55 research outputs found
Episode 091 - Jesse Stommel
No full textJesse Stommel is an author, speaker, and teacher with a focus on education, critical digital pedagogy, and documentary film. He’s the co-founder of the Digital Pedagogy Lab, a fantastic professional development workshop for those interested in critical digital pedagogy. He’s the co-founder of Hybrid Pedagogy, the journal of critical digital pedagogy. And he’s the co-author of An Urgency of Teachers: The Work of Critical Digital Pedagogy.
Jesse is an incredible thoughtful and powerful voice in higher education. His work and writings have influenced so many educators, and we are thrilled to have him on the podcast
Variability of water masses and circulation in the subtropical North Atlantic
No full textObservations of interannual variability in 18 Water (Talley and Raymer 1982) and Gulf Stream transport (Worthington 1977) motivate an ocean model sensitivity study. The North Atlantic circulation is simulated with a three-dimensional isopycnic coordinate GCM. Idealized anomalous buoyancy-forcing fields (associated without breaks of cold, dry continental air over the Gulf Stream/Sargasso Sea region) are constructed. In a series of sensitivity experiments, wintertime buoyancy loss over the Gulf Stream and Sargasso Sea is thus increased to varying degrees, with anomalous ocean-to-atmosphere buoyancy fluxes of up to double climatological values. Under excess buoyancy loss, winter mixed layer depths increase, and a greater volume of model 18 Water is formed. End-of-winter mixed layer density also increases, leading to the formation of a denser variety of 18 Water. The anomalous 18 Water recirculates around the Sargasso Sea as a signal of low potential vorticity, which spreads out and weakens on a decadal timescale. Strengthened horizontal pressure gradients in the vicinity of the anomalous 18 Water drive intensified baroclinic transports at the "immediate" end of winter (in March), after which a full-depth barotropic intensification of the Gulf Stream develops. Strongest intensification occurs in May, when the Gulf Stream barotropic transport is increased locally by up to 10 Sv. The anomalous transports which account for barotropic intensification are confined to deep and abyssal layers of the model. Where the associated anomalous bottom currents traverse isobaths, "extra" bottom pressure torque (BPT) is invoked. Ananomalous BPT term in the barotropic vorticity balance may therefore account for the intensification. Computed from the model fields of density and sea surface height, such a term does appear to produce the extra negative vorticity associated with anticyclogenic intensification. It is concluded that wintertime excess buoyancy loss drives a springtime barotropic response of the subtropical gyre, through BPT, due to "JEBAR" (the Joint Effect of Baroclinicity And Relief). The Gulf Stream intensification decreases after May as lateral eddy mixing weakens anomalous cross-stream pressure gradients. This eddy mixing is parameterized in the model by a layer thickness diffusion velocity, ud, nominally chosen to be 1.0 cm s-1. Further experiments establish the sensitivity of intensification strength to the choice of ud. With ud = 0.1 cm s-1 (weak thickness diffusion), the intensification is increased by ~50%, while, for ud - 10 cm s-1 (strong thickness diffusion), the intensification is roughly halved. These further sensitivity experiments also reveal the varying degrees to which the model subtropical gyre can be dominated by diffusive eddy mixing (Rhines and Young 1982a, 1982b) or adiabatic (nondiffusive) ventilation of the thermocline (Luyten, Pedlosky and Stommel 1983). Recent (1980-97) interannual variability in the formation and recirculation of 18 Water, and other water masses, is deduced from observed surface heat and freshwater fluxes. Interannual variations in the strength of 18 Water renewal (thus deduced) and a wintertime index of the North Atlantic Oscillation (NAO) are found to be strongly anticorrelated (with a correlation coefficient of -0.70, statistically significant at a 99% confidence level). A further sensitivity experiment establishes that anomalous wind forcing, characteristic of a minimum phase in the NAO, does not intensify the GulfStream in the manner of excess cooling. It is concluded that 18 Water is more strongly renewed, with accompanying Gulf Stream intensification, under NAO-minimum buoyancy forcing
Die Grenzboten : Zeitschrift für Politik, Literatur und Kunst / Johann Maria Hildebrandt.
