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.
Bibliographical noteFunding Information:
Work at June Lake was permitted through the Inyo National Forest (USFS). We thank the Overcash Fund for Field Research and alumni donors to the UK Field Geology Fund for field work support. Partial funding was also provided by Lawrence Livermore National Laboratory (USA) grant 17-ERD-052 to SZ; this is LLNL-JRNL-764279 . We thank David Osleger for sharing data for comparison from Lake Tahoe. We are grateful to John and Mickey Frederickson at the June Lake Marina for generously allowing us to use their facilities and equipment. We also thank UK students and staff, especially J. Lucas and J. Munizzi, for field and lab assistance. We appreciate the staff of LacCore for their assistance with core preparation and sampling. We are grateful to two anonymous reviewers whose comments improved the manuscript.
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- North America
- Organic geochemistry
- Stable isotopes