Unravelling the dynamics of El Niño through time

We study the marine-continental El Niño climate phenomenon in the Ecuadorian Andes where it has a direct and large impact on rainfall and temperature patterns. Lake sediments provide an archive of past El Niño’s that are investigated with high-resolution microfossil and geochemical analyses.

View on a small river delta that fills up Laguna Pallcacocha in the Andes of Ecuador, at 4050 m above sea level.

El Niño is the main source of inter-annual climate variation worldwide. The behavior of this system is highly unpredictable in a warming climate. Insight into the past occurrence of El Niño provides the possibility to test climate models that are necessary to project future changes. In our Ecuador research area, rainfall is directly controlled by El Niño, and this has a major impact on the plant communities and their growth conditions. We analyze fossil pollen grains and other remains of microorganisms from sediment cores collected in high-altitude lakes in the Ecuadorian Andes. The pollen composition shows considerable change over the last 10 thousand years and changes are synchronous to the frequency of flood layers in the sediments. The record shows more ecosystem disturbance and more frequent floods in the last five thousand years, indicating that the El Niño system has become stronger with increasing impact on the landscape. This impact is amplified due to human deforestation and infrastructure. Our ongoing research attempts to carry out pollen analysis at an unprecedented single-year resolution to resolve the intensity of individual El Niño events in the past.