Mid-Wisconsin sediment record from Baldwin Lake reveals hemispheric climate dynamics (Southern CA, USA)

Recently acquired cores from Baldwin Lake, Southern California, document the first regional, terrestrial-based evidence for glacial period millennial-to-orbital scale climate variability. Eight AMS 14C dates on a 14-m core from the lake's present day depocenter provide initial age control over the interval from 20,000 to 48,000 years before present (BP). A linear age model extends the record to a minimum age of 65,000 years BP. A combination of lithologic description and one cm contiguous sedimentological analyses indicates significant changes in the dominant type of depositional environment over the length of the record at millennial-to-orbital time scales. As a first-order interpretation, the dominant sedimentary environments alternate between permanent and ephemeral lake systems. Orbital-scale forcing includes long-term winter-summer insolation variability and its modulation of winter storm tracks and the North American monsoon, respectively. Millennial-scale variability is attributed to extra-tropical, ocean–atmosphere dynamics akin to historical interdecadal Pacific climate variability. In addition, there is notable correspondence to the independently dated Greenland Ice Core record (GISP 2) at millennial-to-orbital time scales suggesting that Baldwin Lake contains, in addition to its local/regional record, a hemispheric record of climate change — similar to Owens, Pyramid, and Summer Lake of central and northwestern North America. An initial comparison to GISP2 δ18O(ice) indicates that North Atlantic interstadials correlate to permanent lake environments in coastal southwestern North America. These results present a notable conflict with the proposed “super-ENSO” phenomenon in the western tropical Pacific. These results also highlight the necessity for acquiring additional high-resolution glacial period records for resolving questions of spatial–temporal phasing of late-Quaternary climates.