Volcanic activity and global change: probable short-term and possible long-term linkages

Article reviews annual to decadal climate response to volcanism; long-term climatic response to volcanism; and recent results from ocean drilling in the North Pacific

Triggering global climate transitions through volcanic eruptions

A coupled climate model with idealized representations of atmosphere, ocean, sea ice, and land is used to investigate transitions between global climate equilibria. The model supports the presence of climates with limited ice cover (Warm), a continuum of climates in which sea ice extends down into the midlatitudes and the tropics (Cold), together with a completely ice-covered earth (Snowball). Transitions between these states are triggered through volcanic eruptions, where the radiative effect of stratospheric sulfur emissions is idealized as a 1-yr impulse reduction in incoming solar radiation. Snowball transitions starting from the Cold state are more favorable than from the Warm state, because less energy must be extracted from the system. However, even when starting from a Cold climate, Toba-like volcanic events (cooling of order 2100 W m22) must be sustained continuously for several decades to glaciate the entire planet. When the deep ocean is involved, the volcanic response is characterized by relaxation time scales spanning hundreds to thousands of years. If the interval between successive eruptions is significantly shorter (years to decades) than the ocean’s characteristic time scales, the cumulative cooling can build over time and initiate a state transition. The model exhibits a single hysteresis loop that connects all three climate equilibria. When starting from a Snowball, the model cannot access the Cold branch without first transitioning to an ice-free climate and completing the hysteresis loop. By contrast, a Cold state, when warmed, transitions to the Warm equilibrium without any hysteresis

Lead isotope provinciality of central North Pacific Deep Water over the Cenozoic

Understanding the pre-anthropogenic Pb cycle of central North Pacific deep water has attracted a lot of attention in recent years, partly because of its unique geographical location in that it is a remote gyre system characterized by high dust fluxes and sluggish overturning circulation. However, the factors controlling Pb isotope evolution in this area over the Cenozoic are still controversial and various mechanisms have been proposed in previous studies. Here we report new Pb and Nd isotope time series of four ferromanganese crusts (two from the western Pacific near the Mariana arc and the other two from the central Pacific). Together with previously published records, we discuss for the first time the significance of a persistent and systematic Pb isotopic provinciality recorded by central North Pacific crusts over the Cenozoic. We propose that globally well mixed stratosphere volcanic aerosols could contribute Pb but have not been the major factors controlling the Pb isotope distribution in the central North Pacific over time. Island arc input (and probably enhanced hydrothermal input between about 45 and 20 Ma) likely controlled the Pb isotope provinciality and evolution prior to ~20 Ma, when coeval Pb isotope records in different crusts showed large differences and atmospheric silicate dust flux was extremely low. After the Eocene, in particular after 20 Ma, Asian dust input has become an isotopically resolvable source, while island arc-derived Pb has remained important to balance the dust input and to produce the observed Pb isotope distribution in the central North Pacific during this period

Cenozoic evolution of Asian climate and sources of Pacific seawater Pb and Nd derived from eolian dust of sediment core LL44‐GPC3

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95692/1/palo954.pd

Tephra without borders: Far-reaching clues into past explosive eruptions

This review is intended to highlight recent exciting advances in the study of distal (>100 km from the source) tephra and cryptotephra deposits and their potential application for volcanology. Geochemical correlations of tephra between proximal and distal locations have extended the geographical distribution of tephra over tens of millions square kilometers. Such correlations embark on the potential to reappraise volume and magnitude estimates of known eruptions. Cryptotephra investigations in marine, lake and ice-core records also give rise to continuous chronicles of large explosive eruptions many of which were hitherto unknown. Tephra preservation within distal ice sheets and varved lake sediments permit precise dating of parent eruptions and provide new insight into the frequency of eruptions. Recent advances in analytical methods permit an examination of magmatic processes and the evolution of the whole volcanic belts at distances of hundreds and thousands of kilometers from source. Distal tephrochronology has much to offer volcanology and has the potential to significantly contribute to our understanding of sizes, recurrence intervals and geochemical make-up of the large explosive eruptions

“Dementia” and “Good Dementia Care” in Denmark: Implications for Danish-Chinese Dementia Care Collaboration

Thesis (Master's)--University of Washington, 2020As countries around the world grapple with how to provide effective dementia care to aging citizens, there is tremendous opportunity for both constructive cross-cultural collaboration and ineffective attempts at transplanting care models into cultural contexts where they do not meet local needs. In response to increasing interest and investment in Danish-Chinese elder care and dementia care collaborations, this study draws on qualitative data collected in Denmark and long-term ethnographic research in China to explore the limitations and potentials of these collaborations. Specifically, this study explores (1) Danish understandings of what dementia is and (2) how understandings of “good dementia care” are influenced by those conceptions of dementia. In Denmark, semi-structured interviews (n=13) and direct, naturalistic observations at two care sites (n=3) were carried out in the Fall of 2016. Analysis in this project also draws on 16 months of ethnographic fieldwork carried out in Sichuan, China primarily in 2017-2018. Results of this study revealed that participants tended to understand “dementia” in terms of how it was experienced by individuals, how it fit into individuals’ existing relationships to the Danish state, and as a condition with shifting associations to stigma. “Good dementia care” was described in terms of its complexity, the way it required caregivers to use new forms of communication, its relationship to specialized caregiving spaces and institutional environments, its reliance on a “professional” workforce, and the idea that “good dementia care” is an ideal that is limited by real world constraints in practice. Differences in expectations of family member involvement in dementia care sites, in volunteerism, and in political economic activism among older adults were identified as potentially limiting factors in successful collaborations. Infrastructure and systems support were also found to be potential barriers for partnerships. In contrast, collaborations around caring for violent or difficult residents, addressing the limitations of a person-centered care approach, and finding ways to strengthen non-state-provided dementia care systems and support family caregivers offered more promise. This study raises important issues for consideration when evaluating or developing Danish-Chinese elder care collaborations and suggests developing new care frameworks, engaging and supporting family caregivers, and finding new ways to manage difficult or violent residents offer especially promising areas for such partnerships

