Greenland Ice Core Isotope Variability Strongly Influenced by Systematic Changes in Depositional Noise

Abstract

Stable water isotopes from ice cores are a unique proxy for reconstructing polar climate variability. Their interpretation is, however, challenging due to the impact of depositional noise. Here, we analyze the centennial‐ to millennial‐scale isotope variability of the Greenland ice cores NGRIP, GRIP, and GISP2 to investigate how their coherent signal and local noise have evolved over the last 100,000 years. We show that the noise systematically depends on the climate state, with higher levels under colder temperatures and lower accumulation rates. Most of the noise originates from local stratigraphic disturbances, while additional noise variability only emerges in the Greenland stadials. The remaining climate signal variability is higher in the last glacial period compared to the Holocene, but does not systematically differ between stadials and interstadials. We show that, by considering systematic changes of noise, it is possible to achieve more accurate estimates of past climate variability.