Synchronous Early Holocene Summer Hydroclimate Variability Throughout the Eastern North American Arctic Driven by Changes in Poleward Moisture Transport

Arctic precipitation is predicted to increase this century, with dramatic consequences for the Arctic system. High-latitude hydrological intensification has been attributed to enhanced local evaporation and greater poleward moisture transport. Yet, observations remain spatiotemporally limited, hampering determination of the mechanisms causing these changes. We shed light on these mechanisms using sub-centennial-resolution multi-proxy lake sediment records spanning 9.5 to 7.0 ka at Sikuiui Lake on western Greenland and 12.0 to 7.0 ka at Lake CF8 on eastern Baffin Island. We study lakes that have short (<3 month) lake water residence times, in which aquatic plant leaf wax hydrogen isotopes reflect summer precipitation isotopes.

Changes in branched GDGT-inferred summer temperature and aquatic plant leaf wax-inferred summer precipitation δ²H were synchronous on the eastern and western margins of Baffin Bay, suggesting that large-scale atmospheric reorganizations occurred in response to changing temperature. Rapid warming events punctuated the end of cool intervals in these records at 10.9 ka, 9.6 ka, 9.2 ka, and 8.1 ka. Rayleigh distillation during long-distance poleward moisture transport causes ²H-depleted summer precipitation at these sites, whereas moisture evaporated from local sources remains ²H-enriched. Thus, moisture transport history overwhelms local condensation temperature as the main mechanism influencing summer precipitation isotopes at these sites. We observe ²H-depleted summer precipitation coincident with warm summers on both margins of Baffin Bay, suggesting that poleward moisture transport strengthened during warm Arctic summers. Furthermore, we quantify summer relative humidity at each site using paired terrestrial and aquatic leaf wax δ²H records. These records provide independent support for predictions of increased poleward moisture transport causing wetter Arctic summers in step with global ocean and atmosphere warming.