Extensive wet episodes in Late Glacial Australia resulting from high-latitude forcings

Abstract

Millennial-scale cooling events termed Heinrich Stadials punctuated Northern Hemisphere climate during the last glacial period. Latitudinal shifts of the intertropical convergence zone (ITCZ) are thought to have rapidly propagated these abrupt climatic signals southward, influencing the evolution of Southern Hemisphere climates and contributing to major reorganisation of the global ocean-atmosphere system. Here, we use neodymium isotopes from a marine sediment core to reconstruct the hydroclimatic evolution of subtropical Australia between 90 to 20 thousand years ago. We find a strong correlation between our sediment provenance proxy data and records for western Pacific tropical precipitations and Australian palaeolakes, which indicates that Northern Hemisphere cooling phases were accompanied by pronounced excursions of the ITCZ and associated rainfall as far south as about 32°S. Comparatively, however, each of these humid periods lasted substantially longer than the mean duration of Heinrich Stadials, overlapping with subsequent warming phases of the southern high-latitudes recorded in Antarctic ice cores. In addition to ITCZ-driven hydroclimate forcing, we infer that changes in Southern Ocean climate also played an important role in regulating late glacial atmospheric patterns of the Southern Hemisphere subtropical regions.

Preferential Riverine Export of Fine Volcanogenic Particles to the Southeast Australian Margin

“…Core MD03-2607 provides a continuous record of sediment export and environmental changes from the MDB during the last two glacial/interglacial cycles (viz. 250 kyr) (Gingele et al, 2004;Gingele and De Deckker, 2005a;Lopes dos Santos et al, 2013;Bayon et al, 2017;De Deckker et al, 2019). During glacial periods and associated sea-level lowstands of the Late Quaternary, the River Murray discharged directly at the edge of the continental shelf, resulting in enhanced delivery of terrigenous sediment to the Murray Canyons area (Gingele et al, 2004).…”

“…During glacial periods and associated sea-level lowstands of the Late Quaternary, the River Murray discharged directly at the edge of the continental shelf, resulting in enhanced delivery of terrigenous sediment to the Murray Canyons area (Gingele et al, 2004). In this study, we chose specifically to analyze sediments deposited during sea-level lowstands, when detrital sedimentation at site MD03-2607 was dominated by river inputs from the MDB (Bayon et al, 2017). A total of 24 samples were analyzed from two sediment intervals: (1) between 210-390 cm depth (∼19-28 kyr BP; i.e., the Last Glacial Maximum); (2) between 810 and 870 cm depth (∼60-70 kyr BP; i.e., Marine Isotope Stage MIS 4).…”

“…Neodymium isotopic measurements on fecal pellet separates were performed at the Pôle Spectrométrie Océan (Brest, France) using a Thermo Fisher Scientific Neptune multi-collector ICPMS, after Nd purification by ion exchange chromatography (Bayon et al, 2012). Note that Nd isotopic data for the fine-grained (<4 µm) detrital sediment in core MD03-2607 were already reported in Bayon et al (2017), as part of a study that aimed at reconstructing the evolution of sediment provenance during the last glacial period and its link to past hydroclimatic changes in southeast Australia. Due to small sample size (typically just a few mg), the in-run analytical uncertainties associated with Nd isotopic measurements of copepod fecal pellets were generally larger (from ±0.2 to 0.7 ε; 2 se) than the external reproducibility determined from repeated analyses of the JNd-i solution (±0.12ε; 2 SD; n = 5).…”

“…Rare earth element and Nd isotopic composition of fine-grained (<4 µm) detrital fractions (core MD03-2607). Nd isotopic compositions (εNd ± 0.17) are fromBayon et al (2017). b REE concentrations are from this study.…”

Understanding the Australian Monsoon change during the Last Glacial Maximum with a multi-model ensemble

“…With strong climatic forcings (including low greenhouse gas (GHG) concentrations, large ice sheets, and low sea level, etc. ), the Last Glacial Maximum (LGM) is one of the key periods that provides an opportunity to better understand the mechanisms of how global and regional climate respond to external forcings (Hewitt et al, 2001;Braconnot et al, 2007Braconnot et al, , 2012aHarrison et al, 2014). Previous studies have investigated how the external forcings and boundary conditions during the LGM affected the Intertropical Convergence Zone (ITCZ) (Broccoli et al, 2006;Donohoe et al, 2013;McGee et al, 2014), the Walker circulation (DiNezio et al, 2011), the Indo-Pacific climate (Xu et al, 2010;DiNezio and Tierney, 2013;DiNezio et al, 2016), the Southern Hemisphere (SH) circulation (Rojas, 2013), and the global monsoon (Jiang et al, 2015;Yan et al, 2016).…”