AGU Meetings Research Articles

Diffusive fractionation of volatiles and their isotopes during bubble growth in magmas

Bubbles grow in decompressing magmas by simple expansion and by diffusive supply of volatiles to the bubble/melt interface. The latter phenomenon is of significant geochemical interest because diffusion can fractionate elements and isotopes (or isotopologues) of dissolved components. This raises the possibility that the character of volatile components in bubbles may not reflect that of volatiles dissolved in the host melt over the lifetime of a bubble—even in the absence of equilibrium vapor/melt isotopic fractionation. Recent experiments have confirmed the existence of an isotope mass effect on diffusion of the volatile element Cl in silicate melt [Fortin et al. (Isotopic fractionation of chlorine during chemical diffusion in a dacitic melt and its implications for isotope behavior during bubble growth (abstract), 2016 Fall AGU Meeting, 2016)], so there is a clear need to understand the efficacy of diffusive fractionation during bubble growth. In this study, numerical models of diffusion and mass redistribution during bubble growth were implemented for both “passive” volatiles—those whose concentrations are generally well below saturation levels—and “active” volatiles such as CO2 and H2O, whose elevated concentrations and limited solubilities are the cause of bubble nucleation and growth. Both diffusive and convective bubble-growth scenarios were explored. The magnitude of the isotope mass effect on passive volatiles partitioned into bubbles growing at a constant rate R in a static system depends upon R/DL, Kd and DH/DL (Kd = bubble/melt partition coefficient; DH/DL = diffusivity ratio of the heavy and light isotopes). During convective bubble growth, the presence of a discrete (physical) melt boundary layer against the growing bubble (of width xBL) simplifies outcomes because it leads to the quick onset of steady-state fractionation during growth, the magnitude of which depends mainly upon R∙xBL/DL and DH/DL (bubble/melt fractionation is maximized at R∙xBL/DL ≈0.1). Constant R is unrealistic for most real systems, so other scenarios were explored by including the solubility and EOS of an “active” volatile (e.g., CO2) in the numerical simulations. For plausible decompression paths, R increases exponentially with time—leading, potentially, to larger isotopic fractionation of species partitioned into the growing bubble. For volatile species whose isotope mass effects on diffusion have been measured (Cl, Li), predicted isotope fractionation in the exsolved vapor can be as large as −4‰ for Cl and −25‰ for Li.

Charting the Future for AGU's Meetings Program

As Earth and space scientists' needs and ways of interacting change, the American Geophysical Union is developing an improved strategy and vision for the attendee experience at AGU meetings.

From Europe to the United States, Rousseau Takes on the Fall Meeting

Denis‐Didier Rousseau smiles shyly when discussing his new role as the chair of AGU's Fall Meeting Program Committee. “I'm not used to giving interviews,” he says. Nonetheless, he becomes very passionate as he begins to talk about his views on transdisciplinary science and its role in AGU meetings, on including more young scientists in planning meetings, and on the importance of virtual meetings. Rousseau, who is currently a visiting professor at Columbia University, sat with Eos to share his excitement about working with AGU.

Be a Part of AGU in 2014

As the end of the year approaches, remember the many reasons to renew your AGU membership dues for 2014: As an AGU member, you can participate in AGU meetings at special member rates, access Eos, enjoy a 35% discount off the list price of AGU and Wiley books, and be recognized for your work (and recognize others) through AGU's honors and recognition programs.

Notification of Upcoming AGU Council Meeting

The AGU Council will meet on Sunday, 8 December 2013, beginning at 8:30 A.M., at the InterContinental Hotel in San Francisco, Calif. The meeting, which is open to all AGU members, will include discussions about strategies for AGU publishing and meetings, science‐related policies, and changes to the AGU bylaws.

