SIGNIFICANT CHANGES IN HOLOCENE HYDROCLIMATIC VARIABILITY RECORDED IN BARLEY LAKE SEDIMENTS, CALIFORNIA (NORTHERN CALIFORNIA COAST RANGE)

It is now evident that the Holocene in the western United States was characterized by high amplitude, multi-frequency hydroclimatic changes with significant spatiotemporal variability. Although diminutive by comparison to the Last Glacial Period, it is important to understand Holocene climatic variability, as it is relevant to modern society and their understanding of past baseline variability and future climatic adaptation and mitigation. Arid environments, such as the western United States, face a particular challenge located at the nexus of population growth, water resources, and agricultural sustainability – the latter being especially important for California. Here, we present various physical, chemical, and biological sediment core data from Barley Lake, CA (BLRC17-2, 750 cm length), located in the northern California Coast Range, constrained by 29 x AMS ¹⁴C ages. Barley Lake’s shift from a deep late-Glacial lake to a shallow Holocene lake characterizes the end of the Younger Dryas. Although uniformly shallower than the late-Glacial lake, the Holocene lake is characterized by dynamic changes in hydrology and inferred lake depth. A progressive increase in water depth occurs between 11.7 and 8.0 ka before a rapid shoaling at 7.9 ka, lasting until ~7.2 ka. Lake depth begins to increase again at 7.2 ka, reaching an apparent Holocene maximum(?) from 6.6 to 6.4 ka. Lake depth decreases abruptly at 6.3 ka and remains shallow until ~5.1 ka. A slight increase in lake depth occurs ca. 5.0 ka before declining and remaining variably shallow between 4.9 and 2.6 ka. Closely spaced dates indicate a sediment hiatus resulting from an extreme low stand, perhaps lake desiccation, between 2.0 and 0.4 ka before lake depth increases again during the Little Ice Age. The hiatus may correspond to the most driest part of the Late Holocene dry period (e.g., Mensing et al., 2023). Future work will examine these inferred changes in lake hydrology in the context of climatic drivers such as insolation, sea surface temperatures, and ocean-atmosphere dynamics (e.g., El Niño-Southern Oscillation).