Reply to: Limitations of ice cores in reconstructing temperature seasonality

replying to: T. Laepple et al. Nature https://doi.org/10.1038/s41586-024-08181-7 (2025).

Reconstruction of seasonal temperatures from ice cores requires consideration of multiple factors affecting signal preservation and generating uncertainty. The West Antarctic Ice Sheet (WAIS) Divide ice core (WDC) preserves a large range of seasonal water-isotope amplitudes, which partly arises from inconsistency of preservation rather than variability of the corresponding seasonal temperature amplitudes. Here we consider whether such incomplete preservation affects the results of Jones et al.¹ (hereafter J23), which exclusively concerned millennial-scale temperature trends. By exploiting variability inherent in the WDC data, we demonstrate that signal preservation has only a small effect on our results for both summer and winter trends, well within uncertainty ranges reported in J23, unless certain systematic biases exist. We also consider a scenario in which uncertainty on the diffusion correction could be consistent with constant seasonal water-isotope amplitudes across the entire Holocene. This scenario corresponds to seasonal temperature changes that also lie well within the uncertainty ranges of J23. Nonetheless, we emphasize the considerable potential for systematic biases in seasonal temperature reconstructions and encourage further work on this topic.