Collaborative Research: REU: Calibrating the Water Isotope Thermometer in Antarctica Using Abrupt Heinrich Event Signatures in the EDML Ice Core

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This project seeks to answer the question, "How cold was Antarctica during the last ice age?" This information will help to predict the magnitude of future warming in Antarctica due to human emissions of heat-trapping gases, with implications for the stability of Antarctic ice sheets and sea level in the next 50 to 100 years. The proposed method uses a new "gas thermometer" based on air trapped in snow and preserved as air bubbles in ice that can be recovered from ice cores. The new thermometer uses ratios of nitrogen and argon isotopes (an isotope of a given element has a different number of neutrons) from the air bubbles in the ice and has been used successfully in Greenland over the past two decades to show that Greenland temperatures during the last ice age were ~35 degrees Fahrenheit colder than at present. Antarctica is more challenging to study than Greenland, but recent improvements in the gas thermometer now make it practical to address Antarctica's temperature history and inform its future under human influence. This project will train graduate and undergraduate students in these methods.The classical method for obtaining past temperatures on polar ice sheets uses the isotopes of water (18O and 2H) and has been shown to suffer from biases, for example underestimating Greenland cooling in the Last Glacial Maximum by a factor of 2. This project seeks to calibrate the water-isotope thermometer in East Antarctica using the recently improved inert-gas thermometer based on isotopes of N2 and Ar. The project will use ice from a core from East Antarctica (Dronning Maud Land) in collaboration with European colleagues. Further, ice samples of the same age from a West Antarctic ice core will be measured as a benchmark. The project will also perform targeted measurements of methane and N2 isotopes along the length of the East Antarctic ice core, to better understand the climate history and firn evolution of the core. These measurements will enable a second, independent calibration of the water-isotope thermometer from the observed gas-age – ice-age difference along the East Antarctic core.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.