Planning for 2012 AGU Fall Meeting

The Fall Meeting is AGU's flagship meeting and is the largest Earth and space sciences meeting in the world. The high quality of this meeting is due to the joint efforts of the Fall Meeting Program Committee, the professional AGU meetings staff, AGU members who serve as session chairs, and AGU members who submit abstracts and attend the meeting. The 2011 Fall Meeting was attended by more than 21,000 people, including 30% from outside the United States. To maintain the high quality of AGU science and the reputation of AGU for excellence in meetings, the AGU Meetings Committee has finalized the 2012 schedule.

…Where We Are Headed

This is the second of a two-part series marking the transition from Libarkin to St. John as Editor-in-Chief of the Journal of Geoscience Education. As we write this editorial the Fall Semester has come to a close; term papers and exams have been graded, research has been presented at the fall GSA and AGU meetings, and we can take a short break to enjoy the holidays. The transition to a new academic term coincides with two transitions for the Journal of Geoscience Education: journal editorship and publisher. The purpose of JGE - that the journal is a forum for communication among scholars working on cutting-edge questions about teaching learning and cognition in the geosciences - remains unchanged and serves to guide short and long-term strategic editorial, production, and publication decisions. We envision JGE to be the venue of choice for publishing intellectually-stimulating, peer-reviewed articles relevant to the academic geoscience community. We recognize that our community is diverse and growing internationally; we welcome international colleagues who sit within geography, as well as geoscience departments. Our readership includes both NAGT members and nonmembers, geoscientists doing formal research in teaching and learning, as well as those that use JGE as a resource for improving their own teaching in ???, university, and informal education settings. JGE should be the journal that this community wants to publish in and wants to read. Towards that end, we will continue to facilitate quality and timely peer-review, and encourage new submissions of geosciences education manuscripts and commentaries, as well as ideas for theme issues. Should you have questions about manuscript submissions, or ideas for possible commentary or theme issue topics, we encourage you to contact Kristen St. John, Editor-in-Chief (jge@jmu.edu), and discuss them. Updated instructions for authors can be found both on the JGE website (http://nagt-jge.org/) and on the inside back cover of the print JGE. In addition, we propose that the geosciences education community discuss and adopt a broader definition of scholarship, as fits the importance of the term scholar in JGE's statement purpose. This broader definition should align with the Boyer (1990) model in which scholarship not only encompasses original research, but also embraces the value of looking for connections, building bridges between theory and practice, and communicating one's knowledge effectively to both students and peers (Boyer, 1990, p. 16). We believe this model of scholarship matches well with the JGE publication categories of Research, Curriculum & Instruction, and Commentary. In particular, we encourage all potential authors to consider how their contribution connects theory with practice, to the betterment of geosciences education. We also encourage contributions in geosciences education domains that go beyond the traditional K-16 classroom: for example, those that address geoscience professional development, workshops, informal education, research-driven programmatic changes, and studies of expertise. The current JGE editorial board transition occurred at several levels: as of January 1, 2012, the Editor-in-Chief for JGE is Dr. Kristen St. John. Former Editor-in-Chief, Dr. Julie Libarkin, has agreed to continue contributing to the editorial functions of JGE as an Associate Editor, and is overseeing the compilation and production of an upcoming theme issue on Global Geoscience Education, along with Associate Editor Dr. Chun- Yen Chang, of Taiwan, and Guest Associate Editor Dr. Sharon Locke, of South Africa. We welcome Dr. Dan Dickerson (Old Dominion University), former Associate Editor, as the new Editor for Curriculum and Instruction, and Drs. …

