How precipitation intermittency sets an optimal sampling distance for temperature reconstructions from Antarctic ice cores

Abstract

Abstract. Many palaeoclimate proxies share one challenging property: they\nare not only driven by the climatic variable of interest, e.g. temperature, but\nthey are also influenced by secondary effects which cause, among other things, increased variability, frequently termed noise. Noise in individual proxy records can be reduced by averaging the records, but the effectiveness of this\napproach depends on the correlation of the noise between the records and\ntherefore on the spatial scales of the noise-generating processes. Here, we\nreview and apply this concept in the context of Antarctic ice-core isotope\nrecords to determine which core locations are best suited to reconstruct\nlocal- to regional-scale temperatures. Using data from a past-millennium climate model simulation equipped with stable isotope diagnostics we intriguingly find that even for a local temperature reconstruction the optimal sampling strategy is to combine a local ice core with a more distant core ∼\u2009500–1000\u2009km\naway. A similarly large distance between cores is also optimal for\nreconstructions that average more than two isotope records. We show that these findings result from the interplay of the two spatial scales of the correlation structures associated with the temperature field and with the noise generated by precipitation intermittency. Our study helps to maximize the usability of existing Antarctic ice cores and to optimally plan future drilling campaigns. It also broadens our knowledge of the processes that shape the isotopic record and their typical correlation scales. Finally, many palaeoclimate reconstruction\nefforts face the similar challenge of spatially correlated noise, and our\npresented method could directly assist further studies in also determining\noptimal sampling strategies for these problems.\n