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Aim: The Last Glacial Maximum (LGM) remains an enigmatic period in southeast Australia due to the limited spatial and temporal resolution of its palaeoclimatic records. A major feature of the LGM landscape was the existence of the Bassian Land Bridge, joining Tasmania with the mainland of Australia during periods of low sea level, and potentially facilitating increased biotic movement between these regions. To better understand biogeographical changes on the land bridge and in southeast Australia generally during the LGM, we present a 35 ka‐year palaeoecological record from one of the larger islands of Bass Strait. Location: Bass Strait, southeast Australia. Taxon: Eucalyptus, Poaceae, Monotoca, Myriophyllum, Zygnemataceae, Botryococcus, Pediastrum. Methods: Pollen, charcoal, and non‐pollen palynomorphs were analysed in a 1.75‐m sediment core from truwana/Cape Barren Island, Bass Strait, to reconstruct changes in vegetation, fire regimes and lake levels on the Bassian Land Bridge. Results were then compared to existing palaeoenvironmental studies in the region to develop a broader context of the prevailing land bridge environment and the potential influence on biotic dispersals in Australia during the last glacial period. Results: Results suggest a major vegetation shift on the Bassian Land Bridge in response to the establishment of the LGM climate, with grassland expansion at the expense of woodland from ~29–11 ka. Floristic richness, biomass burned and lake levels also markedly decreased through this period, with the driest interval being ~25–18 ka. Dryland herbaceous taxa dispersed between the mainland and Tasmania when the landbridge was fully exposed. Main conclusions: In agreement with previous studies, our results show that the dry grassland that dominated southeast Australia (and Southern Hemisphere mid‐latitude areas) during the LGM also extended across the Bassian Land Bridge. The prevailing environment on the land bridge is likely to have exerted a selective influence on biotic dispersals in Australia during glacial periods. [ABSTRACT FROM AUTHOR]

The timing and duration of the coldest period in the last glacial stage, often referred to as the last glacial maximum (LGM), has been observed to vary spatially and temporally. In Australia, this period is characterised by colder, and in some places more arid, climates than today. We applied Monte-Carlo change point analysis to all available continuous proxy records covering this period, primarily pollen records, from across Australia (n = 37) to assess this change. We find a significant change point occurred (within uncertainty) at 28.6 ± 2.8 ka in 25 records. We interpret this change as a shift to cooler climates, associated with a widespread decline in biological productivity. An additional change point occurred at 17.7 ± 2.2 ka in 24 records. We interpret this change as a shift towards warmer climates, associated with increased biological productivity. We broadly characterise the period between 28.6 (± 2.8) – 17.7 (± 2.2) ka as an extended period of maximum cooling, with low productivity vegetation that may have occurred as a combined response to reduced temperatures, lower moisture availability and atmospheric CO2. These results have implications for how the spatial and temporal coherence of climate change, in this case during the LGM, can be best interrogated and interpreted. [ABSTRACT FROM AUTHOR]

Branched glycerol dialkyl glycerol tetraether (GDGT) distributions observed in a sediment core from Lake McKenzie were utilized to quantitatively reconstruct the pattern of mean annual air temperature (MAAT) from coastal subtropical eastern Australia between 37 and 18.3calkaBP and 14.0calkaBP to present. Both the reconstructed trend and amplitude of MAAT changes from the top of the sediment core were nearly identical to a local instrumental MAAT record from Fraser Island, providing confidence that in this sediment core branched GDGTs could be used to produce a quantitative record of past MAAT. The reconstructed trend of MAAT during 37 to 18.3calkaBP and timing of the Last Glacial Maximum (LGM) in the Lake McKenzie record were in agreement with previously published nearby marine climate records. The amplitude of lower-than-present MAAT during the LGM potentially provides information on the latitude of separation of the Tasman Front from the East Australian current in the subtropical western Pacific. The Lake McKenzie record shows an earlier onset of near modern day warm temperatures in the early Holocene compared to marine records and the presence of a warmer than present day period during the mid-Holocene. [ABSTRACT FROM AUTHOR]