No full text
Stommel’s box model of thermohaline circulation revisited - the role of mechanical energy supporting mixing and the wind-driven gyration
No full textAuthor Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 909–917, doi:10.1175/2007JPO3535.1.The classical two-box model of Stommel is extended in two directions: replacing the buoyancy constraint with an energy constraint and including the wind-driven gyre. Stommel postulated a buoyancy constraint for the thermohaline circulation, and his basic idea has evolved into the dominating theory of thermohaline circulation; however, recently, it is argued that the thermohaline circulation is maintained by mechanical energy from wind stress and tides. The major difference between these two types of models is the bifurcation structure: the Stommel-like model has two thermal modes (one stable and another one unstable) and one stable haline mode, whereas the energy-constraint model has one stable thermal mode and two saline modes (one stable and another one unstable). Adding the wind-driven gyre changes the threshold value of thermohaline bifurcation greatly; thus, the inclusion of the wind-driven gyre is a vital step in completely modeling the physical processes related to thermohaline circulation.YPG was supported by the National
Science Foundation of China (NSFC, 40676022),
the National Basic Research Program of China
(2006CB403605), and the Guangdong Natural Science
Foundation (5003672). RXH was supported by the National
Oceanic and Atmospheric Administration
through CICOR Cooperative Agreement NA17RJ1223
to the Woods Hole Oceanographic Institution
The use of conversation analysis to study social accessibility of an online support group on eating disorders
No full textWe conducted a conversation analysis of 21 threads initiated by newcomers of an online support group (OSG) on eating disorders, to examine the discursive process of entering such a group. The analysis revealed three important issues. First, many newcomers articulate that the step to join the group is extremely difficult. Second, a presentation of the self in terms of a diagnosis works as a legitimization for joining the forum. The data suggest that participants who do not fulfil the conditions for such a legitimization do not join the forum. Third, the option of acquiring a serious symptom as a solution to the legitimization problem is offered by one of the regular members. Hence, the newcomers' discourse reveals issues relevant to the accessibility for undiagnosed sufferers. We discuss these findings theoretically as a phenomenon of self-presentation in relation to community norms. The analysis generates the hypothesis that newcomers are confronted with implicit norms regarding membership legitimacy that they should obey in their self-presentation, although they may not be ready yet to actually do so. OSGs should find strategies to facilitate various possibilities for newcomers to present themselves to the group while becoming a member. © The Author(s) 2011
A Revised Model of the Ocean’s Meridional Overturning Circulation
No full textThis work explores the density-driven overturning circulation of the ocean using a process-oriented three-dimensional hydrodynamic model with a free sea surface. As expected, dense-water formation in polar regions creates a deep western boundary current (DWBC) spreading southward along the continental slope. Near the equator, the DWBC releases its water eastward into the ambient ocean to form a large upwelling zone. This upwelling is coupled with a slow westward surface recirculation feeding into a swift surface return flow along the western boundary that closes the mass budget. This recirculation pattern, which is fundamentally different to the Stommel–Arons model, is a consequence of geostrophic adjustment to anomalies of the surface pressure field that form under the influence of both coastal and equatorial Kelvin waves and Rossby waves. Based on the findings, the author presents a revised model of the ocean’s meridional overturning circulation to supersede earlier, incorrect suggestions
Complaining and the management of “face” in online counseling
No full textIn this article, we analyze how clients in online counseling by email do complaining. Complaining is a "face-threatening act" and can jeopardize the relationship between interlocutors. In online health interventions, we see high dropout rates. We suggest that because the interaction between client and counselor is at the basis of counseling, it is important to understand how a communicative act (e.g., a complaint) that signals potential dropout is constructed sequentially. Based on a corpus of 20 email exchanges, we illustrate how clients constructed complaints over several sentences and sometimes various emails, and how they designed the complaints to minimize threat to the counselor's face. Counselors, in their responses, used various strategies to manage face threats. We show how complaints were mitigated to protect the counseling relationship and suggest that this is useful knowledge for health professionals. © The Author(s) 2014
When technological affordances meet interactional norms : The value of pre-screening in online chat counseling
No full textWe present a conversation analysis of openings sequences of online text-based chat counseling. Particular about this chat counseling is that the clients made available their help question through pre-screening. The data consisted of 40 chat sessions with pre-screening and 34 sessions without pre-screening from the Dutch alcohol and drugs chat service. In the chat sessions with pre-screening, the participants displayed accountability with regard to the norms relevant to pre-given information, which took up space and time and frequently involved interactional misalignment. In chat sessions without pre-screening of the question, the openings followed a more fluent interactional course. We discuss how affordances of digital communication media may work as constraints when the participants orient to interactional norms known from other, offline environments.</p
Model output used in the manuscript "Micro and macro parametric uncertainty in climate change prediction: a large ensemble perspective"
No full textThis *.zip file contains the model output from ensemble simulations for the Lorenz 84-Stommel 61 model (hereafter L84-S61; Van Veen et al, 2001; Daron and Stainforth, 2013). To run these simulations, we used the E-forth ensemble generator (de Melo Viríssimo and Stainforth, in preparation), which is a MATLAB toolbox that allows for large ensembles of low-dimensional dynamical systems to be run and studied in a systematic way (de Melo Viríssimo and Stainforth, 2023). These model outputs are presented and discussed in the Preprint "Micro and macro parametric uncertainty in climate change prediction: a large ensemble perspective". The manuscript describes the experiments performed, the parameter values used and the modifications done to the original L84-S61 model. For this matter, we also refer you to Daron and Stainforth (2013) and de Melo Viríssimo et al. (2024). All files uploaded were generated from simulations run by the lead author. For specific information about each file uploaded, please refer to the README file. The details of each experiment are also presented in the supplementary materials of the preprint above. If you have any questions, please feel free to contact me.
References: Van Veen et al. (2001): https://onlinelibrary.wiley.com/doi/abs/10.1034/j.1600-0870.2001.00241.x Daron and Stainforth (2013): https://dx.doi.org/10.1088/1748-9326/8/3/034021 de Melo Viríssimo and Stainforth (2023): https://doi.org/10.5194/egusphere-egu23-14755 de Melo Viríssimo et al. (2024): https://doi.org/10.1063/5.0180870 de Melo Viríssimo and Stainforth (in preparation): to appea
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