CORRELATING LATE GLACIAL AND HOLOCENE MARINE AND LACUSTRINE CLIMATE RECORDS IN NORTHERN CALIFORNIA

Long-distance connections between marine and terrestrial environments on the California margin are affected by both latitude and elevation. In this study, the late glacial and Holocene history of the California Current (CC), derived from a marine core, is compared with two lake records. The 16,000-year-long marine record (Site 1019) is based on the analysis of diatoms, pollen, alkenones, sediment geochemistry, and physical properties. The 19,000-year-long Swamp Lake (SL; 1,518 m) record, includes pollen, diatoms, biogenic silica (BSi), loss-on-ignition (LOI), and magnetic susceptibility. The 11,400-year-long Medicine Lake (ML; 2,036 m) record, located in northeastern California, is based on diatoms, pollen, sediment geochemistry, and physical properties.

The marine and SL records indicate cooler temperatures and decreased productivity during the transition from the Bølling-Allerød to the Younger Dryas (YD). Early Holocene climate was characterized by a transition from warmer and wetter to cooler and drier conditions along the coast and in inland areas, warm winter sea surface temperatures (SST) and a CC of moderate strength. The BSi levels in SL increased during this time, as does the abundance of oligotrophic planktonic taxa. Clastic input decreased in both lakes during this period, suggesting increased vegetation in the watershed. The warmest temperatures were reached toward the end of the early Holocene at SL. At ML, conditions were relatively stable throughout the early Holocene.

Middle Holocene climate was characterized by weaker, less regular El Niño events, and more sustained La Niña-like conditions resulting in lower coastal SST and drier conditions inland. A stronger CC thermal gradient led to increased seasonal coastal upwelling and fog along the coast during the latter half of this interval. At SL, biogenic silica values increased, and pollen from both lakes suggests an increase in effective moisture.

Late Holocene climate was distinguished by increased winter precipitation and enhanced ENSO cycles. The marine record suggests warmer winter SST and a stronger seasonal gradient. The pollen records at both lakes show increased effective moisture. However, the productivity in ML decreased to levels recorded in the earliest Holocene, while productivity in SL remained at middle Holocene values.