Abstract: Recent studies of the Last Glacial period Indo-Australian summer monsoon (IASM) have revealed links to both northern and southern hemisphere high latitude climate as well as to regional ocean conditions. Particular interest has been paid to the monsoon response to Heinrich events, with variability explained by meridional shifts in positioning of the intertropical convergence zone (ITCZ), but this model has not been adequately tested. In addition, the shorter-lived Dansgaard/Oeschger (D/O) events have not been detected (beyond D/O-1, the Bølling/Allerød) in land-based records from the Indo-Pacific, despite their prominent expression in stalagmites from southern Asia, raising questions about the sensitivity of the IASM to these events. Here we present a Southern Hemisphere stalagmite oxygen isotopic time series from Ball Gown Cave (BGC), tropical northern Australia, located on the margins of the modern austral summer ITCZ, that spans 40–31 and 27–8 ka. Elevated IASM rainfall coincides with Heinrich stadials and the Younger Dryas, while decreased rainfall characterizes D/O interstadials, a response that is anti-phased with sites spanning the Indo-Pacific Warm Pool and with Chinese records of the East Asian summer monsoon. The BGC time series thus reveals a precipitation dipole consistent with a southward (northward) migration of the ITCZ during periods of high northern latitude cooling (warming) as the primary driver of millennial-scale IASM variability during the Last Glacial period. Our record indicates a strengthening of the IASM after the Younger Dryas period, likely as a result of rising sea level and sea surface temperatures, breaking the link with the high latitudes. [Copyright &y& Elsevier]

Aim Climatic fluctuations during the Pleistocene have shaped the population structure of many extant taxa. However, few studies have examined widespread species inhabiting the Australian continent, where periods of increased aridity characterized the Pleistocene. Here we investigate the phylogeography and population history of a widespread and vagile southern Australian marsupial, the western grey kangaroo ( Macropus fuliginosus). Location Southern Australia. Methods We examined the variation of the mitochondrial DNA (mtDNA) control region from 511 individuals of M. fuliginosus sampled throughout their transcontinental distribution. Maximum likelihood and Bayesian analyses were used to investigate the phylogeography and coalescence analyses were then used to test hypothesized biogeographical scenarios. Results The combined results of the phylogeographical and coalescence analyses revealed a complex evolutionary history. Macropus fuliginosus originated in the south-west of the continent, with north-western and south-western populations subsequently diverging as a result of vicariance events during the mid-Pleistocene. Subsequent arid phases affected these populations differently. In the north-west, the expansion and contraction of the arid zone resulted in repeated vicariance events and multiple divergent north-western mtDNA subclades. In contrast, the south-western population was less impacted by climatic oscillations but gave rise to a major transcontinental eastward expansion. Main conclusions Macropus fuliginosus exhibits the genetic signature of divergence due to unidentified barriers in south-western Western Australia, while previously identified barriers across southern Australia appear to have had little impact despite evidence of a broad-scale range expansion prior to the Last Glacial Maximum (LGM). This pattern of localized expansion and contraction is comparable to unglaciated regions in both the Northern and Southern Hemispheres. Furthermore, this study indicates that despite the potential similarities between Northern Hemisphere glaciation and the activation of dune systems in the Australian arid zone, both of which rendered large areas inhospitable, the biotic responses and resultant phylogeographical signatures are dissimilar. Whereas a limited number of major geographically concordant refugia are observed in glaciated areas, the Southern Hemisphere arid zone appears to be associated with multiple species-specific idiosyncratic refugia. [ABSTRACT FROM AUTHOR]

The bathyal Ocean Drilling Program Site 765 at 5725 m water depth, offshore northwest Australia at 16°S is directly under the influence of the Australian monsoon during the Austral summer and is the recipient of continental dust during the Austral winter. It is downstream of the Indonesian Throughflow, which is a major arm of the global thermohaline circulation. As such it is ideally situated to record the climate and oceanic consequences of Quaternary climate variability. Despite being over 400 km from northwest Australia, palynomorphs (pollen and spores) are relatively common in this section, sourced via aeolian (during the dry winter) and benthic transportation processes and sediment plumes (during the summer monsoon). Detailed palynological analyses of this flora in the upper part of this core reveals intermittent snap shots of environmental and climate change over the last 300 kyrs. Interglacial stages are interpreted to be characterised by palynomorph-rich turbidite and calcareous ooze deposition whereas palynomorph-poor slowly accumulating siliceous oozes (deposited below the Calcium Carbonate Compensation Depth) are present during glacials. The dominance of Poaceae sourced from the Australian mainland in interglacial periods suggests that vegetation during these periods was similar to today. Interglacial palynofloral assemblages suggest a more intense wet season (Australian monsoon) with higher rainfall that allowed more active erosion and deposition onto the shelf. The presence of Indonesian sourced pollen and fern spore taxa, as well as warm water dinoflagellate species suggest enhanced Leeuwin Current and monsoonal intensity during interglacials times. The youngest part of the core is dominated by siliceous ooze, likely deposited during the Last Glacial Maximum and the early Holocene. The lack of calcareous ooze near the top of the core is likely caused by Holocene to Recent erosive processes or core disturbance. The presence of common charcoal in all samples over the last 300 kyrs shows that fire was a constant feature of the landscape in northwest Australia prior to human occupation of the region 65,000 years ago. • Palynomorphs in bathyal ODP Site 765 record 300kys of Quaternary climate variability. • Fossil palynomorphs are sourced via dry season aeolian or monsoonal sediment plumes. • Interglacials are turbidites/calcareous oozes whereas glacials are siliceous oozes. • Poaceae from Australia dominated interglacials due to an enhanced Australian Monsoon. • Common charcoal shows fire was a constant landscape feature prior to human occupation 65,000kyrs. [ABSTRACT FROM AUTHOR]

