PAGES Magazine articles
David W. Lea1, M. Kienast2, T. de Garidel-Thoron3, M. Kageyama4, A. Paul5 and E. Bard3
Corvallis, USA, 3 December 2013
Establishing a sea surface temperature (SST) distribution for the Last Glacial Maximum (LGM) has long been a primary goal in paleoclimate research, with the CLIMAP (Climate Long range Investigation, Mapping and Prediction) reconstruction standing out as a landmark accomplishment. The development of new SST proxies such as UK37’ and Mg/Ca paleothermometry in the 1980s and 90s spurred the international community to re-evaluate LGM SSTs. The publication of the SST reconstruction of MARGO (Multiproxy Approach for the Reconstruction of the Glacial Ocean surface) was the culmination of an international collaboration to update and improve LGM SST reconstructions (MARGO Project Members 2009). The MARGO reconstruction is an important validation target for the modeling community because the climate forcing and response during the LGM are relatively well known and allow for an assessment of climate sensitivity determinations.
The purpose of the COMPARE 2013 workshop was to follow up on an initial meeting of COMPARE 2012 (Comparing Ocean Models with Paleo-Archives) in Bremen, Germany (18-21 March 2012) which had discussed ways to further improve the MARGO data set and how to apply it to data-model intercomparisons (Kucera et al. 2012). The MARGO SST reconstruction synthesizes both more traditional approaches (i.e. faunal transfer functions) and newer geochemical approaches (i.e. Mg/Ca and UK37’). But because the original MARGO data set for the tropics is still dominated by estimates based on transfer functions, the reconstructed SST changes do not optimally represent the different proxy results. The COMPARE 2013 workshop brought together observationalists and modelers to exchange their latest insights on tropical SST proxies and the efficacy of the MARGO low latitude reconstructions.
There are many reasons for re-evaluating LGM tropical SST, including the MARGO compilation itself, which displays a much stronger level of spatial heterogeneity in the tropics than has been simulated by coupled model runs (Kageyama et al. 2013); the validity of the SST proxies and their overall compatibility; advances in linking climate sensitivity to LGM tropical cooling in models (Hargreaves et al. 2012); downward revisions of LGM cooling based on MARGO; and advances in analyzing and attributing deglacial SST records, which are increasingly based on geochemical proxy records (Shakun et al. 2012).
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Figure 1 (A): Distribution of newly available low latitude records (black dots) compared to the MARGO (2009) dataset (red dots) that have Mg/Ca (top panel) and UK37’ (lower panel) paleothermometry data. Note that sites are concentrated along oceanic margins. (B) Whisker plot comparison of low latitude UK37’ and Mg/Ca data compiled in MARGO (2009). On average, Mg/Ca data indicates 3°C of tropical cooling vs. 2°C for UK37’. |
We identified two overarching research questions to frame the problem:
• Can we reconcile UK37’ and Mg/Ca data within acceptable brackets by using harmonized calibration schemes and by considering differences in habitat depth and season? If so, what was the magnitude of mean annual LGM tropical surface cooling?
• How much heterogeneity was there in tropical surface cooling during the LGM?
To address these questions, we propose to develop a new LGM tropical SST geochemical database. This database will focus on measured parameters: i.e. raw Mg/Ca and UK37’ measurements (Fig. 1). It will include the full data sequence from 0-30 ka BP with chronological constraints and uncertainties, associated parameters such as oxygen isotopes, alkenone abundance, dissolution parameters, Mg/Ca on other species, and relevant metadata (e.g. how the samples were processed or cleaned, foraminiferal size fraction and morphotypes).
The proposed approach will provide an SST field using harmonized calibrations, which will allow direct comparison of Mg/Ca and alkenone temperatures. It will also provide a basis of comparison with the MARGO (2009) database as well as a target for modeling. Statistical analysis of the dataset, considering the interproxy difference, the spatial reproducibility, as well as the calibration uncertainty, will provide uncertainty estimates for the SST field. The raw measurements can also be adapted to improved or alternative calibrations, data assimilation or forward modeling. Furthermore, assembling a database with records covering the full sequence since the last glacial opens the possibility of developing time slices for target periods other than the LGM (e.g. Heinrich Stadial 1 or the Younger Dryas).
We will try to implement a dynamic database approach that allows for the addition of new data as they become available, and, possibly, implementation of different calibration schemes. We invite members of the paleoceanographic community to submit UK37’ and Mg/Ca data sets that will enhance the COMPARE effort.
