Abstract

Tropical El Ni~no Southern Oscillation (ENSO) is an important influence on natural systems and cultural
change across the Pacific Ocean basin. El Ni~no events result in negative moisture anomalies in the
southwest Pacific and are implicated in droughts and catastrophic wildfires across eastern Australia. An
amplification of tropical El Ni~no activity is reported in the east Pacific after ca. 6.7 ka; however, proxy
data for ENSO-driven environmental change in Australia suggest an initial influence only after ca. 5 ka.
Here, we reconstruct changes in vegetation, fire activity and catchment dynamics (e.g. erosion) over the
last 14.6 ka from part of the southwest Pacific in which ENSO is the main control of interannual
hydroclimatic variability: Paddy's Lake, in northwest Tasmania (1065 masl), Australia. Our multi-proxy
approach includes analyses of charcoal, pollen, geochemistry and radioactive isotopes. Our results
reveal a high sensitivity of the local and regional vegetation to climatic change, with an increase of nonarboreal
pollen between ca. 14.6e13.3 ka synchronous with the Antarctic Cold Reversal, and a sensitivity
of the local vegetation and fire activity to ENSO variability recorded in the tropical east Pacific through
the Holocene. We detect local-scale shifts in vegetation, fire and sediment geochemistry at ca. 6.3, 4.8
and 3.4 ka, simultaneous with increases in El Ni~no activity in the tropical Pacific. Finally, we observe a
fire-driven shift in vegetation from a pyrophobic association dominated by rainforest elements to a
pyrogenic association dominated by sclerophyllous taxa following a prolonged (>1 ka) phase of tropical
ENSO-amplification and a major local fire event at ca. 3.4 ka. Our results reveal the following key insights:
(1) that ENSO has been a persistent modulator of southwest Pacific climate and fire activity
through the Holocene; (2) that the climate of northwest Tasmania is sensitive to long-term shifts in
tropical ENSO variability; and (3) that there has been possible stationarity in the spatial influence of
ENSO over this region through the Holocene.