Advances in upscaling of eddy covariance measurements of carbon and water fluxes

Eddy covariance flux towers provide continuous measurements of ecosystem‐level net exchange of carbon, water, energy, and other trace gases between land surface and the atmosphere. The upscaling of flux observations from towers to broad regions provides a new and independent approach for quantifying these fluxes over regions, continents, or the globe. The seven contributions of this special section reflect the most recent advances in the upscaling of fluxes from towers to these broad regions. The section mainly stems from presentations at the recent North American Carbon Program (NACP), FLUXNET, and AGU meetings. These studies focus on different aspects of upscaling: (1) assessing the representativeness of flux networks; (2) upscaling fluxes from towers to broad spatial scales; (3) examining the magnitude, distribution, and interannual variability of fluxes over regions, continents, or the globe; and (4) evaluating the impacts of spatial heterogeneity and parameter variability on flux estimates. Collectively, this special issue provides a timely update on upscaling science and also generates gridded flux data that can be used for model evaluations. Future upscaling studies are expected to advance toward incorporating the impacts of disturbance on ecosystem carbon dynamics, quantifying uncertainties associated with gridded flux estimates, and comparing various upscaling methods and the resulting gridded flux fields.

Outstanding student paper awards

The following members received Outstanding Student Paper Awards at the 2010 AGU Meeting of the Americas, in Foz do Iguaçu, Brazil.

Evolution of the AGU Fall Meeting

The Fall Meeting is AGU's flagship meeting and is the largest Earth and space sciences meeting in the world. The high quality of this meeting is due to the joint efforts of the Fall Meeting Program Committee, the professional AGU meetings staff, AGU members who serve as session chairs, and AGU members who submit abstracts and attend the meeting. The Fall Meeting in 2010 was attended by more than 19,000, including 31% from outside the United States. Attendance at the Fall Meeting has been growing at a steady rate of approximately 6–8% per year over the past decade.

Teachers Explore Earth Science in South America: Rain, Rocks, and Climate: A Geophysical Information for Teachers Workshop; Foz do Iguaçu, Brazil, 8–9 August 2010

Classroom teachers and university professors from two continents joined to learn about “rocks, rain, and climate” in the Geophysical Information for Teachers (GIFT) workshop at the AGU Meeting of the Americas held in Brazil. This was the first GIFT workshop in South America. GIFT workshops have long been part of AGU Fall Meetings in San Francisco, European Geosciences Union Spring Meetings in Vienna, and other AGU conferences. Two Brazilian geoscience professors, Celso Dal Ré Carneiro of State University of Campinas and Nisia Krusche of Federal University of Rio Grande, organized the program, together with a high‐school teacher from the United States, Michael J. Passow of Dwight Morrow High School, Englewood, N.J. Joining the presenters were 15 Brazilian teachers and another teacher from New Jersey.

AGU Blogosphere: A New Community of Earth and Space Science Blogs

Less than a year ago, AGU had yet to explore the world of science blogging. Now AGU not only has three blogs of its own but also has launched the AGU Blogosphere, a network of independent Earth and space science blogs hosted under the Union's umbrella. The new network of blogs, composed of seven external blogs written by scientists and covering topics including planetary exploration, landslides, Washington, D.C.—area geology, volcanoes, climate change, and more, can now be found together with the in‐house blogs at http://blogs.agu.org.It's been a fast, exciting immersion into the blogosphere for AGU. Efforts began with the 2009 Fall Meeting blog, run by AGU staff with the invaluable help of science writing students at University of California, Santa Cruz and New York's Columbia University. This successful experience inspired AGU outreach staff to make a permanent meetings blog, which regularly covers the science presented at AGU meetings.

David J. Hofmann (1937–2009)

David J. Hofmann, a pioneer in stratospheric aerosol and ozone research, passed away in Boulder, Colo., on 11 August 2009. He was 72. Dave, a frequent contributor to AGU publications and meetings, was elected an AGU Fellow in 2006.His long and prolific scientific career was, as he would say, simple in concept: Make a long‐term commitment to specific measurements, pay attention to the details, and focus on the important issues that the measurements raise. This is simple in concept yet challenging to maintain in a world of short‐term contracts and budgets. That Dave sustained and led key measurement programs through 25 years at the University of Wyoming (UW), in Laramie, and 17 years with the U.S. National Oceanic and Atmospheric Administration's (NOAA) Climate Monitoring and Diagnostics Laboratory (CMDL, which became the Global Monitoring Division (GMD) of NOAA's Earth System Research Laboratory) in Boulder, speaks volumes about the scientific and societal benefits that have resulted from his work.

