High-frequency climate oscillations in the Holocene from a coastal-dome ice core in east central Greenland

Abstract. An ice core drilled on the Renland Ice Cap in east-central Greenland contains a continuous climate record dating through the last glacial period. The Renland record is valuable because the coastal environment is more likely to reflect regional sea surface conditions, compared to inland Greenland ice cores that capture synoptic variability. Here we present the δ18O water isotope record for the Holocene, in which decadal-scale climate information is retained for the last 8 ka, and the annual water isotope signal is preserved throughout the last 2.6 ka. To investigate regional climate information preserved in the water isotope record, we apply spectral analysis techniques to a 300-year moving window to determine the mean strength of varying frequency bands through time. The strength of interannual frequency bands decays rapidly, but we find that the mean 15–20 year δ18O variability exhibits a millennial-scale cycle in line with the well-known Bond Cycle. Comparison to other North Atlantic proxy records suggests that the 15–20 year variability may reflect fluctuating sea ice conditions throughout the Holocene, driven by changes in the strength of the Atlantic Meridional Overturning Circulation. Additional analysis of the seasonal signal over the last 2.6 ka reveals that the winter δ18O signal has experienced a decreasing trend, while the summer signal has predominantly remained stable. The winter trend likely corresponds to an increase in Arctic sea ice cover, driven by a decrease in total annual insolation. In the context of anthropogenic climate change, the winter trend may have important implications for feedback processes as sea ice retreats in the Arctic.