Extreme rainfall activity in the Australian tropics reflects changes in the El NiÃ±o/Southern Oscillation over the last two millennia

Rhawn F Denniston; Gabriele Villarini; Angelique N Gonzales; Karl-Heinz Wyrwoll; Victor J Polyak; Caroline C Ummenhofer; Matthew S Lachniet; Alan D Wanamaker; William F Humphreys; David Woods; John Cugley

doi:10.1073/pnas.1422270112

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Extreme rainfall activity in the Australian tropics reflects changes in the El NiÃ±o/Southern Oscillation over the last two millennia

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Extreme rainfall activity in the Australian tropics reflects changes in the El NiÃ±o/Southern Oscillation over the last two millennia

Rhawn F Denniston, Gabriele Villarini, Angelique N Gonzales, Karl-Heinz Wyrwoll, Victor J Polyak, Caroline C Ummenhofer, Matthew S Lachniet, Alan D Wanamaker, William F Humphreys, David Woods, …

Proceedings of the National Academy of Sciences - PNAS, Vol.112(15), pp.4576-4581

04/14/2015

DOI: 10.1073/pnas.1422270112

PMCID: PMC4403187

PMID: 25825740

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Abstract

Variations in tropical cyclone (TC) activity are poorly known prior to the twentieth century, complicating our ability to understand how cyclogenesis responds to different climate states. We used stalagmites to develop a near-annual record of cave flooding from the central Australian tropics, where TCs are responsible for the majority of extreme rainfall events. Our 2,200-year time series reveals shifts in the mean number of storms through time, similar to TC variability from the North Atlantic. This finding is consistent with modern relationships between El Niño/Southern Oscillation (ENSO) and cyclogenesis, as well as with the reconstructed state of ENSO over the past two millennia, suggesting that changes between La Niña- and El Niño-dominated periods drove multicentennial shifts in TC activity in both basins. 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.

Australia

ENSO

flood

Physical Sciences

stalagmite

tropical cyclone

Details

Title: Subtitle: Extreme rainfall activity in the Australian tropics reflects changes in the El NiÃ±o/Southern Oscillation over the last two millennia
Creators: Rhawn F Denniston - Cornell College
Gabriele Villarini - University of Iowa
Angelique N Gonzales - Cornell College
Karl-Heinz Wyrwoll - School of Earth and Environment
Victor J Polyak - University of New Mexico
Caroline C Ummenhofer - Woods Hole Oceanographic Institution
Matthew S Lachniet - University of Nevada, Las Vegas
Alan D Wanamaker - Iowa State University
William F Humphreys - hWestern Australia Museum, Welshpool DC, WA 6986, Australia;
David Woods - iDepartment of Parks and Wildlife, Broome, WA 6725, Australia; and
John Cugley - jAustralian Speleological Federation, Willetton, WA 6155, Australia
Resource Type: Journal article
Publication Details: Proceedings of the National Academy of Sciences - PNAS, Vol.112(15), pp.4576-4581
DOI: 10.1073/pnas.1422270112
PMID: 25825740
PMCID: PMC4403187
NLM abbreviation: Proc Natl Acad Sci U S A
ISSN: 0027-8424
eISSN: 1091-6490
Publisher: National Academy of Sciences
Grant note: research grant / Kimberley Foundation Australia internal funds / Penzance and John P. Chase Memorial Endowed Funds (Woods Hole) seed grant / Cornell College seed grant / Center for Global and Regional Environmental Research AGS 1103413 / National Science Foundation
Alternative title: 2,200 y of ENSO, cyclones, and Australian floods
Language: English
Date published: 04/14/2015
Academic Unit: Civil and Environmental Engineering; Earth and Environmental Sciences; IIHR--Hydroscience and Engineering
Record Identifier: 9984197519402771

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