A 1300 Year Sub-Decadally Resolved Hydrologic Record from the Coastal Southwestern United States (Crystal Lake, CA)

Abstract:

This study presents a 1300 year sub-decadally resolved record of hydrologic variability from coastal southwestern United States (Crystal Lake, CA). Crystal Lake is a small (0.02 km²), alpine landslide dammed lake in the Angeles National Forest of the San Gabriel Mountains. The hydrologically closed lake is the only permanent, freshwater lake in the range; its catchment is small (0.77 km²). In May 2014, lake depth measured 5.5 m, however the spillover point in the southeastern end of the lake indicates a max depth of ~50 m. Two Livingston piston cores were taken in May 2014, 15 m apart in the lake’s depocenter. Magnetic susceptibility, LOI 550 °C and 950 °C, and grain size were measured at 1 cm contiguous intervals; C:N ratios and C and N isotopic analyses were measured every 2 cm. In addition, representative allochthonous and autochthonous vegetation were collected within the drainage basin for δ¹³C_org values. An age model was generated using Bacon v2.2, based on 11 AMS ¹⁴C dates of discrete organic matter (i.e. charcoal or wood). Age control for the past 200 years is based on correlation to Rothenberg et al. (2010) core ages. Initial results suggest a history of event sedimentation (large storms) superimposed on multi-decadal to centennial hydrologic changes (wet vs. dry periods) such as the Little Ice Age and the Medieval Climate Anomaly. Additionally, the Crystal Lake record is compared to preexisting regional records to further explore the record’s spatial coherence. Mechanisms driving these hydrologic shifts are explored.