Gonzales Angelique N.
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Denniston, Rhawn F.
Gonzales, Angelique N.
Polyak, Victor J.
Ummenhofer, Caroline C.
Lachniet, Matthew S.
Wanamaker, Alan D.
Humphreys, William F.
Assessing temporal variability in extreme rainfall events prior to the historical era is
complicated by the sparsity of long-term ‘direct’ storm proxies. Here we present a 2200-yr-long,
accurate and precisely dated record of cave flooding events from the northwest Australian tropics
that we interpret, based on an integrated analysis of meteorological data and sediment layers within
stalagmites, as representing a proxy for extreme rainfall events derived primarily from tropical
cyclones (TCs) and secondarily from the regional summer monsoon. This time series reveals
substantial multi-centennial variability in extreme rainfall, with elevated occurrence rates
characterizing the twentieth century, the period 850-1450 CE, and 50-400 CE; reduced activity
marks 1450-1650 CE and 500-850 CE. These trends are similar to reconstructed numbers of TCs in
the North Atlantic and Caribbean basins, and form temporal and spatial patterns best explained by
secular changes in the dominant mode of the El Niño-Southern Oscillation (ENSO), the primary
driver of modern TC variability. We thus attribute long-term shifts in cyclogenesis in both the
central Australian and North Atlantic sectors over the past two millennia to entrenched El Niño or
La Niña states of the tropical Pacific. The influence of ENSO on monsoon precipitation in this
region of northwest Australia is muted, but ENSO-driven changes to the monsoon may have
complemented changes to TC activity.