Monsun El Nino

The El Niño Southern Oscillation is the major source of global interannual climate variability. However, little is known about the long-term variability of this phenomenon.

Oceanography and climate along the coast of Peru are fundamentally linked to ENSO variability. Between the El Niño events, extensive upwelling of cool and nutrient-rich water makes the Peruvian continental shelf one of the most bioproductive marine systems. Organic matter decay causes strong oxygen minimum conditions between 50 and 650 m water depths, favouring the preservation of laminated diatomaceous and diatom bearing oozes.

During El Niño events, upwelling of nutrient rich water (and therefore bioproduction) is subdued and extensive rainfall reaches into some regions of otherwise (hyper-) arid coastal deserts. Precipitation run-off erodes fine-grained lithics from soils. These are flushed via rivers into the sea where they are dispersed over hundreds of kilometres along the continental shelf by the Peru Current. Sedimentary archives on the outer continental shelf thus can integrate the discharge of riverine lithic suspension from a great number of river catchments along the Peruvian coast.

Sediment cores with laminated marine sediments were recovered on the continental shelf and slope off Peru between 9°S and 14°S during cruise SO-147 with the German Research Vessel Sonne. (For impressions on the work onboard a research vessel see right hand column.)

We use the fine-grained lithic fraction and the photosynthetic pigments in the sediments and sea surface temperature reconstructions from alkenones as proxies for paleo El Niño activity.

In-situ reflectance spectroscopy techniques developed during this project revealed proxy data from these cores which resolve interannual variability during the last two interglacial periods and Terminations since 130,000 years ago. Glacial periods are resolved with decadal to multi-decadal resolution.