The impacts of an AMOC slowdown on Australian climate at 8.2 ka in
ACCESS-ESM1.5 model
Abstract
Greenland ice cores reveal an abrupt cooling of up to 3.3°C 8.2 kyr ago
(8.2 ka), lasting for roughly 160 years. The event was likely caused by
a weakening of the Atlantic Meridional Overturning Circulation (AMOC)
due to freshwater drainage into the North Atlantic. It was associated
with a global-scale climate change but is recorded in very few
high-resolution paleoclimatic time series from the Southern Hemisphere
(SH). In this study, we investigate the 8.2 ka event in the SH,
particularly the Australian climate response to a weakened AMOC. Five
North Atlantic meltwater experiments are conducted with the Australian
Earth System Model, ACCESS-ESM1.5, to evaluate the sensitivity of AMOC
responses to freshwater perturbations under early Holocene conditions as
well as their climate impact. Our results suggest a 100-year freshwater
pulse reproduces a global climate change that best matches existing
proxy records for the 8.2 ka event. Australian surface air temperatures
show significant cooler conditions in the northern half of the continent
but warmer anomalies in the south in response to a weakened AMOC.
Australian hydroclimate displays a more complex response at 8.2 ka.
Northern Australian precipitation is influenced by a southward shift in
the mean position of the Intertropical Convergence Zone and a
strengthened Indo-Australian summer monsoon, while the southern part of
the continent is more sensitive to weakening of the winter westerly
winds. These results highlight the importance of understanding the
Australian climate response to a weakened AMOC under different
background climate in order to better predict potential future impacts.