Diatom record of holocene moisture variability in the San Bernardino Mountains, California, USA.

Abstract

Lower Bear Lake, in the San Bernardino Mountains, contains a Holocene paleohydrology record for southern California. The diatom and sediment geochemistry record indicates that the region experienced a wet Early Holocene followed by a gradual decrease in precipitation, which was punctuated by four strong and five weak pluvial episodes. The Lower Bear Lake record is compared with that of Silver Lake, a Mojave River terminal lake with headwaters in the San Bernardino Mountains, which exhibited several pluvial events at roughly the same time. The comparison is extended to records in relative proximity to Bear Lake (Dry Lake, Lake Elsinore, and San Joaquin marsh) and to two lakes with headwaters in the Sierra Nevada (Tulare Lake and Owens Lake). All exhibit a wet Early and early Middle Holocene wet interval and gradual drying through the remainder of the Holocene but differ in the expression of the pluvial episodes observed at Lower Bear Lake. The pluvial episodes are likely the result of changes in the storm track that affects the frequency and magnitude of winter storms in the area. These episodes are controlled by complex oceanic and atmospheric interactions and may be the result of the synchronous interaction of several teleconnections.