NOAA/WDS Paleoclimatology - Lake Elsinore, California 32-10ky Physical Properties and Pollen Data

Continuous, sub-centennially resolved, paleo terrestrial records are rare from arid environments such as the Pacific south-west United States. Here, we present a multi-decadal to centennial resolution sediment core (Lake Elsinore, CA) to reconstruct late Wisconsin pluvials, droughts and vegetation. In general, the late Wisconsin is characterized by a wetter and colder climate than during the Holocene. Specifically, conditions between 32.3 and 24.9k cal a BP are characterized by large-amplitude hydrologic and ecologic variability. Highlighting this period is a ~2000-year glacial mega-drought (27.6-25.7k cal a BP) during which the lake shallowed (3.2-4.5m depth). This period is approximately coeval with a Lake Manix regression and an increase in xeric vegetation in the San Bernardino Mountains (Baldwin Lake). The Local Last Glacial Maximum (LLGM) is bracketed between 23.3 and 19.7k cal a BP - a ~3000-year interval characterized by reduced run-off (relative to the glacial), colder conditions and vegetative stability. Maximum sustained wetness follows the LLGM, beginning at 19.7 and peaking by 14.4k cal a BP. A two-step decrease in runoff characterizes the Lateglacial to Holocene transition; however, the vegetation change is more complex, particularly at the beginning of the Younger Dryas chronozone. By 12.6-12.4k cal a BP, the climate achieved near Holocene conditions.

美国西南部太平洋沿岸等干旱环境中，连续且具备亚百年分辨率的古陆地记录十分匮乏。本文基于加利福尼亚州埃尔西诺湖的沉积岩芯，构建了数十年至百年分辨率的沉积序列，用以重建威斯康星冰期晚期的古多雨期、干旱事件与植被演化历史。总体而言，威斯康星冰期晚期的气候特征为较全新世更为湿冷。具体而言，32.3~24.9千校准距今年（cal a BP）时段的水文与生态波动幅度极大，其中27.6~25.7千cal a BP的持续约2000年的冰期巨型干旱事件尤为显著，该时段内湖泊水深仅3.2~4.5米。此时期大致与马尼克斯湖的湖退过程以及圣贝纳迪诺山脉鲍德温湖区的旱生植被扩张同期。本地末次冰盛期（LLGM）介于23.3~19.7千cal a BP之间，这一约3000年的时段以径流量减少、气候寒冷且植被稳定为特征。冰盛期过后出现持续时间最长的湿润期，始于19.7千cal a BP，并于14.4千cal a BP达到峰值。晚冰期向全新世的过渡以径流量的两步式下降为特征，但植被变化更为复杂，尤以新仙女木时段初期为甚。至12.6~12.4千cal a BP时，气候已接近全新世平均状态。