affiliations
1Department of Earth Science, University of California, Santa Barbara, USA
2Department of Oceanography, Dalhousie University, Halifax, Canada
3CEREGE, Aix-Marseille Université, Aix-en-Provence, France
4LSCE/IPSL, Gif-sur-Yvette, France
5MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany
contact
David Lea: lea
geol.ucsb.edu
references
Hargreaves JC et al (2012) Geophys Res Lett 39, doi: 10.1029/2012GL053872
Kageyama M et al. (2012) Clim Dyn 40: 2469-2495
Kucera M et al. (2012) PAGES news 20(2): 102
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Johann H. Jungclaus1, H. Goosse2, E. García-Bustamante3,4, L. Fernández-Donado4 and J.F. González-Rouco4
Madrid, Spain, 4-6 November 2013
Comparing model simulations with proxy-based climate reconstructions offers the possibility of improving our understanding of the mechanisms contributing to climate variability and their links to external forcing or internal processes. It helps to identify deficiencies in the way climate variability is represented by proxy records or by model simulations, with implications for future climate change projections. The Past2K group of the Paleoclimate Modelling Intercomparison Project (PMIP3) is promoting model-data comparison activities focusing on the climate of the last millennium. The PAGES 2k Network is fostering similar activities covering the last 2000 years and has promoted the development of regional-scale data syntheses resulting in an ensemble of reconstructions for nearly all the continents (PAGES2k Consortium 2013). The meeting held in Madrid gathered members of both communities with a main focus on comparing the PMIP3 “past1000” simulations with the PAGES2k reconstructions.
Activities started a few months before the actual workshop as most of the 32 workshop participants volunteered to contribute to the analyses of some diagnostics within one of the three working groups (WGs) focused on: 1) PAGES2K regions and PMIP3 simulations; 2) PMIP3 simulations and reconstructed circulation modes; 3) best practices and new approaches in model-data comparison. In addition, participants were identified to prepare reviews. The three-day meeting was structured into review talks (days 1 and 2) and WG presentations (days 2 and 3), allowing time for ample discussion slots. The last day of the workshop focused on discussion and planning future joint activities, including 1) the preparation of manuscripts focused on the comparison of PMIP3 simulations and PAGES2k regional reconstructions, 2) comparison between reconstructed and simulated modes of variability, and 3) on best practices in data-model comparison. Additionally, an outreach event was organized on communicating climate and climate change science.
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Figure 1: Correlation values between PAGES2k reconstructions and PMIP3 (grey) and pre-PMIP3 (black) simulations. Regions are depicted with colors. The full (empty) circles indicate a correlation value (not) significantly different from zero (p<0.05). The gray shaded area highlights the simulations that included a comparatively lower solar forcing variability scenario. Time series were 31-year low pass filtered and the full period of overlap between simulations and reconstructions used. See Table 5.A.1 in Masson-Delmotte et al. (2014) for details on model names and forcing. |
Several issues from the discussions can be highlighted. For instance, significant correlations between regional temperature reconstructions and climate model simulations (Fig. 1) suggest that, at multidecadal scales and above, regional temperatures respond to external forcing (PAGES2k Consortium 2013; Sundberg et al. 2012; Schurer et al. 2014). The specific fingerprints of volcanic, solar and anthropogenic contributions were analyzed from the perspective of various methodologies, with the role of solar forcing being acknowledged as comparatively smaller. The inter-regional correlations were shown to be lower in the reconstructions than within the models’ world, the latter evidencing a more homogeneous spatial temperature response. The implications of these differences for climate reconstructions and also for the assessment of confidence in climate models were discussed.
The reconstructions of modes of atmosphere and ocean variability such as PDO, ENSO, IPO, PNA, NAO, SAM or the gyre system in the North Atlantic were presented. In most cases, they show very limited resemblance to their simulated counterparts. This suggests an overall lack of evidence for a direct external forcing imprint on the variability of many climate modes. Since internal variability seems to be the dominant factor, model simulations are useful for identifying the dynamics explaining some of the reconstructed changes. However, a more fundamental issue with methodological implications is the limited agreement found in various reconstructions of particular modes. Such inconsistencies may reflect large spatial changes in the positions of the centers of action that are not captured with index definitions based on fixed locations or eigenvector approaches. Here, model-guided mode definition and proxy-site selection (e.g. Lehner et al. 2012) appears to emerge as a promising field of research.
acknowledgements
The organizers thank PAGES, MINECO-FECYT (FCT-13-6276), IGEO and the Asociación Española de Climatología for the funding and/or support that made this workshop possible; E. Lucio for producing the workshop logo; Círculo de Bellas Artes de Madrid and Plataforma Audiovisual UCM for their assistance with the outreach event.
Meeting website: www.palma-ucm.es/members/workshop/Home.html
Outreach event: www.palma-ucm.es/activities/
affiliations
1Max Planck Institute for Meteorology, Hamburg, Germany
2Georges Lemaître Centre for Earth and Climate Research, Université catholique de Louvain, Belgium
3Department of Physics, University of Murcia, Spain
4Institute of Geosciences, CSIC-UCM, Complutense University of Madrid, Spain
contact
Johan H. Jungclaus: johann.jungclausmpimet.mpg.de
references
Lehner F et al. (2012) Quat Sci Rev 45: 85-94
PAGES 2k Consortium (2013) Nat Geosci 6: 339-346
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Andreas Schmittner1, S.P. Harrison2, A.E. Carlson1, A.C. Mix1, M. Kageyama3 and M. Kucera4
Corvallis, USA, 4-6 December 2013
More than 40 scientists met in Corvallis, Oregon, to discuss how ocean data can be better used to evaluate results from the Paleoclimate Model Intercomparison Project (PMIP). Focus was on the Last Glacial Maximum (LGM; 19-23 ka ago) and the Mid-Holocene (MH; 6 ka ago). However, many talks went beyond these time periods and showed new and exciting paleodata from the deglacial transition from the LGM to the Holocene, and model simulations. The idea of a new community experiment for transient modeling of the deglaciation in the next PMIP was discussed with enthusiasm.
