GLACIAL TO HOLOCENE CALIFORNIA CLIMATE INFERRED FROM TWO MULTI-PROXY SPELEOTHEM RECORDS

Speleothem records from western North America have provided valuable insights into variations in precipitation and moisture transport to this water sensitive region during the last glacial period and deglaciation. Here we present multi-proxy speleothem records from two California caves, Lake Shasta Caverns (LSC) in northern California, and White Moon Cave (WMC) in the Santa Cruz Mountains on the central California coast, that document hydroclimatic changes that are synchronous with regional and global climate events from the last glacial period to the Holocene. Speleothem LSC3 grew from ~36 to 14 ka, through the MIS 3/2 transition and the beginning of the last deglaciation. Speleothem WMC1 grew from ~6.9 to 8.6 ka and provides a high-resolution record of the response of coastal California climate to the 8.2 kyr event.

Increased δ¹⁸O and δ¹³C in LSC3 and slower stalagmite growth during MIS 2 suggest increased subtropical moisture but dry conditions in Northern California. The δ¹³C record displays distinct millennial-scale oscillations during MIS 3, suggesting drier conditions also occurred during interstadials associated with Dansgaard-Oeschger cycles. The LSC3 δ¹⁸O record documents changes synchronous with δ¹⁸O variations in the Fort Stanton stalagmite in New Mexico, though sometimes in phase (e.g. during Heinrich Stadial 1; HS1) and sometimes anti-phased (e.g. during the Bölling). Likewise, the LSC3 δ¹³C record suggests a transition from wet to drier conditions during HS1 in contrast to more southerly records that indicate wetter conditions later in HS1. The early Holocene WMC1 record documents high-frequency, large amplitude variations in δ¹³C and pulsed increases in P concentration during the 8.2 kyr event. These changes, coupled with overall lower Mg/Ca, suggest that the 8.2 kyr event was characterized by increased frequency or intensity of storms on the California coast. This would be consistent with an intensification of the Pacific winter storm track in response to freshwater input into the North Atlantic due to the drainage of Lake Agassiz. Both the glacial/deglacial LSC3 record, and the Holocene WMC1 record point to robust but variable teleconnections and link California climate with distally forced climate changes on long (glacial/interglacial) and abrupt (DO cycles, 8.2 kyr event) timescales.