9,935 research outputs found
Enhanced carbon dioxide outgassing from the eastern equatorial Atlantic during the last glacial
No full textBiological productivity and carbon export in the equatorial Atlantic are thought to have been dramatically higher during the last glacial period than during the Holocene. Here we reconstruct the pH and CO2 content of surface waters from the eastern equatorial Atlantic Ocean over the past ?30 k.y. using the boron isotope composition of Globigerinoides ruber (a mixed-layer–dwelling planktic foraminifera). Our new record, combined with previously published data, indicates that during the last glacial, in contrast to today, a strong west to east gradient existed in the extent of air:sea equilibrium with respect to pCO2 (?pCO2), with the eastern equatorial Atlantic acting as a significant source of CO2 (+100 ?atm) while the western Atlantic remained close to equilibrium (+25 ?atm). This pattern suggests that a fivefold increase in the upwelling rate of deeper waters drove increased Atlantic productivity and large-scale regional cooling during the last glacial, but the higher than modern ?pCO2 in the east indicates that export production did not keep up with enhanced upwelling of nutrients. However, the downstream decline of ?pCO2 provides evidence that the unused nutrients from the east were eventually used for biologic carbon export, thereby effectively negating the impact of changes in upwelling on atmospheric CO2 levels. Our findings indicate that the equatorial Atlantic exerted a minimal role in contributing to lower glacial-age atmospheric CO2
Seawater pH, pCO2 and [CO2?3] variations in the Caribbean Sea over the last 130 kyr: A boron isotope and B/Ca study of planktic foraminifera
No full textRelationship between sea level and climate forcing by CO2 on geological timescales
No full textOn 103- to 106-year timescales, global sea level is determined largely by the volume of ice stored on land, which in turn largely reflects the thermal state of the Earth system. Here we use observations from five well-studied time slices covering the last 40 My to identify a well-defined and clearly sigmoidal relationship between atmospheric CO2 and sea level on geological (near-equilibrium) timescales. This strongly supports the dominant role of CO2 in determining Earth’s climate on these timescales and suggests that other variables that influence long-term global climate (e.g., topography, ocean circulation) play a secondary role. The relationship between CO2 and sea level we describe portrays the “likely”(68% probability) long-term sea-level response after Earth system adjustment over many centuries. Because it appears largely independent of other boundary condition changes, it also may provide useful long-range predictions of future sea level. For instance, with CO2 stabilized at 400–450 ppm (as required for the frequently quoted “acceptable warming” of 2 °C), or even at AD 2011 levels of 392 ppm, we infer a likely (68% confidence) long-term sea-level rise of more than 9 m above the present. Therefore, our results imply that to avoid significantly elevated sea level in the long term, atmospheric CO2 should be reduced to levels similar to those of preindustrial times
Portrait of author David Foster at the National Library of Australia, Canberra, 8 June 2011 /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author David Foster at the National Library of Australia, Canberra, 8 June 2011.; Acquired in digital format; access copy available online.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
Author David Foster with academic Jeff Doyle at the National Library of Australia, Canberra, 8 June 2011 /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author David Foster at the National Library of Australia, Canberra, 8 June 2011.; Acquired in digital format; access copy available online.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
Author David Foster and academic Jeff Doyle at the National Library of Australia, Canberra, 8 June 2011 /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author David Foster at the National Library of Australia, Canberra, 8 June 2011.; Acquired in digital format; access copy available online.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
Mountain uplift and the glaciation of North America – a sensitivity study
No full textThe Miocene (24 to 5 million years ago) wasa period of relative global warmth compared to the Quaternary(2 million years ago to present; e.g. Zachos et al.,2001) and was characterised by the intermittent glaciationof Antarctica only. Paradoxically, the majority of availableproxy data suggest that during the Miocene, pCO2 was similar,or even lower, than the pre-industrial levels (280 ppmv;Pagani et al., 1999; Pearson and Palmer, 2000; K¨urschneret al., 1996, 2008) and at times probably crossed the modelledthreshold value required for sustained glaciation in theNorthern Hemisphere (DeConto et al., 2008). Records ofice rafted debris and the oxygen isotope composition of benthicforaminifera suggest that at several times over the last25 million years substantial amounts of continental ice didbuild up in the Northern Hemisphere but none of these ledto prolonged glaciation. In this contribution, we review evidencethat suggests that in the Miocene the North AmericanCordillera was, at least in parts, considerably lower than today.We present new GCM simulations that imply that smallamounts of uplift of the North American Cordillera resultin significant cooling of the northern North American Continent.Offline ice sheet modelling, driven by these GCMoutputs, suggests that with a reduced topography, inceptionof the Cordilleran ice sheet is prohibited. This suggests thatuplift of the North American Cordillera in the Late Miocenemay have played an important role in priming the climate forthe intensification of Northern Hemisphere glaciation in theLate Pliocene
