Macias, D., M. R. Landry, A. Gershunov, A. J. Miller and P. S. Franks, 2012:
Climatic control of upwelling variability along the western North-American Coast.
PLoS ONE, 7, e30436, doi:10.1371/journal.pone.0030436.
The high biological production of the California Current System (CCS) results from the
seasonal development of equatorward alongshore winds that drive coastal upwelling.
While several climatic fluctuation patterns influence the dynamics and biological
productivity of the CCS, including the El Niñouthern Oscillation (ENSO), the
Pacific Decadal Oscillation index (PDO) and the North Pacific Gyre Oscillation
(NPGO), the mechanisms of interaction between climatic oscillations and the CCS
upwelling dynamics have remained obscure. Here, we use Singular Spectral Analysis
(SSA) to reveal, for the first time, low-frequency concordance between the time series
of climatic indices and upwelling intensity along the coast of western North America.
Based on energy distributions in annual, semiannual and low-frequency signals, we can
divide the coast into three distinct regions. While the annual upwelling signal dominates
the energy spectrum elsewhere, low-frequency variability is maximal in the regions
south of 33N. Non-structured variability associated with storms and turbulent mixing is
enhanced at northerly locations. We found that the low-frequency signal is significantly
correlated with different climatic indices such as PDO, NPGO and ENSO with the
correlation patterns being latitude-dependent. We also analyzed the correlations
between this upwelling variability and sea surface temperature (SST) and sea level
pressure (SLP) throughout the North Pacific to visualize and interpret the large-scale
teleconnection dynamics in the atmosphere that drive the low-frequency coastal winds.
These results provide new insights into the underlying mechanisms connecting climatic
patterns with upwelling dynamics, which could enhance our prediction and forecast
capabilities of the effects of future oceanographic and climatic variability in the CCS.