title: Extreme rainfall activity in the Australian tropics reflects changes in the El Niño/Southern Oscillation over the last two millennia.
abstract: Assessing temporal variability in extreme rainfall events before the historical era is complicated by the sparsity of long-term "direct" storm proxies. Here we present a 2,200-y-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 multicentennial variability in extreme rainfall, with elevated occurrence rates characterizing the twentieth century, 850-1450 CE (Common Era), 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 they 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.
authors.affiliation: Department of Geology, Cornell College, Mount Vernon, IA 52314; rdenniston@cornellcollege.edu.
authors.forename: Rhawn F
authors.initials: RF
authors.lastname: Denniston
authors.affiliation: IIHR-Hydroscience & Engineering, University of Iowa, Iowa City, IA 52240;
authors.forename: Gabriele
authors.initials: G
authors.lastname: Villarini
authors.affiliation: Department of Geology, Cornell College, Mount Vernon, IA 52314;
authors.forename: Angelique N
authors.initials: AN
authors.lastname: Gonzales
authors.affiliation: School of Earth and Environment, University of Western Australia, Crawley, WA 6009, Australia;
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Wyrwoll
authors.affiliation: Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131;
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Polyak
authors.affiliation: Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;
authors.forename: Caroline C
authors.initials: CC
authors.lastname: Ummenhofer
authors.affiliation: Department of Geoscience, University of Nevada, Las Vegas, NV 89154;
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Lachniet
authors.affiliation: Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011;
authors.forename: Alan D
authors.initials: AD
authors.lastname: Wanamaker
authors.affiliation: Western Australia Museum, Welshpool DC, WA 6986, Australia;
authors.forename: William F
authors.initials: WF
authors.lastname: Humphreys
authors.affiliation: Department of Parks and Wildlife, Broome, WA 6725, Australia; and.
authors.forename: David
authors.initials: D
authors.lastname: Woods
authors.affiliation: Australian Speleological Federation, Willetton, WA 6155, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Cugley
keywords: Australia; ENSO; flood; stalagmite; tropical cyclone
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