Antarctic accumulation seasonality

Arising from T. Laepple, M. Werner & G. Lohmann Nature 471, 91–94 (2011)10.1038/nature09825 ; Laepple et al. reply The resemblance of the orbitally filtered isotope signal from the past 340 kyr in Antarctic ice cores to Northern Hemisphere summer insolation intensity has been used to suggest that the northern hemisphere may drive orbital-scale global climate changes1. A recent Letter2 by Laepple et al. suggests that, contrary to this interpretation, this semblance may instead be explained by weighting the orbitally controlled Antarctic seasonal insolation cycle with a static (present-day) estimate of the seasonal cycle of accumulation. We suggest, however, that both time variability in accumulation seasonality and alternative stable seasonality can markedly alter the weighted insolation signal. This indicates that, if the last 340 kyr of Antarctic accumulation has not always looked like the estimate of precipitation and accumulation seasonality made by Laepple et al.2, this particular accumulation weighting explanation of the Antarctic orbital-scale isotopic signal might not be robust.