Using Holocene sediments from North Yolla Bolly Lake in the Northern Coast Range (CA) to investigate the California precipitation dipole.

Where California receives its precipitation is as important, if not more, than how much precipitation it receives. Key to the "where and how much" issue is the California precipitation dipole (Dettinger et al., 1998; Wise, 2010). This dipole defines an approximate boundary of opposite precipitation signals - wetter north/drier south and vice versa. Based on a 500-yr tree ring study, the average position of the dipole sits at 40° N latitude (Wise, 2016). Over 500 years, however, the dipole has varied between 35° and 44° N. To extend the dipole's record beyond 500 years, we are collecting lake sediment cores along a north-south CA transect. Here, we present initial results from North Yolla Bolly Lake (40° N), located in the Northern Coast Range. Six sediment cores were collected in July 2018 from various depths. Based on a sticky, grey basal clay, it is likely we collected the complete Holocene and into the late Glacial. The Holocene sediments consist of variegated brown, organic-rich muds with occasional laminae. High resolution radiocarbon dating of discrete organic materials will provide age control. A variety of physical, chemical, and biological analyses will be used to infer past changes in moisture. Results will be compared to existing sites north and south of North Yolla Bolly Lake, with a specific focus on the Little Ice Age, the Medieval Climatic Anomaly, and the Roman Warm Period.