El Niño: The dominant mode of global climate and ocean ecosystem variability

Background/Question/Methods In this presentation long (~100 year) global time series of sea surface temperature (SST) and sea level pressure (SLP) are analyzed to describe the dominant modes of variability. After removing the long term trends and the seasonal cycle at each pixel, the first four modes of SST are well correlated with 4 well-known indices. Shorter time series of more recent satellite time series of chlorophyll, primary production, surface irradiance, winds and sea level are also analyzed. Model solutions are capable of resolving this variability and are used to further describe oceanographic changes. In situ data from Peru, California and Galapagos are analyzed to show further ecosystem impacts of the first mode. These results together with those from other papers delivered in the Symposium are used to synthesize the ecological consequences of El Nino in the Galapagos Islands. The primary question is how clearly can the impacts of El Nino, on global fields and the Galapagos ecosystems in particular, be resolved.

Results/Conclusions El Nino and its atmospheric counterpart the Southern Oscillation (ENSO) remain as the dominant forms of ocean and atmosphere variability. This is evident in the global correlations of the multiple environmental time series with ENSO indices. Given the strong signature of the phenomena its impacts on ocean ecosystems, and in particular those in direct contact with the region of strongest impact, the eastern equatorial Pacific, are clearly visible. The ecosystem impacts of ENSO in areas like the Galapagos Islands emerge as the poster child regarding the importance of climate change on the structure and abundance of marine populations.