ENSO signature in botanical proxy time series extends terrestrial El Niño record into the (sub)tropics

The El Niño-Southern Oscillation (ENSO) exerts significant control over the amount of Florida winter precipitation. We use a local near-annual resolved palaeobotanical proxy record from southern Florida to test for historic ENSO variability over the past 125 years. Palaeobotanical proxies from a Florida wetland, pollen counts, and a new drought-stress proxy based on leaf epidermal cell densities are used as indicators of moisture availability during the winter growing season. Spectral analysis and band-pass filtering of the proxy records reveal significant variability within the 2-7 year bandwidth characteristic of ENSO, as well as decadal signatures. A maximum likelihood palaeoprecipitation reconstruction of the pollen record based on modern vegetation distributions shows values and variability comparable to instrumental records. The approach shows the dominant control of ENSO on Florida vegetation and provides a powerful means to detect discrete ENSO variability in older intervals. Key Points We report annual resolved pollen and leaf-growth proxies from Florida peat Maximum likelihood reconstruction reproduces winter precipitation variability Signals show clear El Niño signature of winter precipitation forcing