Climatic information archived in ice cores: impact of intermittency and diffusion on the recorded isotopic signal in Antarctica

• Main Authors: Casado, Mathieu, Münch, Thomas, Laepple, Thomas
• Format: Text
• Language: English
• Published: 2019
• Subjects: Antarc*; Antarctica; ice core
• Online Access: https://doi.org/10.5194/cp-2019-134; https://cp.copernicus.org/preprints/cp-2019-134/

The isotopic signal ( δ 18 O and δD ) imprinted in ice cores from Antarctica is not solely generated by the temperature sensitivity of the isotopic composition of precipitation but also contains the signature of the intermittency of precipitation patterns as well as of post-deposition processes occurring at the surface and in the firn. This leads to a proxy signal recorded by the ice cores that may not be representative of the local climatic variations. Due to precipitation intermittency, the ice cores only record brief snapshots of the climatic conditions, resulting in aliasing of the climatic signal, and thus a large amount of noise which reduces the minimum temporal resolution at which a meaningful signal can be retrieved. The analyses are further complicated by isotopic diffusion which acts as a low pass filter that dampens any high frequency changes. Here, we use reanalysis data (ERA-Interim) combined with satellite products of accumulation to evaluate the spatial distribution of the transfer function that describes the formation of the isotopic signal across Antarctica. The minimum time scales at which the signal-to-noise ratio exceeds unity range from less than a year at the coast to a thousand years further inland. Based on solely physical processes, we were thus able to define a lower bound for the time scales at which climate variability can be reconstructed from ice core water isotopic compositions.