Goldschmidt 2015

Goldschmidt 2015 
Dates: 16-21 August 2015 
Location: Prague, Czech Republic

For further information: http://goldschmidt.info/2015/index

GEOTRACES sessions:

Theme 2: Ocean Geochemistry. Present Conditions and Past Variation: fluxes, reservoirs and processes

Co-ordinators:
Geraldine Sarthou (Brest University, France)
Andrew Bowie (University of Tasmania)

Team members:
Katherine Barbeau (Scripps, USA), Kristen Buck (Univ South Florida, USA), Zanna Chase (Institute for Marine and Antarctic Studies, Austra), Rob Middag (Univ Otago, New Zealand), James Moffett (Univ. Southern Carolina, USA)

Our understanding of the functioning of the Earth system requires a knowledge of the broad spectrum of processes that influence chemical composition, cycling and transfer of elements in the oceans and their interactions with the atmosphere, land and crust. Ocean geochemistry aims to link and integrate studies of the modern oceans with work using proxies to define how ocean chemistry and the coupled ocean-atmospheric system has changed through the past on a number of different timescales. Critical to these efforts are considerations of how ocean chemistry influences and responds to biological activity and the impact of anthropogenic activity on the marine environment, with important outcomes to issues as diverse as climate change and the capacity of the oceans to remove toxic metals. This theme welcomes submissions in a wide range of marine research areas, including contemporary ocean composition and speciation, transport processes in the ocean, air-sea gas exchange, paleo-oceanography, to the evolution of the ocean due to environmental forcings such as acidity, temperature, and oxygen.

Theme 2 sessions descriptions (complete abstracts of all presentations are available at Goldschmidt site, please click on the links below to access the Goldschmidt webpage for each session):

02a: Trace Metals in the Ocean: Distributions, Isotopic Variation and Speciation
Session Convenors: Katherine Barbeau (UC San Diego, Scripps Institution of Oceanography, USA), Andrew Bowie (University of Tasmania), Kristen Buck (University of South Florida, College of Marine Science, USA), Rob Middag (Univ Otago, New Zealand), Christopher Pearce (National Oceanography Centre), Phil Pogge von Strandmann (Earth Sciences, University College London, UK), Géraldine Sarthou (LEMAR CNRS, Brest, France).

Abstract: Many trace elements are critical for marine life. However, the mechanisms controlling how these metals influence the functioning of ocean ecosystems remain elusive. In conjunction with changes in concentration and speciation, variations in metal stable isotopes provide enhanced discriminatory power for constraining these biogeochemical cycles, as each process imparts a unique isotopic signature to the water column. The GEOTRACES program, which aims to map the world’s oceans for trace elements and isotopes with unprecedented resolution, combined with a growing inventory of metal isotope systems, has facilitated rapid progress in this area. This session seeks to bring together scientists from recent oceanographic cruises to integrate results within and between ocean basins, providing new insights on the behaviour of trace metals in the global ocean. We invite abstracts on all aspects of oceanic trace metal distributions and speciation, as well as their isotopes (both radiogenic and stable), including their application to reconstructing past marine processes such as ocean circulation, redox conditions and hydrothermal activity. We also encourage inter-calibration studies, development of new analytical techniques and modelling work.

Keynote speaker: Gideon Henderson (University of Oxford, UK)
Invited speakers: François Lacan (LEGOS CNRS, Toulouse, France)

02b: Radionuclides in the Ocean
Session Convenors: Bob Anderson (Lamont-Doherty Earth Observatory, USA), Ken Buesseler (Woods Hole Oceanographic Institution, USA), Pere Masque (Universitat Autònoma de Barcelona)

