title: Holocene carbon accumulation in the peatlands of northern Scotland

authors: Ratcliffe, Joshua Lee

subjects: Science & Technology

abstract: The response of peatland carbon accumulation to climate can be complex, with internal feedbacks and processes that can dampen or amplify responses to external forcing. Records of carbon accumulation from peat cores provide a record of carbon which persists as peat over long periods of time, demonstrating the long-term response of peatland carbon stocks to climatic events. Numerous records of long-term carbon accumulation exist globally. However, peatlands from oceanic climates, and particularly blanket bog, remain underrepresented. Scottish bogs, which collectively have more than 475 separate palaeoecological records, may prove to be a valuable resource for studying the impact of environmental change on past rates of carbon accumulation. Here we present 12 records of carbon accumulation from the north of Scotland. We support these results with a further 43 records where potential carbon accumulation is inferred from published ages. These reveal a trend of high carbon accumulation in the early Holocene, declining in the mid-to-late Holocene. The trend is consistent with accumulation profiles from other northern peatlands and is likely to have been caused by climatic cooling. Considerable variability in carbon accumulation rates between locations is apparent for the mid-to-late Holocene. We attribute to hydrologically induced changes in carbon accumulation which are likely to be inconsistent between sites.

text: Holocene carbon accumulation in the peatlands of northern Scotland The response of peatland carbon accumulation to climate can be complex, with internal feedbacks and processes that can dampen or amplify responses to external forcing. Records of carbon accumulation from peat cores provide a record of carbon which persists as peat over long periods of time, demonstrating the long-term response of peatland carbon stocks to climatic events. Numerous records of long-term carbon accumulation exist globally. However, peatlands from oceanic climates, and particularly blanket bog, remain underrepresented. Scottish bogs, which collectively have more than 475 separate palaeoecological records, may prove to be a valuable resource for studying the impact of environmental change on past rates of carbon accumulation. Here we present 12 records of carbon accumulation from the north of Scotland. We support these results with a further 43 records where potential carbon accumulation is inferred from published ages. These reveal a trend of high carbon accumulation in the early Holocene, declining in the mid-to-late Holocene. The trend is consistent with accumulation profiles from other northern peatlands and is likely to have been caused by climatic cooling. Considerable variability in carbon accumulation rates between locations is apparent for the mid-to-late Holocene. We attribute to hydrologically induced changes in carbon accumulation which are likely to be inconsistent between sites.

year: 2019

title: An assessment of the mantle and slab components in the magmas of an oceanic arc volcano: Raoul Volcano, Kermadec arc

authors: Smith, Ian E.M.

subjects: Kermadec arc

abstract: Raoul Volcano occupies a simple oceanic subduction setting in the northern part of the Kermadec arc on the Pacific–Australian convergent plate boundary. The primary inputs to the magmatic system that feeds the volcano are a subduction component derived from the subducting old Pacific oceanic lithosphere and its veneer of pelagic sediment, and the overlying peridotitic mantle wedge. Conservative trace elements that are very incompatible during mantle melting are relatively depleted in Raoul lavas indicating a source that has been depleted during an earlier melting event. Major element co-variations indicate magma genesis by 25% near fractional melting of a mantle source that is weakly depleted (2% melt extraction) relative to a fertile MORB source. An important influence on the composition of the mantle component is progressive melt extraction coupled with minimal advection of fresh material into the sub-arc zone followed by melt extraction from a melting column beneath the spreading centre of an adjacent back arc basin. High field strength element and rare earth element systematics indicate involvement of a subduction-related component of constant composition. Two fluid components can be distinguished, one enriched in large ion lithophile elements inferred to be an aqueous fluid that is continuously added to the ascending melt column and the other a less mobile fluid that transfers Th. A homogeneous subduction-related component of constant composition and magnitude arises if the slab-derived flux migrates from the slab–mantle interface to the sub-arc melting column by repeated episodes of amphibole formation and decomposition its composition is then governed by the distribution coefficients of pyroxene and its magnitude by the degree of amphibole saturation of mantle peridotite. The results from Raoul Volcano are comparable to those from other oceanic subduction-related arcs such as South Sandwich and Marianas suggesting that this is a general model for oceanic arcs.

