving external precision of <0.01‰ requires depth averages of ∼50 cm. The resulting ∼54,000-year record of the complete oxygen and hydrogen isotope ratios from the South Pole ice core is discussed. The time series of Δ 17 O 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 ).