Articles | Volume 12, issue 7
Clim. Past, 12, 1565–1581, 2016
Clim. Past, 12, 1565–1581, 2016

Research article 22 Jul 2016

Research article | 22 Jul 2016

Regional climate signal vs. local noise: a two-dimensional view of water isotopes in Antarctic firn at Kohnen Station, Dronning Maud Land

Thomas Münch1,2, Sepp Kipfstuhl3, Johannes Freitag3, Hanno Meyer1, and Thomas Laepple1 Thomas Münch et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A43, 14473 Potsdam, Germany
  • 2Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
  • 3Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Alten Hafen 26, 27568 Bremerhaven, Germany

Abstract. In low-accumulation regions, the reliability of δ18O-derived temperature signals from ice cores within the Holocene is unclear, primarily due to the small climate changes relative to the intrinsic noise of the isotopic signal. In order to learn about the representativity of single ice cores and to optimise future ice-core-based climate reconstructions, we studied the stable-water isotope composition of firn at Kohnen Station, Dronning Maud Land, Antarctica. Analysing δ18O in two 50 m long snow trenches allowed us to create an unprecedented, two-dimensional image characterising the isotopic variations from the centimetre to the 100-metre scale. Our results show seasonal layering of the isotopic composition but also high horizontal isotopic variability caused by local stratigraphic noise. Based on the horizontal and vertical structure of the isotopic variations, we derive a statistical noise model which successfully explains the trench data. The model further allows one to determine an upper bound for the reliability of climate reconstructions conducted in our study region at seasonal to annual resolution, depending on the number and the spacing of the cores taken.

Short summary
Ice-core oxygen isotope ratios are a key climate archive to infer past temperatures, an interpretation however complicated by non-climatic noise. Based on 50 m firn trenches, we present for the first time a two-dimensional view (vertical × horizontal) of how oxygen isotopes are stored in Antarctic firn. A statistical noise model allows inferences for the validity of ice coring efforts to reconstruct past temperatures, highlighting the need of replicate cores for Holocene climate reconstructions.