Australasian hydroclimate response to the collapse of the Atlantic
Meridional Overturning Circulation under pre-industrial and Last
Interglacial climates
Abstract
Abrupt climate change events during the last glacial period and the Last
Interglacial resulted from changes in the Atlantic Meridional
Overturning Circulation (AMOC). Over the last 50 years, the AMOC has
weakened and is projected to weaken further or even collapse this
century due to freshwater influx from melting glaciers driven by climate
warming. Despite numerous modelling studies investigating the impacts of
an AMOC shutdown, little is known about its impact on Australasian
hydroclimate, particularly under a climate warmer than the
pre-industrial (PI). Using the ACCESS-ESM1.5 model, we assess the
processes impacting seasonal hydroclimate in the Australasian region in
response to an AMOC shutdown under PI and Last Interglacial (LIG)
climatic conditions. While the broad hydroclimate response to an AMOC
shutdown is similar in both experiments, notable regional differences
emerge, highlighting the influence of background climate states. During
austral summer (DJF), the AMOC shutdown leads to drier conditions over
the Maritime Continent and increased precipitation over northern
Australia under both PI and LIG conditions. However, the precipitation
increase over Australia is weaker under PI than LIG. During austral
winter (JJA), mid to high southern latitude regions of Australia and New
Zealand experience drying in response to the AMOC shutdown under PI
boundary conditions, while under LIG boundary conditions, only
southeastern Australia and New Zealand exhibit drier conditions, with
northwestern Australia displaying wetter conditions. These results
underscore the complex and region-specific responses of Australasian
hydroclimate to AMOC disruptions, highlighting the importance of
considering background climate states when assessing such impacts.