92 WORKSHOP REPORT

doi.org/10.22498/pages.26.2.92 The role of dust in climate change: A biogeochemistry perspective Gisela Winckler1, F. Lambert2 and E. Shoenfelt1 Las Cruces, Chile, 8-10 January 2018

Mineral-dust aerosols are critically important components of climate and Earth system dynamics as they affect radiative forcing, precipitation, atmospheric chemistry, sur- face albedo of ice sheets, and marine and terrestrial biogeochemistry, over significant portions of the planet. Dust-borne iron is recognized to be an important micronutrient in regulating the magnitude and dynamics of ocean primary productivity and affecting the carbon cycle under past and modern climate conditions. Paleodata suggest large fluctua- tions in atmospheric dust over the geologi- cal past. However, dust-transport models struggle to reproduce observed spatial and temporal dust-flux variability. In addition, ob- servational and modeling studies based in the current climate suggest that not all iron Figure 1: Representation of the major processes in the ocean iron cycle from Tagliabue et al. 2017. Reprinted by in dust is equally available to continental and permission from Springer Nature. ocean biota. Iron solubility varies dramati- cally, depending on mineralogy and state of emissions, from geochemically identifying that may have been more highly impacted by soils, as well as atmospheric processing by and tracing source regions to deposition in glacier physical weathering, and have been acids. Modeling studies, however, still mostly the surface ocean. Participants discussed the shown to have a different mineral composi- assume constant solubility. effects on the solubility and bioavailability tion as a result. The goal of this effort is to of iron at each of these stations in the dust combine the highly varied range of expertise The PAGES Dust Impact on Climate and cycle, including the influence of dust source to better quantify the bioavailable iron in dif- Environment (DICE) working group held its and mineralogy on dust solubility and bio- ferent dust sources across space and time. first workshop on The Role of Dust in Climate availability, the role of atmospheric process- Change: A Biogeochemistry Perspective. ing in dust solubility, and the importance AFFILIATIONS Twenty-seven experts from nine different of organic ligands and aggregation to iron 1Lamont-Doherty Earth Observatory, Columbia countries came together at the Coastal lifetime in the mixed layer of the ocean for University, New York, USA Marine Research Station of the Catholic bioavailability in modern and past oceans. 2Department of Physical Geography, Pontifical University of Chile in Las Cruces for the Catholic University of Chile, Santiago, Chile three-day workshop that was jointly sup- Halfway through the workshop, partici- CONTACT ported by PAGES and the Chilean Comisión pants split into three breakout groups for Gisela Winckler: [email protected] Nacional de Investigación Científica y extended discussion on the following three Tecnológica. About half of the participants avenues of future research (1) Ocean iron REFERENCES were early-career researchers or scientists sources (aeolian versus others), (2) Iron Tagliabue A et al. (2017) Nature 543: 51-59 from developing countries. The workshop solubility past, present, future, and (3) Dust format combined keynote talks with shorter particles: shape, size and composition. thematically matching pop-up talks, followed by discussion and brainstorming of future As a direct interdisciplinary outcome of the research avenues among all participants. workshop, participants are developing a model that evaluates the relative importance This workshop was a highly interdisciplin- of atmospheric processing, mineralogy, size ary effort to better quantify and simulate fraction, settling rate, and ligand-mediated biogeochemical impacts of dust deposition. dissolution on the solubility of dust-borne It gave observationalists and modelers the iron that reaches the ocean (Fig. 1). This is chance to combine perspectives on the role in an effort to combine experimental and of dust in ocean biogeochemical cycles and modeling results to improve the estimates the greater carbon cycle. The specific goal of of iron solubility in biogeochemical models – the workshop was to more precisely quantify moving beyond the assumptions of constant the effects of mineral dust, and specifically iron solubility. The group plans to combine iron, during various climate states, and to observational data on dust-source mineral- strategize how to further foster this relation- ogy, dust deposition, atmospheric process- ship in future work. ing, and ligand concentrations and strengths with kinetic models of dust dissolution in the The major themes of the keynote pre- water column. Such a model can be applied sentations followed the pathways of dust to both modern as well as past dust sources

PAGES MAGAZINE ∙ VOLUME 26 ∙ NO 2 ∙ November 2018 CC-BY