The Late Holocene Dry Period identified in the Northern Coast Range of California (Barley Lake): Evidence for a mean state change in the average position of the California precipitation dipole?
Abstract
California's economy is tightly coupled to water availability. Both too much and too little water present serious natural hazards. Climate model projections suggest an increase in the frequency of end member precipitation regimes for California (Swain et al., 2018). How CA prepares for its future can benefit from increased understanding of the patterns and reasons for past changes in hydroclimate. Of particular interest are past changes in the mean state of CA's climate that produce severe and sustained changes in water availability. Lake sediments provide a mechanism to look back into California's water history, with deeper time insight than possible from historical records or tree rings. There is growing evidence that a severe late Holocene, multi-centennial scale dry period characterized a large part of the American west, but also exhibited regional variations (Mensing et al., 2013). Understanding the spatiotemporal footprint of this previous dry period and its relevance to the future requires: 1) spatially strategic paleoarchive development, 2) high resolution age control, and 3) hydrologically sensitive indicators. Here, we present a new record from Barley Lake (CA), which extends the boundary of the Late Holocene Dry Period (LHDP) into a previously unreported area. Using a combination of physical and chemical data, coupled with high resolution radiocarbon age control, we find a prolonged hiatus in the sedimentation beginning ca. 2.3k cal yrs BP. Our best upper age limit for the termination of the LHDP is 0.39k cal yrs BP; however, pending radiocarbon dates are expected to constrain the upper limit with finer detail. The Pacific Northwest recorded higher precipitation during this general period (Steinman et al., 2012). Sites in the Pacific southwest US (e.g., Lake Elsinore, Lower Bear Lake, and Zaca Lake) all record a LHDP. Barley Lake is located at the 500-yr average latitude ( 40°N) of the CA precipitation dipole (Wise, 2016). Consequently, we can conclude that the position of the dipole was - on average - north of its 500-yr average latitude for multiple centuries during the late Holocene. Understanding the forcings that drive these sustained changes in the mean climate state of CA is critical if we are to project how future climate change will impact CA's water availability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP21B..07K
- Keywords:
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- 3335 North American Monsoon;
- ATMOSPHERIC PROCESSESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCESDE: 4914 Continental climate records;
- PALEOCEANOGRAPHYDE: 4938 Interhemispheric phasing;
- PALEOCEANOGRAPHY