Seasonal precipitation variability on Svalbard inferred from Holocene sedimentary leaf wax δ²H

Svalbard spans large climate gradients, associated with atmospheric circulation patterns and variations in ocean heat content and sea ice cover. Future precipitation increases are projected to peak in the northeast and to mainly occur in winter, but uncertainties underscore the need for reconstructions of long-term spatial and temporal variations in precipitation amounts and seasonality. We use lipid biomarkers from four sedimentary lake records along a climatic gradient from western to northeastern Svalbard to reconstruct Holocene water cycle changes. We measured the leaf wax hydrogen isotopic composition of long-chain (terrestrial) and mid-chain (aquatic) n-alkanoic acids, reflecting delta H-2 of precipitation (delta H-2(precip)) and lake water (delta H-2(lake)), respectively. delta H-2(precip) values mainly reflect summer precipitation delta H-2 and evapotranspiration, whereas delta H-2(lake) values can reflect various precipitation seasonality due to varying lake hydrology. For one lake, we used the difference between delta H-2(precip) and delta H-2(lake) (epsilon(precip-lake)) to infer summer evapotranspiration changes. Relatively H-2-enriched delta H-2(precip) values and higher epsilon(precip-lake) in the Early and Middle Holocene suggest warm summers with higher evapotranspiration, and/or more proximal summer moisture. After c. 6 cal. ka BP, H-2-depleted delta H-2(precip) values and lower epsilon(precip-lake) indicate summer cooling, less evapotranspiration, or more distally derived moisture. Early to Middle Holocene decrease in delta H-2(lake) values in two northern Spitsbergen lakes reflects an increase in the proportion of winter relative to summer precipitation, associated with regional warming and increased moisture supply, which may be due to increased distal moisture supply and/or reduced sea ice cover. Our northern Svalbard delta H-2(lake) records suggest great Late Holocene climate variability with periodic winter precipitation increases or decreases in summer precipitation inflow to the lakes. We find that Holocene summer precipitation delta H-2 values mainly follow changes in summer insolation and temperature, whereas the seasonal distribution of precipitation is sensitive to catchment hydrology, regional ocean surface conditions, and moisture source changes.