As expected, California is now in the throngs of the continual storm systems
that are the hallmark of El Niño in the southern portion of the California
Current region. Already, this El Niño is shaping up to be one of the top three
on record with some similarities to the 1997/98 El Niño-Southern Oscillation
(ENSO) event, but with some distinguishing differences as well, most notably in
the atmospheric dynamics (the Southern Oscillation part of the name) and in the
anomalous temperature patterns in the central Equatorial Pacific (e.g. is it a
Central Pacific El Niño/
El Niño Modoki?).
While the warmer than average sea surface temperatures off the coast are likely
now attributable to El Niño patterns, it is still somewhat difficult to
differentiate anomalous warming from the warm “blob” (or Pacific Warm Anomaly)
that produced similar patterns throughout the California Current region for the
last two or more years. For more detailed picture of the El Niño signature in
California, go to the CeNCOOS
El Niño page.
What is clear is that the atmospheric changes brought about by El Niño’s
arrival over the North Pacific have been strong enough to diminish the
influence of the “ridiculously resilient ridge” of high pressure that has been
sitting over California and preventing storm systems from alleviating the long
drought (see posts on the
California Weather Blog).
In this respect, El Niño is winning out
against the blob and leading to weather patterns that are not necessarily
conducive to phytoplankton growth and bloom development. Pseudo-nitzschia is
not entirely gone though, with cryptic populations resurging periodically,
particularly during calm periods following storms when light levels allow for
growth. It has not appeared to be prolonged enough or vigorous enough growth to
lead to accompanying high rates of domoic acid (DA, neurotoxin) production.
For this reason, there is hope that the residual pool of DA in the subsurface
and sediments that has been intoxicating crabs and devastating fishermen will
soon be depleted and/or mixed offshore. A bigger question now remains as to
what the spring will bring now that there is an established “seeding”
population of Pseudo-nitzschia that seems to be persisting off the coast.
Warm sea water anomalies and a depressed (deepened) thermocline are typically
expected during the spring upwelling season following an El Niño winter, and
these are similar to conditions that were present last summer long during the
massive bloom of 2015. Will the nutrient conditions be such that DA production
is favored? Will it reach the historic levels we saw in 2015 and be as
pervasive or long-lived? Time will tell, and we are mobilizing resources to
study this in greater detail as the dynamics evolve.