Abstract: Natural uranium/thorium series, cosmogenic and anthropogenic radionuclides, with their in-built “clocks” and contrasting geochemical properties and biological affinities, have been instrumental for understanding and quantifying many important questions in oceanographic research. Examples include circulation and mixing of water masses, particle cycling, sediment and coral dating, and fluxes at ocean boundaries, amongst many other processes.  The Fukushima Dai-ichi disaster has also recently heightened public and policy concerns related to the human health effects of radioactivity attributable to external exposure from ocean contact and internal exposure from seafood consumption. Yet knowledge gaps remain regarding the spatial and depth distributions and the temporal evolution of many radionuclides of importance to both oceanographic and human health issues. This session will bring together scientists that are using radionuclides to better understand processes in the oceans through field based studies, such as GEOTRACES, laboratory experiments, and modeling approaches.  This session will also accept presentations on advances in our methods for sampling and the analysis of ocean radionuclides.  More broadly, the session will consider presentations on new tools to enhance public understanding of radioactivity, and the education and training of the next generation of marine radiochemists.

Invited speakers: Valentí Rodellas (Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Spain), John Smith (Bedford Institute of Oceanography, Canada), Walter Geibert (Alfred Wegener Institute, Germany)

02c: Past Changes in Ocean Biogeochemistry and Circulation and their Interaction with Climate
Session Convenors: Zanna Chase (Institute for Marine and Antarctic Studies, Australia), Martin Frank (GEOMAR Helmholtz centre for ocean research Kiel, Germany), Norbert Frank (University of Heidelberg, Germany), Katharina Pahnke (ICBM and MPI for Marine Microbiology, Germany), Laetitia Pichevin (University of Edinburgh, UK), Laura Robinson (University of Bristol, UK), Tina van de Flierdt (Imperial College London, UK), Kazuyo Tachikawa (Cerege, CNRS, France)

Abstract: Ocean biogeochemistry and circulation have influenced or even controlled climate on different time scales. Given that historical observations of ocean properties are restricted to the last ~100 years, it is essential to reconstruct their involvement in Earth’s climate prior to human induced changes.
Trace-element and isotope geochemistry offer powerful tools to constrain such changes. For this session we invite contributions addressing past ocean circulation, productivity and nutrient cycling based on stable, radiogenic, or radioactive isotope signatures or other geochemical tracers from millennial to million year time-scales from the recent past to deep time, from bulk sediment to deep-sea corals. We also encourage contributions that integrate proxy data and models to understand the dynamics of past ocean circulation.

Keynote speaker: Jess Adkins (California Institute of Technology, USA)
Invited speaker: Ruza Ivanovic (University of Leeds, UK)

02d: What are the unifying principles common to all three Oxygen Minimum Zones (OMZs)?
Session Convenors: Jim Moffett (Univ. Southern Carolina, USA), Aurélien Paulmier (LEGOS, France)

Abstract: Oxygen minimum zones (OMZs) arise from a combination of high productivity on overlying waters and sluggish rates of ventilation within their core, giving rise to strong oxygen deficits.  In three OMZs (the Arabian Sea, Eastern Tropical South Pacific, and Eastern Tropical North Pacific) oxygen is probably effectively zero, based on recent sensor data.   These are important areas for fixed nitrogen loss on a global scale. Other OMZs, including the Benguela Upwelling and Bay of Bengal, are poised to become denitrifying on a large scale but are not so at present. These regions have complex geochemistry and a global significance that extends beyond the nitrogen cycle alone. They are critical domains in which to investigate global change, with shifts in redox chemistry and their boundaries evident or predicted to occur in the near future. Moreover, carbon preservation in underlying sediments makes them excellent regimes to study past changes in ocean processes. The purpose of this session is to explore the biogeochemical features common to all OMZs as well as the features that make them different.
Many nations have mounted expeditions to study OMZs in recent years, including several European nations, Japan, the USA and states bordering OMZs, particularly Peru, Chile and India. Three cruises in the International GEOTRACES program have been staged in denitrifying OMZ regions since 2009, by Japan, the USA and India. Researchers from these and other programs, as well as benthic studies are encouraged to participate in this session.

