THE INFLUENCE OF THE EASTERN PACIFIC OCEAN ON THE HOLOCENE PALEOCLIMATE RECORDS OF THREE WESTERN MIDDLE AND HIGH ELEVATION LAKES AND SAN FRANCISCO BAY
Medicine Lake (2,036 masl) in northwestern California is presently a closed-basin lake that receives most of its water from snowpack. Comparison with the multi-proxy record from ODP Site 1019 off northern California demonstrates a significant connection between SST and the annual amount and distribution of precipitation which is reflected in lake level throughout the Holocene. Swamp Lake (1,554 masl) is a small, middle elevation lake in the northwestern corner of Yosemite National Park. Much of the ~19,000 year record is varved, providing a high-resolution record. Multiple proxies record changes in lake level and productivity. Both records suggest suppression of ENSO and possibly stronger or more frequent negative PDO intervals during the middle Holocene. Higher ENSO/positive PDO frequency in the late Holocene is suggested by higher lake levels and higher productivity.
Located in the Ruby Mountains in northeastern Nevada, Favre Lake (3,029 masl) is affected by a more complicated set of atmospheric conditions than either of the previously discussed lakes. Preliminary results of multi-proxy analyses show similarities to middle and late Holocene lacustrine environmental records of both the Pacific and Rocky Mountain regions.
San Francisco Bay (SFB) receives fresh water from more than 40% of California, and therefore provides a record of climate variability over much of the state. Marsh records from the northern bay correspond well with other records of shorter duration allowing synthesis of late Holocene precipitation records. The Medieval Climate Anomaly is represented by decreased freshwater flow into SFB due to lower SST and decreased transportation of moisture eastward into California. Increased ENSO/positive PDO during the Little Ice Age resulted in greater moisture transport and increased freshwater flow into SFB.