title: Interaction of polar and tropical influences in the mid-latitudes of the Southern Hemisphere during the Mi-1 deglaciation

authors: Fox, Beth R.S.

subjects: Science & Technology

abstract: It is well-known from geologic archives that Pleistocene and Holocene climate is characterised by cyclical variation on a wide range of timescales, and that these cycles of variation interact in complex ways. However, it is rarely possible to reconstruct sub-precessional (< 20 kyr) climate variations for periods predating the oldest ice-core records (c. 800 ka). Here we present an investigation of orbital to potentially sub-precessional cyclicity from an annually resolved lake sediment core dated to a 100-kyr period in the earliest Miocene (23.03–22.93 Ma) and spanning a period of major Antarctic deglaciation associated with the second half of the Mi-1 event. Principal component analysis (PCA) of sediment bulk density, magnetic susceptibility (MS), and CIELAB L* and b* with a resolution of ~10 years indicates two major environmental processes governing the physical properties records, which we interpret as changes in wind strength and changes in precipitation. Spectral analysis of the principal components indicates that both processes are strongly influenced by obliquity (41 kyr). We interpret this 41-kyr cycle in wind strength and precipitation as related to the changing position and strength of the Southern Hemisphere westerly winds. Precipitation is also influenced by an 11-kyr cycle. The 11-kyr periodicity is potentially related to orbital cyclicity, representing the equatorial semi-precessional maximum insolation cycle. This semi-precession cycle has been identified in a number of records from the Pleistocene and Holocene and has recently been suggested to indicate that insolation in low-latitude regions may be an important driver of millennial-scale climate response to orbital forcing (Feretti et al., 2015). This is the first time this cycle has been identified in a mid-latitude Southern Hemisphere climate archive, as well as the first identification in pre-Pleistocene records. The 11-kyr cycle appears at around 23.01 Ma, which coincides with the initiation of a major phase of Antarctic deglaciation, and strengthens during the subsequent period of rapid ice decay. This pattern suggests that the westerly winds may have expanded north of 50°S at the height of Mi-1, excluding tropical influence from the Foulden Maar site, and subsequently contracted polewards in tandem with warming deep-sea temperatures and Antarctic deglaciation, allowing the advection of tropical waters further south.

text: Interaction of polar and tropical influences in the mid-latitudes of the Southern Hemisphere during the Mi-1 deglaciation It is well-known from geologic archives that Pleistocene and Holocene climate is characterised by cyclical variation on a wide range of timescales, and that these cycles of variation interact in complex ways. However, it is rarely possible to reconstruct sub-precessional (< 20 kyr) climate variations for periods predating the oldest ice-core records (c. 800 ka). Here we present an investigation of orbital to potentially sub-precessional cyclicity from an annually resolved lake sediment core dated to a 100-kyr period in the earliest Miocene (23.03–22.93 Ma) and spanning a period of major Antarctic deglaciation associated with the second half of the Mi-1 event. Principal component analysis (PCA) of sediment bulk density, magnetic susceptibility (MS), and CIELAB L* and b* with a resolution of ~10 years indicates two major environmental processes governing the physical properties records, which we interpret as changes in wind strength and changes in precipitation. Spectral analysis of the principal components indicates that both processes are strongly influenced by obliquity (41 kyr). We interpret this 41-kyr cycle in wind strength and precipitation as related to the changing position and strength of the Southern Hemisphere westerly winds. Precipitation is also influenced by an 11-kyr cycle. The 11-kyr periodicity is potentially related to orbital cyclicity, representing the equatorial semi-precessional maximum insolation cycle. This semi-precession cycle has been identified in a number of records from the Pleistocene and Holocene and has recently been suggested to indicate that insolation in low-latitude regions may be an important driver of millennial-scale climate response to orbital forcing (Feretti et al., 2015). This is the first time this cycle has been identified in a mid-latitude Southern Hemisphere climate archive, as well as the first identification in pre-Pleistocene records. The 11-kyr cycle appears at around 23.01 Ma, which coincides with the initiation of a major phase of Antarctic deglaciation, and strengthens during the subsequent period of rapid ice decay. This pattern suggests that the westerly winds may have expanded north of 50°S at the height of Mi-1, excluding tropical influence from the Foulden Maar site, and subsequently contracted polewards in tandem with warming deep-sea temperatures and Antarctic deglaciation, allowing the advection of tropical waters further south.

year: 2017

title: How an exchange of perspectives led to tentative ethical guidelines for visual ethnography

authors: Pope, Clive C.

subjects: visual ethics

abstract: Qualitative research, especially visual ethnography, is an iterative not a linear process, replete with good intentions, false starts, mistaken assumptions, miscommunication and a continually revised statement of the problem. That the camera freezes everything and everyone in the frame only complicates ethical considerations. This work, jointly authored by the researcher, the Research Ethics Committee (REC) chair and an informed outsider, walks the reader through the ethical challenges the researcher experienced seeking REC approval to conduct a visual ethnography of a secondary school's rowing event. Eventually, the researcher found the challenges and ambiguities of informed consent indicative of the current issues facing many researchers working with the visual medium. The account fleshes out a procedural ethics and ethics in practice dichotomy and ends with the researcher and REC chair retrospectively contemplating the iterative ethics of visual ethnography. We conclude our conversation by proposing five tentative guidelines for visual ethnography researchers and their research ethics committees.

text: How an exchange of perspectives led to tentative ethical guidelines for visual ethnography Qualitative research, especially visual ethnography, is an iterative not a linear process, replete with good intentions, false starts, mistaken assumptions, miscommunication and a continually revised statement of the problem. That the camera freezes everything and everyone in the frame only complicates ethical considerations. This work, jointly authored by the researcher, the Research Ethics Committee (REC) chair and an informed outsider, walks the reader through the ethical challenges the researcher experienced seeking REC approval to conduct a visual ethnography of a secondary school's rowing event. Eventually, the researcher found the challenges and ambiguities of informed consent indicative of the current issues facing many researchers working with the visual medium. The account fleshes out a procedural ethics and ethics in practice dichotomy and ends with the researcher and REC chair retrospectively contemplating the iterative ethics of visual ethnography. We conclude our conversation by proposing five tentative guidelines for visual ethnography researchers and their research ethics committees.

year: 2010

title: Bilingual/Immersion education: Indicators of good practice

authors: May, Stephen

subjects: Maori

abstract: Based on a review of national and international research on bilingualism and bilingual/immersion education, this report explores effective approaches for bilingual education. While the focus was on Māori-medium education, the indicators of good practice can also be applied to other bilingual contexts in Aotearoa/New Zealand, such as Pasifika bilingual education.

text: Bilingual/Immersion education: Indicators of good practice Based on a review of national and international research on bilingualism and bilingual/immersion education, this report explores effective approaches for bilingual education. While the focus was on Māori-medium education, the indicators of good practice can also be applied to other bilingual contexts in Aotearoa/New Zealand, such as Pasifika bilingual education.

year: 2004