NOAA/WDS Paleoclimatology - Wahoo Lake, Alaska 11,500 Year Physical Properties and Isotope Data

Despite recent progress in understanding high-latitude climate variability, paleoclimate records are scarce from the Alaskan Arctic. We conducted isotopic and sediment analyses at Wahoo Lake to infer Holocene climate variability in northeastern Alaska. Water d18O and dD values from the lake and its inlet/outlet streams suggest that winter precipitation dominates modern water inputs and that evaporation has limited influence on the lake's hydrological budget. The isotopic composition of Pisidium exhibits marked variations during the past 11,500 years, with d18O ranging between -18.7 and -16.2 per mil and d13C between -7.1 and -2.3 per mil (Vienna Pee Dee Belemnite (VPDB)). Elevated d18O and sediment composition from 11.5 to 8.9 kcal. BP suggest evaporative 18O enrichment and arid conditions. Rising lake levels are evidenced by the disappearance of Pisidium and a transition to low-carbonate gyttja ca. 6.3 kcal. BP and by the onset of sediment deposition on an adjacent shelf by 5.3 kcal. BP. These changes coincided with enhanced effective moisture in interior and southern Alaska as inferred from lake-level records and may be related to broad-scale atmospheric circulation changes. In the shelf sediments, carbonate abundance increases markedly at 3.5 kcal. BP, and d18O increases from -18.0 to -16.5 per mil at 2.1 kcal. BP, possibly resulting from increased temperature and/or summer precipitation. After 2.1 kcal. BP, d18O fluctuates with an overall decreasing trend to -17.2 per mil at 0.9 kcal. BP. Late-Holocene variations in our d18O record display coherent patterns with regional glacier fluctuations at centennial to millennial scales, suggesting that d18O minima were related to a combination of low temperatures and enhanced winter snowfall. Holocene variations in organic matter abundance at Wahoo Lake also show broad similarities to total solar irradiance, implying that suborbital solar variability played a role in modulating regional climate and aquatic productivity.