Late Holocene hydroclimate changes in the eastern Sierra Nevada revealed by a 4600-year paleoproduction record from June Lake, CA

Abstract

Well-resolved lake sediment records are key to answering questions about past hydroclimate variability. These questions are particularly relevant in California (USA), where a recent drought stoked fears of water scarcity and caused significant agricultural and other economic losses in this populous state. To contextualize recent and past cycles of aridity, we utilized a Late Holocene lacustrine record from the eastern Sierra Nevada. This study presents geochemical and sedimentological data from June Lake, California to link changes in organic matter production to environmental variability over the last ∼4600 years. The earliest part of our record is characterized by relatively high productivity and wetter conditions than the modern lake system. This interval is followed by a series of distinct and prolonged droughts from ∼3600 to 1700 cal yr BP, an interval that includes the regionally pervasive Late Holocene Dry Period that is recorded in June Lake as enhanced carbonate precipitation and lower primary production. The interval from ∼1700 to 130 cal yr BP, encompassing both the Medieval Climate Anomaly and the Little Ice Age, is characterized by less-frequent droughts and generally high production in a wetter climate. In contrast, sediments of the past 130 years record an abrupt shift to drier conditions, indicated by marked declines in nearly all production indicators. This divergence is likely influenced by anthropogenic warming and suggests that the modern lake system is anomalous with respect to the longer record of change in the basin.