Coastal Wetland Sedimentation and Climate

Southern California is subjected to a unique climate.  Although typical conditions call for a Mediterranean climate, with wet winters and dry summers, the region can be significantly impacted by extreme climatic events and cycles such as the El Niño Southern Oscillation (ENSO).  With future climate change these extreme events are predicted to become more frequent and more intense.  In the end, these extremes may have more of an impact than "fair-weather" conditions.

 

Sedimentation and ENSO at Upper Newport Bay

This plot depicts interval-specific sedimentation rates (black line) from a mudflat core in Upper Newport Bay versus the multivariate ENSO index (blue and red).  When the ENSO index is positive, these are times of El Niño (red), and southern California typically experiences increased storminess during the winter.  Notice how the sedimentation rate tends to peak in correspondence with positive ENSO periods.  The increased rainfall brought on by ENSO, increases the sediment flux to the bay, resulting in increases in sediment accumulating along the mudflat.  During La Niña periods (blue), storms are less frequent and less intense, reducing sediment fluxes, and sediment accumulation along the mudflats.  One noticeable deviation from this trend occurs in 201-2012, where a peak in sediment accumulation corresponds to a La Niña period.  This was a year that southern California experienced strong winter storms as a result of a different climate phenomenon referred to as atmospheric rivers.  A similar set of conditions recently occurred in the winter of 2016-2017.  These data highlight that strong control climate has on the delivery of sediment to the wetlands.