Tomorrow's AGU: Building a Foundation for Good Governance

In May, the AGU Council voted unanimously to create a 16‐member board of directors to oversee the business of the Union, and to expand the Council beyond section leadership to include focus group and committee leaders concentrating on matters of science and related Union activities such as AGU publications, meetings, and awards and honors (see Eos, 90(25), 213, 23 June 2009). This fall, the AGU membership will be asked to vote on these important changes.The Council action followed careful deliberation and reflects the recommendations of the Future Focus Task Force, which was formed to answer the question, “How will AGU need to change the way it does business to achieve its strategic vision and mission and remain a preeminent scientific society?”

No “Student Members”—Only Student Fees

AGU has three classes of individual membership: Members, Fellows, and Honorary Fellows. As you can see, “students” is not a membership class. For almost 50 years, members of AGU who are students have enjoyed much reduced dues and special rates for most AGU publications, meetings, and other services and activities. Throughout those years, AGU has tried to create a welcoming environment for students.Like many members who are now leaders in our community, I joined AGU as a graduate student. We benefited from our generous seniors as we joined the scientific fray at our early meetings and battled our way for recognition. I trust that we have shown the same support for the next generation and that this tradition continues to prosper.

Judy C. Holoviak Receives Edward A. Flinn III Award

Judy C. Holoviak received the Flinn Award at the AGU Meeting of the Americas in 2008. The award honors ‘individuals who personify the Union's motto ‘unselfish cooperation in research’ through their facilitating, coordinating, and implementing activities.”

K.D. Putirka and F.J. Tepley (editors). Minerals, Inclusions and Volcanic Processes. Reviews in Mineralogy and Geochemistry Series, Mineralogical Society of America, Chantilly, Virginia and Geochemical Society of America, Saint Louis, Missouri, USA. 2008, 69, 674 pp. Price $40, ISBN: 978-0-939950-83-6.

This RiMG volume is an impressive text that formed the basis for a MSA Short Course, held in San Francisco prior to the Fall AGU Meeting in December 2008, which achieved record attendance figures. The MSA website provides links to Excel spreadsheets that accompany several of the chapters. The text divides loosely into four sections: (1) thermobarometry and kinetics, including methods for inferring magmatic conditions, (2) melt inclusions and volatile abundances, (3) isotopic systems, and (4) textural studies and micro-geochemistry of zoned minerals. Chapter 2 (Julia Hammer) addresses the kinetics of crystallization. The chapter gives an overview of classical nucleation theory, reviews experiments on cooling of basalts and decompression of felsic magmas, and discusses methods used to quantify the textures produced in such experiments. In Chapter 3, Keith Putirka considers thermobarometry for volcanic systems, focusing mainly on well calibrated, …

