Southern Baffin Island mean annual precipitation isotopes modulated by summer and autumn moisture source changes during the past 5800 years

Paleo water isotope records can elucidate how the Arctic water cycle responded to past climate changes. We analyze the hydrogen isotope composition (delta H-2) of plant-derived n-alkanoic acids (waxes) from Lake Qaupat, Baffin Island, Nunavut, Canada, to assess moisture sources and seasonality during the past 5.8 ka. We compare this record to a sedimentary ancient DNA (sedaDNA)-inferred vascular plant record from the same lake, aiming to overcome the uncertainty of plant community impacts on leaf waxes. As the sedaDNA record reveals a stable plant community after the colonization of Betula sp. at 6.1 ka, we interpret plant wax delta H-2 values to reflect climate, specifically mean annual precipitation delta H-2. However, the distributions of n-alkanoic acid homologs suggest that aquatic mosses, which are not represented in the sedaDNA record, may become more abundant towards the present. Therefore, we cannot exclude the possibility that changes in the plant community cause changes in the plant wax delta H-2 record, particularly long-chain waxes, which become less abundant through this record. We find that Lake Qaupat mid-chain plant wax delta H-2 is enriched coincident with high Labrador Sea summer surface temperature, which suggests that local moisture sources in summer and early autumn have the greatest impact on precipitation isotopes in this region.