RAPID: Galapagos lake chemistry and plankton assemblage during the 2015-16 El Nino

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Robust reconstructions of tropical Pacific climate are critically important for understanding past climate change due to the unique ability of this region to influence climate on a global scale. The El Niño-Southern Oscillation (ENSO) affects precipitation and temperature patterns across more than half of the globe every 3-7 years. Impacts associated with ENSO include drought, flooding, crop failure, disease, and changes in ocean productivity. Importantly, large uncertainties exist regarding how ENSO has changed in the past and how it is likely to change in a higher CO2 world. Improving ENSO reconstructions from the vastly under-sampled eastern equatorial Pacific will help elucidate the response of ENSO to large-scale changes in the climate system and thus poses tremendous benefit to society. Freshwater and coastal saline lake sediments in the Galápagos Islands provide invaluable long continuous reconstructions of rainfall from the eastern equatorial Pacific, where annual rainfall is strongly correlated to El Niño sea surface temperatures. To date, however, such reconstructions have been hampered by large uncertainties owing to the lack of direct measurements of the response of Galápagos lakes to El Niño conditions.This project seeks to leverage the 2015-2016 strong El Niño event that is currently underway to improve constraints on these and future rainfall reconstructions from the tropical Pacific. Towards this end, a comprehensive set of meteorological and lake measurements will be taken at El Junco Lake (San Cristobal Island) and Poza del Diablo and Poza Verde (Isabela Island) during the onset, peak, and decay phase of the El Niño event in collaboration with Equadorian scientists and the Charles Darwin Research Station. Measurements will include hydrologic fluxes (precipitation, evaporation) and their isotopic composition (d2Hrain), as well as physical, chemical, and biological properties of the lakes (d2Hlake, temperature, salinity, nutrients, pH, phytoplankton assemblage, depth, and d2H of plant and algal biomarkers). These data will enable the relationship between modern climate and the paleoclimate proxies to be explicitly evaluated through the course of a rare strong El Niño event (the last of which occurred 18 years ago). This dataset would be the most comprehensive characterization of the influence of El Niño events on these lake systems to date and would greatly advance ongoing efforts to construct quantitative paleo-ENSO records from this region. The work is supported by Marine Geology and Geophysics, Earth Sciences Global Change, and the Office of International Science and Engineering.