text: An assessment of the mantle and slab components in the magmas of an oceanic arc volcano: Raoul Volcano, Kermadec arc Raoul Volcano occupies a simple oceanic subduction setting in the northern part of the Kermadec arc on the Pacific–Australian convergent plate boundary. The primary inputs to the magmatic system that feeds the volcano are a subduction component derived from the subducting old Pacific oceanic lithosphere and its veneer of pelagic sediment, and the overlying peridotitic mantle wedge. Conservative trace elements that are very incompatible during mantle melting are relatively depleted in Raoul lavas indicating a source that has been depleted during an earlier melting event. Major element co-variations indicate magma genesis by 25% near fractional melting of a mantle source that is weakly depleted (2% melt extraction) relative to a fertile MORB source. An important influence on the composition of the mantle component is progressive melt extraction coupled with minimal advection of fresh material into the sub-arc zone followed by melt extraction from a melting column beneath the spreading centre of an adjacent back arc basin. High field strength element and rare earth element systematics indicate involvement of a subduction-related component of constant composition. Two fluid components can be distinguished, one enriched in large ion lithophile elements inferred to be an aqueous fluid that is continuously added to the ascending melt column and the other a less mobile fluid that transfers Th. A homogeneous subduction-related component of constant composition and magnitude arises if the slab-derived flux migrates from the slab–mantle interface to the sub-arc melting column by repeated episodes of amphibole formation and decomposition its composition is then governed by the distribution coefficients of pyroxene and its magnitude by the degree of amphibole saturation of mantle peridotite. The results from Raoul Volcano are comparable to those from other oceanic subduction-related arcs such as South Sandwich and Marianas suggesting that this is a general model for oceanic arcs.

year: 2009

title: Investigating the Social Supports of Successful Māori Undergraduate Appellants at the University of Waikato

authors: Diamond, Danielle Jade

subjects: Social Supports

abstract: Educational disparities between Māori and non-Māori tertiary students are evident in regards to participation, retention, and completion rates at secondary and tertiary levels. Instead of focusing on negative statistics, it was of interest to investigate Māori students who had failed sufficient papers to initially be denied re-entry to university study, yet continued to attain their degrees, as a result of a successful appeal. Māori undergraduate students, who had successfully appealed from 2003-2012, were recruited for my research. The availability and utilisation of social supports were investigated, along with the decision to make an appeal, the role of cultural expectations, and barriers experienced by participants. A mixed method approach was utilised in this research through use of an adapted overarching Kaupapa Māori framework, statistical analysis, and 13 interviews. My research found that social supports were beneficial for participants throughout their appeal, as they provided: emotional, instrumental, appraisal, and informational support. Although the social supports utilised by participants were satisfactory, barriers to accessing formal supports were also found, which included: perceived stigma having failed their papers, pride, as well as being whakamā. The appeal process was a beneficial intervention from the University of Waikato, which provided participants another opportunity to overcome the factors that contributed to their initial failure. Post appeal, participants implemented strategies to address and reduce their factors in order to become academically engaged. Participants were deemed to be resilient from their continued pursuit of degree attainment, implementation of their strategies, and their use of perceived social supports.

text: Investigating the Social Supports of Successful Māori Undergraduate Appellants at the University of Waikato Educational disparities between Māori and non-Māori tertiary students are evident in regards to participation, retention, and completion rates at secondary and tertiary levels. Instead of focusing on negative statistics, it was of interest to investigate Māori students who had failed sufficient papers to initially be denied re-entry to university study, yet continued to attain their degrees, as a result of a successful appeal. Māori undergraduate students, who had successfully appealed from 2003-2012, were recruited for my research. The availability and utilisation of social supports were investigated, along with the decision to make an appeal, the role of cultural expectations, and barriers experienced by participants. A mixed method approach was utilised in this research through use of an adapted overarching Kaupapa Māori framework, statistical analysis, and 13 interviews. My research found that social supports were beneficial for participants throughout their appeal, as they provided: emotional, instrumental, appraisal, and informational support. Although the social supports utilised by participants were satisfactory, barriers to accessing formal supports were also found, which included: perceived stigma having failed their papers, pride, as well as being whakamā. The appeal process was a beneficial intervention from the University of Waikato, which provided participants another opportunity to overcome the factors that contributed to their initial failure. Post appeal, participants implemented strategies to address and reduce their factors in order to become academically engaged. Participants were deemed to be resilient from their continued pursuit of degree attainment, implementation of their strategies, and their use of perceived social supports.

year: 2013