School of Geography, Earth and Atmospheric Sciences - Research Publications

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    On the relationship between mesoscale cellular convection and meteorological forcing: comparing the Southern Ocean against the North Pacific
    Lang, F ; Siems, ST ; Huang, Y ; Alinejadtabrizi, T ; Ackermann, L (Copernicus GmbH, 2023-12-20)
    Abstract. Marine atmospheric boundary layer (MABL) clouds cover vast areas over the ocean and have important radiative effects on the Earth's climate system. These radiative effects are known to be sensitive to the local organization, or structure, of the mesoscale cellular convection (MCC). A convolutional neural network model is used to identify the two idealized classes of MCC clouds, namely open and closed, over the Southern Ocean (SO) and Northwest Pacific (NP) from high-frequency geostationary Himawari-8 satellite observations. The results of the climatology show that MCC clouds are evenly distributed over the mid-latitude storm tracks for both hemispheres, with peaks poleward of the 40∘ latitude. Open-MCC clouds are more prevalent than closed MCC in both regions. An examination of the presumed meteorological forcing associated with open- and closed-MCC clouds is conducted to illustrate the influence of large-scale meteorological conditions. We establish the importance of the Kuroshio western boundary current in the spatial coverage of open and closed MCC across the NP, presumably through the supply of strong heat and moisture fluxes during marine cold-air outbreaks events. In regions where static stability is higher, we observe a more frequent occurrence of closed MCCs. This behavior contrasts markedly with that of open MCCs, whose formation and persistence are significantly influenced by the difference in temperature between the air and the sea surface. The occurrence frequency of closed MCC over the SO exhibits a significant diurnal cycle, while the diurnal cycle of closed MCC over the NP is less noticeable.
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    Evidence for decreased copper associated with demyelination in the corpus callosum of cuprizone-treated mice
    Hilton, JBW ; Kysenius, K ; Liddell, JR ; Mercer, SW ; Hare, DJ ; Buncic, G ; Paul, B ; Wang, Y ; Murray, SS ; Kilpatrick, TJ ; White, AR ; Donnelly, PS ; Crouch, PJ (OXFORD UNIV PRESS, 2024-01-05)
    Demyelination within the central nervous system (CNS) is a significant feature of debilitating neurological diseases such as multiple sclerosis and administering the copper-selective chelatorcuprizone to mice is widely used to model demyelination in vivo. Conspicuous demyelination within the corpus callosum is generally attributed to cuprizone's ability to restrict copper availability in this vulnerable brain region. However, the small number of studies that have assessed copper in brain tissue from cuprizone-treated mice have produced seemingly conflicting outcomes, leaving the role of CNS copper availability in demyelination unresolved. Herein we describe our assessment of copper concentrations in brain samples from mice treated with cuprizone for 40 d. Importantly, we applied an inductively coupled plasma mass spectrometry methodology that enabled assessment of copper partitioned into soluble and insoluble fractions within distinct brain regions, including the corpus callosum. Our results show that cuprizone-induced demyelination in the corpus callosum was associated with decreased soluble copper in this brain region. Insoluble copper in the corpus callosum was unaffected, as were pools of soluble and insoluble copper in other brain regions. Treatment with the blood-brain barrier permeant copper compound CuII(atsm) increased brain copper levels and this was most pronounced in the soluble fraction of the corpus callosum. This effect was associated with significant mitigation of cuprizone-induced demyelination. These results provide support for the involvement of decreased CNS copper availability in demyelination in the cuprizone model. Relevance to human demyelinating disease is discussed.
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    Current extent and future opportunities for living shorelines in Australia.
    Morris, RL ; Campbell-Hooper, E ; Waters, E ; Bishop, MJ ; Lovelock, CE ; Lowe, RJ ; Strain, EMA ; Boon, P ; Boxshall, A ; Browne, NK ; Carley, JT ; Fest, BJ ; Fraser, MW ; Ghisalberti, M ; Gillanders, BM ; Kendrick, GA ; Konlechner, TM ; Mayer-Pinto, M ; Pomeroy, AWM ; Rogers, AA ; Simpson, V ; Van Rooijen, AA ; Waltham, NJ ; Swearer, SE (Elsevier BV, 2024-03-20)
    Living shorelines aim to enhance the resilience of coastlines to hazards while simultaneously delivering co-benefits such as carbon sequestration. Despite the potential ecological and socio-economic benefits of living shorelines over conventional engineered coastal protection structures, application is limited globally. Australia has a long and diverse coastline that provides prime opportunities for living shorelines using beaches and dunes, vegetation, and biogenic reefs, which may be either natural ('soft' approach) or with an engineered structural component ('hybrid' approach). Published scientific studies, however, have indicated limited use of living shorelines for coastal protection in Australia. In response, we combined a national survey and interviews of coastal practitioners and a grey and peer-reviewed literature search to (1) identify barriers to living shoreline implementation; and (2) create a database of living shoreline projects in Australia based on sources other than scientific literature. Projects included were those that had either a primary or secondary goal of protection of coastal assets from erosion and/or flooding. We identified 138 living shoreline projects in Australia through the means sampled starting in 1970; with the number of projects increasing through time particularly since 2000. Over half of the total projects (59 %) were considered to be successful according to their initial stated objective (i.e., reducing hazard risk) and 18 % of projects could not be assessed for their success based on the information available. Seventy percent of projects received formal or informal monitoring. Even in the absence of peer-reviewed support for living shoreline construction in Australia, we discovered local and regional increases in their use. This suggests that coastal practitioners are learning on-the-ground, however more generally it was stated that few examples of living shorelines are being made available, suggesting a barrier in information sharing among agencies at a broader scale. A database of living shoreline projects can increase knowledge among practitioners globally to develop best practice that informs technical guidelines for different approaches and helps focus attention on areas for further research.
