Holocene hydroclimate inferred from alkane isotope and pollen records from monsoonal northern Australia

Terrestrial proxy records of environmental change from the southern end of the coupled East Asian-IndoAustralian monsoon domain remain limited in number. Here we present multi-proxy Holocene n -alkane hydrogen isotope and pollen records from Girraween Lagoon, located in monsoonal northern Australia. We compare the Girraween record with two published speleothem isotope records available to the north and south of the lagoon, all within the region where rainfall is dominantly associated with the southward movement of the Intertropical Convergence Zone (ITCZ) in the Austral summer. All three sites record an initial period of general monsoon intensification between ~7.5 and 9 ka, but after this time the responses of the three records diverge. The records from the northern and southern sites reflect changes in the mean position of the ITCZ at its periphery that did not impact the Girraween site. The Girraween record clearly demonstrates a period of particularly enhanced monsoon rainfall between 3 and 5 ka. This period, when rainfall was dominated by deep convection was initiated by a sustained southerly shift in mean ITCZ position, which also resulted in a reduction in rainfall in southern Indonesia. Weakening of the monsoon at the Girraween site was initiated by strengthened ENSO teleconnections at 2.5–3 ka and was accompanied movement of the ITCZ to a more northerly position resulting in enhanced rainfall in southern Indonesia. The monsoon regime that was fully established by ~2 ka at Girraween Lagoon, has broadly been in place since that time. • n -alkane hydrogen isotope and pollen record from northern Australia over the Holocene • initial period of general monsoon intensification between ~7.5 and 9 ka, • particularly enhanced monsoon rainfall between 3 and 5 ka • Weakening of the monsoon initiated by strengthened ENSO teleconnections at 2.5–3 ka • The modern monsoon regime that was fully established by ~2 ka