Instituting Care: A Dementia Unit in Mainland China

Thesis (Ph.D.)--University of Washington, 2021As China’s population ages, its government and medical marketplace are developing new forms of institutional, non-family-based eldercare and dementia care. This dissertation explores one such site, providing an organizational ethnography of a private dementia care unit in Sichuan, China. Conclusions drawn in this dissertation are based upon 16 months of ethnographic fieldwork carried out in Sichuan between 2015 and 2019 (primarily during the 2017-2018 academic year), including observations and semi-structured and/or unstructured interviews with dementia care staff, administrators, residents, family members, and scholars. This dissertation centers on interactions between different groups of participants within the dementia care unit – residents, family members, staff and administrators at different levels, and the author – to explore how these groups ultimately come together to shape care practices. This dissertation considers how institutional care fundamentally operates as care for institutions, where interpersonal care practices must also be understood in relation to the tremendous investments of time, attention, and resources needed to create and sustain institutional care settings. This approach shows the primary research site as a flexible institution – a place where there are simultaneously institutional norms and standards shaping what is possible for the care and labor environments within its walls and a constant negotiating and stretching of those institutional boundaries. This dissertation also contributes to discussions around what “care” or “good care” means in practice, and how relationality shapes dementia care not only in interpersonal relationships between caregivers and care receivers, but also in terms of relationality among caregiving staff within an institutional setting. In exploring complicated care practices such as the use of physical restraints, this research considers what such practices reveal about how needs are understood for people living with dementia, their families, the staff who care for them, and the institutions where they live

The plio-pleistocene history of explosive volcanic activity in north Pacific Island arcs and possible links to regional and global climate change.

Deep-sea sediment recovered by Ocean Drilling Project (ODP) Leg 145 contain the best record yet of explosive volcanic activity over a wide geographical region as well as a record of an intensification of Northern Hemisphere glaciation that occurred at 2.65 Ma. Comparison of this ash record with other ODP sites and with terrestrial records demonstrates the reliability of the ash layer stratigraphy and that this ash record is appropriate to use in an investigation of the effects of explosive, silicic, volcanism on climate. The glacial intensification is recorded in the sediment as an abrupt increase in terrigenous clastic sediment and ice-rafted debris (IRD). The number and thickness of volcanic ash layers increases abruptly in the sediment at the same time. Magnetic susceptibility records show that the climate change occurred rapidly, within 1000--2000 years, too quickly to be a response to tectonic or orbital forcing. The rapid, synchronous, basin-wide climate change suggests that the climate forcing mechanism operated over decades to millennia and was hemispherical in extent. The synchronous increase in volcanism suggests that explosive eruptions may have been the trigger of the glacial onset. Ash layers in marine sediment are often the best preserved record of the explosive history of an arc, because deep-sea sediments are less susceptible to erosion. Volcanic ash layers in deep-sea sediments of the northern Pacific Ocean provide a record of the episodic explosive volcanism in the Kamchatka and Aleutian volcanic arcs, including a major episode that began about 2.65 Ma at both arcs. Mass-accumulation rates (MAR) of volcanic glass and IRD were calculated as a way to determine the stratigraphic relationship between the ash and the IRD. Volcanic glass is used as a proxy for explosive volcanic eruptions and IRD is used as a proxy for glaciation. MAR of both the glass and IRD show a five- to ten-fold increase at 2.65 Ma, with the flux of the glass increasing just prior to the flux of the IRD, again suggesting that explosive eruptions may have been the trigger for the glaciation.Ph.D.Earth SciencesGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131980/2/9938516.pd

Accumulation rates of volcanic glass and ice-rafted debris in sediments of the North Pacific Ocean

Mass accumulation rates (MAR) of different components of North Pacific deep-sea sediment provide detailed information about the timing of the onset of major Northern Hemisphere glaciation that occurred at 2.65 Ma. An increase in explosive volcanism in the Kamchatka-Kurile and Aleutian arcs occured at this same time, suggesting a link between volcanism and glaciation. Sediments recovered by piston-coring techniques during ODP Leg 145 provide a unique opportunity to undertake a detailed test of this possibility. Here we use volcanic glass as a proxy for explosive volcanism and ice-rafted debris (IRD) as a proxy for glaciation. The MAR of both glass and IRD increase markedly at 2.65 Ma. Further, the flux of the volcanic glass increased just prior the flix of ice-radted material, suggesting that the cooling resulting from explosive volcanic eruptions may have been the ultimate trigger for the mid-Pliocene glacial intensification