Late Holocene (3.0-2.6 ka) enhancement of ocean-terrestrial teleconnections in California, Nevada, and coastal Oregon

Abstract:

Proxy sea surface temperature (SST) records off Baja and Alta California display a consistent increase occurring between 4 and 3 ka that argues for a strengthening of positive Pacific Decadal Oscillation (PDO) conditions. By 3 ka, warmer SSTs in the northeast Pacific appear to have stimulated an intensification of the North Pacific Gyre Oscillation (NPGO), as evidenced by a stepwise increase in coastal upwelling at ~2.9 ka documented in numerous offshore records along the California coast. The tight coupling of PDO, which drives SST variability and wet winters in the eastern North Pacific and its margins, and the NPGO, which results in variations of sea surface salinity, driving upwelling intensity along the California coast, appears to have been developed at this time. A census of 23 precipitation records from California, Nevada, and coastal Oregon reveals that regional precipitation patterns, which contrast a dry (wet) northwest vs. a wet (dry) southwest region, were enhanced between ~2.8 and 2.5 ka, arguing for the development of the PDO Precipitation Dipole in northwestern North America. In a number of records this transition was preceded by a pluvial event lasting at least 200 yrs. The apparent intensification of coupled PDO and NPGO cycles between ~2.8 and 2.5 ka was likely driven by insolation change and possibly reflects an intensification in the circulation of the North Pacific (subarctic) Gyre, however, the ultimate cause of this seemingly abrupt transition in linked ocean-atmosphere dynamics remains unclear