Insights into the patterns and locations of erosion in the Himalaya — A combined fission-track and in situ Sm–Nd isotopic study of detrital apatite
No full textUnderstanding the role that climate, erosion and tectonics play in determining the mean relief, elevation and general form of a mountain range over time has become the focus of much recent research in the field of tectonic geomorphology. A crucial constraint in these studies is the long-term exhumation rate, which is increasingly being examined using detrital minerals from the sedimentary rock record that represent the eroded remnants of the orogen. A classic field area of such studies is the Himalayan orogen — the Earth's largest mountain range. We describe here a novel approach that uses the in situ analysis of Nd isotopes by laser ablation multicollector inductively coupled plasma mass spectrometry of fission-track dated apatite grains to unambiguously tie them to their source regions. We demonstrate the capability of this new approach on several modern and Holocene river sand samples from the Himalayan orogen and determine, because of the large isotopic differences in the constituent tectonostratigraphic units, both the location and magnitude of long-term erosion. In agreement with previous studies we are able to show that in the Central and Eastern Himalaya long-term denudation is focussed within the High Himalayan Crystalline Series (HHCS) at average rates of not, vert, similar 2 mm/yr. Average long-term rates are similar in the Western Himalaya sampled by the Indus River and largely reflect erosional denudation of the Western Indian Himalaya and the Western Syntaxis (the Nanga Parbat Haramosh Massif and South Karakoram Metamorphic Complex). Notably, the Asian continent supplies significantly more apatites to the mouth of the Indus than they do to the Bengal delta. The ability to reconstruct the patterns of long-term erosion in the Himalaya using detrital apatites from a few samples collected from major transverse drainages provides confidence in the utility of this approach to examine the locations and magnitude of long-term erosion in the past
Views of children and young people in foster care survey: education
No full textThis paper explores the educational experiences of children and young people living in foster care in Queensland. Findings are drawn from the responses of 845 children and 1180 young people to the 2011 Views of Children and Young People in Foster Care survey, which is a rich source of information about children’s and young people’s attitudes towards and perceptions of their own education. Findings relate to educational status, key markers of educational disadvantage including suspensions and exclusions, and specific problems children and young people experience at school, as well as children’s and young people’s enjoyment of school and aspirations for the future. Information about educational support, including Educational Support Plans and support provided by Child Safety Officers and Community Visitors are also presented. Where relevant, comparisons are made between the 2011 survey results and prior surveys conducted in 2006, 2007 and 2009. Relationships between key educational measures as well as relationships to other important measures of health and placement stability are also explored.
The findings suggest that children and young people continue to experience educational disadvantage, including high rates of suspension and exclusion and a range of problems at school including problems with schoolwork, bullying and behaviour and that these difficulties can be exacerbated by the child protection system, for example, through placement instability. However, there are reasons for optimism. Children and young people are overwhelmingly likely to report that they enjoy school, expect to complete Year 12 and that their teachers generally like their schoolwork. Furthermore, over time, the proportions of young people reporting that they have an Educational Support Plan have grown, and, importantly, they are more likely to report that these plans are helpful. Analyses in relation to a number of educational variables reveal that young people with a plan they consider to be helpful fare better. Children and young people were also positive about the important role that CSOs and CVs are able to play in supporting their education.
While educational disadvantage is an enduring problem, the survey findings provide evidence of progress in key areas and suggestions for how continued improvements may be made
The consequence of Quaternary changes in chemical weathering rate for ocean chemistry (abstract of paper presented at: 17th Annual V. M. Goldschmidt Conference Cologne, Germany August 2007)
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