The Quaternary is well known for being a period of the geological record that saw significant and alternating climatic fluctuations. Here, we concentrate on the last 94 millennia that saw Australia and its surrounding seas undergo significant environmental changes. Importantly also it is during that this period of time includes the arrival and settlement of humans in Australia. Following on from Marine Isotopic Stage 4 (MIS4) that saw, over the period of 71-59 ka BP, a significant eustatic sea level drop (∼100 m), low sea-surface temperatures as well as glacial conditions on land, Australia experienced wet conditions again, but eventually progressively entered into a glacial phase. By then, humans had arrived on this large continent and later the megafauna progressively became extinct. This paper describes in detail the climate over this period, based principally on the high-resolution record of two marine sediment cores located offshore of the southern Australian margin, and that are then compared with known events on land as well as other deep-sea cores. Particular emphasis is placed on the period that spans the Last Glacial Maximum (LGM), the extent of which thus far had been poorly defined in the Australian region. Emphasis is placed on the period from 34 to 14 ka to demonstrate that (1) the LGM, defined here as the period 24 to 18 ka, was not always extremely dry and cold, and (2) that people were able to live in inland Australia as water existed in places, despite generally cold conditions. We also show using a series of ten maps - at 2 ka intervals over the 34-14 ka period - the waxing and waning of oceanic fronts such as the Subtropical and Subantarctic Fronts, link sea-surface temperatures (SST) with periods of glacial expansion in the Australian Alps and Tasmania, as well as the South Island of New Zealand, and the extent of the Leeuwin Current down to south of Australia. Aeolian dust was transported at sea over the main core site from ∼26 to 18 ka period, pointing to arid conditions in Australia, but this period was punctuated by two significant reductions in dust transport to both core sites, coinciding with a retreat of the Subantarctic Front away from the Australian southern coastline, and slight SST shifts for a few centuries at ∼24 and 22-21 ka BP. At the peak of the cold phase, from 23 to 18.4 ka, summer SST were of the order of 9 °C below that experienced during the middle of the Holocene at about 6 ka BP. A similar temperature drop was also experienced offshore the northwestern corner of Western Australia. Periglacial activity dates for the Australian mainland and Tasmania pool around ∼22 ka. On either side of the 24 ka event, the chain of lakes in the Willandra Lakes retained water and human activity was registered in the area. Elsewhere in Australia, water was present to sustain human populations during the cold and dry times. It is postulated here that northern Australia was at times quite wet, especially during MIS4. The cessation of the LGM is set on 18.4 ka from offshore southern Australia as confirmed for the deep-sea cores by several proxies, and more likely at 18 ka inland. Finally, we document that it took two millennia for "glacial" conditions to end in the Australian region as registered in our deep-sea core records, well after the lowest global sea level ∼20.6 and 20 ka, respectively, started to rise. There is also evidence of another very cold period determined on the Australian mainland, Tasmania and the South Island of New Zealand centred around 27 ka, after which time warmer conditions occurred before the start of the LGM. This is matched with our deep-sea records with very cold conditions and changes in oceanographic conditions. • 2 deep-sea cores provide information on the waxing and waning of oceanic fronts south of Australia. • The Last Glacial Maximum for the Australian region spans 24-18 ka. • 10 maps detail conditions in the Australian region spaning the period 34–14 ka. • Environmental conditions for MIS2 & MIS4 are compared in great detail in the cores. • Australia was arid and cold during the LGM but there was water to support human occupation. [ABSTRACT FROM AUTHOR]