El Niño eclipsa la señal de cambio de régimen en el Norte del Ecosistema de la Corriente de Humboldt

In the Northern Humboldt Current System (NHCS) the main interannual climatic fluctuation is the El Niño (EN) warm phase of El Niño Southern Oscillation (ENSO) cycle, while on a pan-Pacific scale, the main interdecadal climatic fluctuation is the Pacific Decadal Oscillation (PDO). In addition, the regime shift (RS) have been associated to shifts in PDO. Thus a main RS occurred during 1975-1976 was the result of global scale ocean-atmosphere processes. However, the PDO has not been had persistence or regime like character in the last 20 years. The effects of EN and RS on sea surface temperature (SST), sea level pressure (SLP), and upwelling index Callao (UIC) in the NHCS are here examined and correlated with biological components of the ecosystem. Long-term time series (1950-2006) of physical (SST, SLP and UI) and biological variables (microphytoplankton, mesozooplankton and pelagic biomasses) off Peru are examined by classical running average techniques, a multivariate autoregressive model and wavelets analysis.

The EN phases, PDO and RS were highly significant for the physical time series; for example the first principal component (PC1) of SST along the Peruvian coast explained 87% of the total variance in SST. However, EN had more influence than RS on the global wavelet spectrum variance: 39% for EN phase and 9% for climatic RS. Overall, EN phases were coherent with both physical and biological time series along the coast off Peru. Conversely, the mesozooplankton data sets were only reflected by interdecadal trends, like to PDO; however, the RS’s were not synchronous in interdecadal fluctuations. The EN phase and PDO were significant for top trophic level biological data, but the RS test was not significant for bottom trophic level biological time series. Our main results suggest that there is a strong EN signal in physical and biological time series, and that it introduces the high frequency spectrum in the RS. The EN phases overshadow the RS in the NHCS and lead to interannual fluctuations in the NHCS.

Keywords: Peru, El Niño phase, ENSO, PDO, regime shift, multidecadal variability

El Niño eclipsa la señal de cambio de régimen en el Norte del Ecosistema de la Corriente de Humboldt by Sara Purca is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Based on a work at sarapurca.blogspot.com.