Keynote speaker: Bess Ward (Princeton University, USA)
Invited speakers:  Niels Peter Revbesch (University of Aahrus, Denmark), Marcel Kuypers (MPI for Marine Microbiology, Germany), Phyllis Lam (NOCS, UK), Sunil Singh (Physical Research Laboratory, India)

02e: Air-Sea Exchange, the Biological Pump, and Ocean Acidification
Session Convenors: Steve Emerson (University of Washington, USA), Doug Wallace (Dalhousie University, Canada)

Abstract: The pCO2 content of the atmosphere is regulated by exchange with the upper ocean via the solubility and biological pumps.  About one quarter of the anthropogenic CO2 introduced to the atmosphere is ultimately stored in the ocean causing a decrease in pH.  Understanding the physical, biological and chemical processes controlling the atmosphere-ocean carbon cycle are key to accurate predictions of ocean feedbacks to global warming. While there have been great advances on the relationship between air-sea exchange and wind speed, mechanisms controlling the fluxes are still uncertain.  Satellite-based estimates of the biological pump predict geographic variations that are not observed in upper-ocean, mass-balance studies.  The response of ocean pH to the anthropogenic CO2 invasion is nearly certain, but generalizations about the effects on marine biology are still tenuous.  This session explores recent advances in marine carbon cycle studies in the upper ocean and atmosphere.

Invited speakers: Henry Bittig (Helmholtz Ctr for Ocean Research, Kiel, Germany) and Jan Kaiser (University of East Anglia, U.K.)

02f: Biogeochemistry of Arctic and Antarctic sea ice systems
Session Convenors: Jun Nishioka (Univ. Hokkaido, Japan), Delphine Lannuzel (University of Tasmania, Australia)

Abstract: Observations have demonstrated that sea ice is biologically and chemically active in the global biogeochemical cycles. However, Earth system models currently represent sea ice as biologically and chemically inert. The aim of this session is to bring together those working on all aspects of sea ice biogeochemistry to gain a better understanding of the exchanges at the interface between sea ice and the atmosphere and sea ice and the ocean. We particularly encourage presentations on processes involved in the distribution of macro-nutrients, trace metals and organic carbon, as well as the uptake and production of climatically-important gases such as CO2, CH4, and DMS.

Keynote speaker: Martin Vancoppenolle (LOCEAN CNRS, Paris, France)

02g: Advances in marine N, P and Si biogeochemistry
Session Convenors: Damien Cardinal (University Pierre and Marie Curie, LOCEAN, Paris), Albert Colman (University of Chicago, USA), Masha Prokopenko (University of Southern California, USA), Christian März (Newcastle University, UK)

Abstract: Nitrogen, phosphorus and silicon are critical nutrients that help govern net primary production in the oceans and the efficiency of carbon export from the euphotic zone. Though their cycles are coupled, each element has a very distinct cycle with regard to ocean sources and sinks, modes of internal recycling and residence times. The biological requirements, remineralization pathways, and chemical characteristics (redox state, solubility, coupling with carbon) diverge in many important ways, leading to formation of biogeochemically diverse oceanic regions. In the recent years numerous methodological advances have been developed and several basic concepts revisited with regard to these key macronutrients (e.g. diazotrophy, Redfield Ratios…). This session will focus on the new insights gained by application of such analytical and modeling approaches. We will particularly encourage contributions dealing with inter-elemental (de)coupling, multi-spatial scales (from cell to global), and/or multi-temporal scales (from geologic past to future).

Keynote speaker: Laetitia Pichevin (University of Edinburgh, UK)
Invited speakers: Greg de Souza (Princeton University, USA), Kate Hendry (Bristol University, UK), Caroline Slomp (University of Utrecht, The Netherlands), Claire Mahaffey (University of Liverpool, UK), Curtis Deutsch/Tom Weber (University of Washington)

02s: Goldschmidt 25th Anniversary

Catherine Jeandel, GEOTRACES IPO senior scientist, reviewed the last 25 years of marine geochemistry.
Her talk is available to download here.