Bachelor of Environmental Science (Honours)
School of Earth, Atmospheric and Life Sciences
Melleuish, Josh, Reconstructing northern Australian rainfall and the Central Indo-Pacific InterTropical Convergence Zone, Bachelor of Environmental Science (Honours), School of Earth, Atmospheric and Life Sciences, University of Wollongong, 2021.
The InterTropical Convergence Zone (ITCZ) delivers intense precipitation for the tropical regions of the globe. The Australian tropics receives ~80% of its annual mean rainfall in the wet season (November-April), influenced by the arrival of the Australian Summer Monsoon (ASM) as the ITCZ moves south of the equator. Northern Australian rainfall projections are uncertain due to a paucity in understanding the ITCZ dynamics, the ITCZ/ASM relationship, and the large internal variability of these climatic phenomena. This study explores Central-Indo-Pacific (CIP) ITCZ dynamics, using a new set of indices that better capture the ITCZ intensity, latitudinal width, centre and southern edge positions (S_edge); and by using the Sr/Ca record measured in a speleothem collected from Katherine, Northern Territory, Australia. Over the instrumental period, increases in ASM intensity and rainfall are correlated with southward latitudinal movements of the southern ITCZ edge (r = -0.71, -0.73 respectively, p < 0.01). The southern edge is a function of ITCZ position and width, highlighting the problems with linking changes in paleo-ASM rainfall to latitudinal ITCZ movements alone. The southern ITCZ edge position is dominated by 3-year interannual variance, punctuated by shorter periods of ~7-year variance, over the instrumental period. The Sr/Ca records, covering ~1429-1478, ~1761-1777, ~1851-1870 and ~1885-1933, show robust seasonal signals modulated by hydrological change that also reflect S_edge and the dominance of 3- and 7-year periodicities. The 3-year cycling brings more intense rainfall totals and seasonality to the northern Australian region relative to the 7-year frequency, but longer Sr/Ca records are needed to assess their drivers.
FoR codes (2008)
960202 Atmospheric Processes and Dynamics
Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.