Early Holocene Atmospheric Circulation Changes Over Northern Europe Based on Isotopic and Biomarker Evidence From Kola Peninsula

Rapid Arctic warming this century will likely cause major water cycle and atmospheric circulation changes, including weakening mid-latitude westerly winds and more persistent summer high pressures over Fennoscandia. These conditions can cause drought in northern Europe and extreme rainfall in the Mediterranean region. Uncertainties in the spatiotemporal patterns of these predictions can be partially addressed with records of past climate response to rapid change. The early Holocene collapse of the Northern Hemisphere ice sheets provides a natural experiment to evaluate the climate response to rapid changes in boundary conditions. We analyzed lipid biomarker distributions and hydrogen isotope (δ²H) values from Lake Imandra, Kola Peninsula, to infer Holocene summer temperature and summer precipitation δ²H values. Sensitivity tests of a lake model suggest summer precipitation δ²H values are the main mechanism influencing Lake Imandra δ²H values. Summer precipitation isotope values exhibited a nearly 20‰ ²H-depletion between 8.6 and 8.0 ka, with ²H -enriched values before 8.6 ka and ²H -depleted values 8.0 ka to present. Maximum warmth occurred from 8.5 to 7.0 ka. Climate model experiments suggest that the early Holocene Laurentide Ice Sheet collapse caused a westward shift of the Fennoscandian summer high-pressure center. This caused a decrease in the proportion of local, ²H-enriched precipitation falling throughout Fennoscandia and an increase in far-traveled, ²H-depleted precipitation from the mid-latitudes, circulation that persisted throughout the Holocene. These results illustrate the sensitivity of climate in Fennoscandia and show that circulation regime shifts can occur in response to changes in boundary conditions far upwind.