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    Working with care: embodying feminist care ethics in regional coworking spaces
    Crovara, E (PERGAMON-ELSEVIER SCIENCE LTD, 2023-03)
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    Freshwater mollusc sclerochronology: Trends, challenges, and future directions
    Stringer, CA ; Prendergast, AL (Elsevier BV, 2023-12-01)
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    Microphysical mechanisms of wintertime postfrontal precipitation enhancement over the Australian Snowy Mountains
    Gevorgyan, A ; Siems, S ; Huang, Y ; Ackermann, L ; Manton, M (WILEY, 2023-12-07)
    Abstract A heavy orographic precipitation event associated with the postfrontal sector of a midlatitude cyclone over the Australian Snowy Mountains (ASM) was analyzed using field observations and numerical simulations. This event, observed during a 2018 intensive field campaign, was of particular interest as three distinct precipitation episodes were identified within a prolonged postfrontal period. Deep mixed‐phase clouds (MPCs) characterized by cold cloud‐top temperatures (colder than −30°C) and the presence of updrafts extending 3.5–4.5 km above the boundary‐layer height, produced the three enhanced precipitation events over the windward slopes of the ASM. The presence of conditional instabilities and deep updrafts were also found in the sounding and Doppler velocity observations respectively, while the cloud radar observations show the deep MPCs with cloud tops reaching to 6–7 km a.s.l. Orographic convection invigoration was found to be the main mechanism producing the precipitation enhancement over the windward slopes and higher terrain. Using the Weather Research/Forecasting model, we analyzed the rates of microphysical processes to explicitly account for the enhancement of precipitation formation processes in these MPCs. This analysis showed that the precipitation formation processes were further enhanced through depositional and riming growth of ice‐phase hydrometeors during the three precipitation events. Deposition is simulated at higher levels (above the −15°C level) and most likely enabled by deep convective updrafts through the midtroposphere, whereas riming is stronger at lower levels (below −10°C level) due to the persistent production of feeder supercooled liquid water clouds sustained by the orographic lifting.
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    Elevated Southern Hemisphere moisture availability during glacial periods
    Weij, R ; Sniderman, JMK ; Woodhead, JD ; Hellstrom, JC ; Brown, JR ; Drysdale, RN ; Reed, E ; Bourne, S ; Gordon, J (NATURE PORTFOLIO, 2024-02-08)
    Late Pleistocene ice-age climates are routinely characterized as having imposed moisture stress on low- to mid-latitude ecosystems1-5. This idea is largely based on fossil pollen evidence for widespread, low-biomass glacial vegetation, interpreted as indicating climatic dryness6. However, woody plant growth is inhibited under low atmospheric CO2 (refs. 7,8), so understanding glacial environments requires the development of new palaeoclimate indicators that are independent of vegetation9. Here we show that, contrary to expectations, during the past 350 kyr, peaks in southern Australian climatic moisture availability were largely confined to glacial periods, including the Last Glacial Maximum, whereas warm interglacials were relatively dry. By measuring the timing of speleothem growth in the Southern Hemisphere subtropics, which today has a predominantly negative annual moisture balance, we developed a record of climatic moisture availability that is independent of vegetation and extends through multiple glacial-interglacial cycles. Our results demonstrate that a cool-moist response is consistent across the austral subtropics and, in part, may result from reduced evaporation under cool glacial temperatures. Insofar as cold glacial environments in the Southern Hemisphere subtropics have been portrayed as uniformly arid3,10,11, our findings suggest that their characterization as evolutionary or physiological obstacles to movement and expansion of animal, plant and, potentially, human populations10 should be reconsidered.