Editorial: Welcome from the new Editors

[1] Paleoceanography occupies a central role for publications on how the oceans have evolved over time. On 1 January 2006 we officially began 4-year terms as the new Editors of this journal. Following tradition, we share some opening commentary. [2] Our journal presently sits at the cusp of our discipline for two reasons: great editing over the past 4 years and a steady stream of strong papers. The journal was in a difficult situation several years ago, with long turnaround times between submission and publication and a mostly hard copy format. During their editorial terms, Lisa Sloan and Larry Peterson have expertly guided the journal, which has experienced a significant reduction in the handling time of manuscripts and a very successful transition to full electronic format. Along with their active nurturing of submissions and an emphasis on a constructive and fair review process the journal has received and published a series of exciting and incisive contributions. Once again, Paleoceanography resides as the flagship journal for our discipline. On behalf of all who read and usePaleoceanography, we thank Lisa and Larry for the energy and effort they devoted as Editors. Of course, a peer-reviewed scientific journal can only remain top-notchwith outstanding submissions, excellent refereeing, and an active audience. We also thank you. [3] As the new Editors, our first aim is to maintain the high standards set by Lisa and Larry. We will strive for outstanding science, a rapid turnaround of papers, and a fair and constructive reviewing process. Like our predecessors, we also take a broad view of Paleoceanography. Our discipline naturally spans incredible scientific diversity and invites links to other research fields, such as oceanography, geology, climatology, geochemistry, biochemistry, physical geography, paleontology, and more. We see these attributes as a key to the past and future strength of our journal, and we encourage submissions that cover a wide range of timescales and topics. As a general guideline, Paleoceanography should be a choice for excellent work that has been or could be presented in most ‘‘Paleoceanography and Paleoclimatology’’ (PP) sessions at annual AGU meetings. We stress, though, that the exact content of our journal depends on you. [4] Although we are generally pleased with Paleoceanography, we will strive to make a few changes that reflect the nature of our discipline. As highlighted at the 2005 American Geophysical Union Fall Meeting by Jim Kennett, the founder and first Editor of our journal, the focus of research in our discipline has shifted considerably over the past 50 years; paleoceanography has now matured into the cornerstone for understanding and constraining global processes in the time domain (J. P. Kennett, Paleoceanography and beyond: Changing perspectives over more than four decades, Eos Transactions AGU, 86(52), Fall Meeting Supplement, Abstract PP24A-08, 2005). One consequence of this progression is the increasing need to truly integrate location-specific data with large-scale models for mass and heat transfer. Too often, interpretations of data are made without considering a larger modeling context (Is the interpretation plausible? How might the interpretation be used?), and models are presented without considering the full range of available data (Does the model explain all relevant observations? What data can be generated to test the model?). We will make a concerted effort to improve data-model interaction. [5] We will also encourage open discussion about the quantification and robustness of results. Paleoceanography has long emphasized innovative studies that present new and exciting interpretations, concepts, and proxies. We feel that, in a specialized journal with relatively generous page limits, it should also be the norm to include discussion about key assumptions, process representations, potential problems, uncertainties, and alternative explanations. Such discussions, applicable to analytical and numerical studies, trigger new developments that improve our reconstructions and make our efforts more useful to the wider community. We are fully aware that well-defined qualitative observations can offer critical constraints, even if they cannot be easily incorporated into quantitative models. In these cases the robustness of the interpretations should still be transparently evaluated. [6] In addition, we will institute a few changes to the journal format. First, we will resurrect Paleoceanography Currents, the section for short, provocative papers, ideally 5 pages or less when printed. Right now, Paleoceanography does not embrace these papers so they are being published elsewhere. We want great short papers on topics relevant to our discipline published in Paleoceanography. [7] Second, we will limit all articles to the equivalent of 16 printed pages, including text, figures, tables and references. Frankly, we find very few colleagues interested PALEOCEANOGRAPHY, VOL. 21, PA1000, doi:10.1029/2006PA001272, 2006

Keeping pseudoscience out of AGU meetings

I found the editorial, “Speaking Up For Science” (Eos, 86,(24), 14 June 2005, p. 225) disturbing, but not for the reasons you intended. The Smithsonian made a mistake, but nowhere do you discuss its efforts to correct that.More troublesome to me as a member of AGU is the blatant hypocrisy contained in the editorial. How many posters or presentations have been made at AGU meetings in the last 10–20 years that support creationism, intelligent design, or other forms of pseudo‐science, such as the so‐called “face” on Mars?

A challenge to the membership

Students are key to the future of the Earth and space sciences and to the vitality of our global AGU community. More than 7300 students are now members of the Union (17% of the total membership); of these, 30% live outside the U.S. Equally important, student attendance at AGU's major meetings has been steadily climbing. In 2004, a remarkable 25% of the registrants for major AGU meetings were students.An increasing number of qualified students apply for travel grants to attend these meetings. Yet, only 5% (see Figure 1) receive these modest grants of $300–$650 because Union resources have not kept pace with demand. More students need financial aid, and our charge is to “find” the funds to help them.