Holocene Hydroclimate in Coastal Southern California
Abstract
In Mediterranean climates, understanding winter storm variability (location, intensity, duration, and frequency) over multiple timescales is important for predicting water resource availability and the likelihood of natural hazard events. Existing Holocene hydroclimate records from coastal southwestern North America are limited, making it difficult to compare precipitation patterns in this region to inland regions. In the coastal southwest US, many ephemeral streams transport sediments only during or immediately following large precipitation events (storms). Therefore, fluvial-sourced paleoflood deposits in estuarine sediments may be good proxies for storm activity in the Holocene. Here we use diagnostic geochemical and grain size characteristics to differentiate marine-derived sand beds from fluvial-derived sand beds in Carpinteria Marsh, California. These fluvial-derived beds are interpreted to represent alluvial fans prograding into the marsh fringes during storm-induced flooding of the coastal plain. We find that flood deposition is especially frequent and associated with the greatest deposition of coarse sediment at 0.3-1 ka, 2.8-3.6 ka, 3.8-4.2 ka, and 4.9-5.3 ka. The Carpinteria record of floods does not consistently correlate with other proxies for ENSO, PDO, or SST, indicating increased winter precipitation associated with flooding in Carpinteria has multiple, complex origins. However, three wet periods recorded in Carpinteria are contemporaneous with other records of pluvials throughout the southwest North America, possibly indicating a regional increase in Atmospheric River (AR) frequency during these time periods. The Carpinteria sedimentary record also records periods of decreased flood-derived sedimentation, corresponding to records of persistent droughts throughout southwest North America. Estuarine sediments provide an additional archive of past hydroclimate that demonstrates centennial to millennial scale storm frequency and magnitude may be similar across a wide geographic span of southwestern North America.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP23D1513R
- 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