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Figure 1: Comparison of deep (2 km) ocean δ13CDIC distributions in modern observations (top left) and three different circulation models calculated using the same underlying biogeochemistry model (MOBI; Schmittner et al. 2013) and transport tracer matrix method (Khatiwala et al. 2005). The model simulations do not account for the anthropogenic rise in atmospheric δ13C. Note the effect of higher resolution (1°×1° MIT-ECCO lower right) on the simulation of the western boundary current in the Atlantic compared with the coarser resolution models (2.8°×2.8° MIT upper right and 1.8°×3.6° UVic lower left). PMIP3 LGM simulations using this offline method of calculating tracer distributions will be used in the future to predict isotope distributions for comparison with paleo data from ocean sediments. |
Talks and discussions during the first day focused on methods of model-data comparison (Fig. 1), quantifying uncertainty and ocean temperature reconstructions, particularly from the tropics (including a report from a one-day preluding workshop on tropical sea-surface temperatures). Systematic differences between various proxies (e.g. alkenones, Mg/Ca, TEX86, foraminifera faunal assemblages) were diagnosed and new methods of quantifying uncertainties and forward modeling of individual foraminifera species were presented. It appears likely that the seasonal and vertical attribution of sea surface temperature reconstructions is a major reason for discrepancy among different proxies. Contrary to previous interpretation, it seems that in some cases foraminifera assemblages do record shallow subsurface temperatures rather than surface temperatures. Temperatures at the subsurface may also show larger climate signals than at the surface in some areas, as suggested by model simulations.
The second day focused on the deep ocean. Stable carbon isotopes (δ13C) and radiocarbon (Δ14C) provide important constraints on deep-ocean circulation and carbon cycling. Inverse model solutions using δ13C data indicate that the Atlantic Meridional Overturning Circulation (AMOC) during the LGM may not have been significantly different from today. Another presentation highlighted that in model simulations of the LGM, ocean circulation requires thousands of years to equilibrate. This raised the issue of whether the LGM (or in fact any time interval) can be considered to ever be in an equilibrium state, either for models or data reconstructions. Although radiocarbon is perhaps the most direct proxy for deep ocean circulation, independent dating is needed to allow its interpretation as a circulation tracer. The assumption of constant surface reservoir ages made in many previous studies may in some cases not be true, at least during the deglaciation. Nevertheless, new radiocarbon data from the North Pacific and Southern Ocean advance our understanding of deep ocean circulation changes during the LGM and deglacial intervals.
Modeling studies highlighted the role of Laurentide ice-sheet topography in affecting global-mean LGM climate, model biases in the Southern Ocean for AMOC LGM simulations, and uncertainties in physical and biological processes in reproducing carbon cycling in the ocean.
During the last day, the potential for focused studies of past warm periods and new approaches to community databases were discussed. One presentation argued that an unfavorable signal-to-uncertainty ratio in the currently available sea surface temperature reconstructions prevents the use of MH data in constraining model simulations. Model simulations of the Miocene considering changes in the Antarctic ice sheet were also presented.
Databases are essential for the efficient creation of syntheses and for making paleoceanographic data more accessible. Two new approaches were introduced: one web based system and one offline tool, both of which can be expected to become available to the community in 2014.
The workshop proceeded with discussions in breakout groups on data reporting standards, model-data comparison, and an outline for new PMIP simulations of the deglacial. A document recommending paleoceanographic data reporting standards has been started and will be further developed through PAGES. Another document outlining the discussions of the proposed new deglacial PMIP simulation was started and will be presented to the wider PMIP community at the upcoming PMIP3 conference in May 2014. This workshop was co-sponsored by the US NSF, PAGES, and INQUA. The meeting program and all of the abstracts can be found at:
http://people.oregonstate.edu/~schmita2/Projects/PMIP_LGM_C13/PMIP_ocean_WS.html
affiliations
1College of Earth, Ocean, and Atmsopheric Sciences, Oregon State University, Corvallis, USA
2Centre for Past Climate Change, University of Reading, UK and Department of Biological Sciences, Macquarie University, Sydney, Australia
3Laboratoire des Sciences du Climat et de l’Environnement/IPSL, Gif-sur-Yvette, France
4Center for Marine Environmental Sciences, University of Bremen, Germany
contact
Andreas Schmittner: aschmittcoas.oregonstate.edu
references
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Sonia L. Fontana1 and Keith D. Bennett2
Jujuy, Argentina, 19-30 August 2013
Paleoecological studies provide data on changes in vegetation and other aspects of the environment through time. Numerous paleoecological records from around the world have demonstrated that vegetation has changed, often dramatically, since the last glacial maximum (LGM). Changes are usually attributed to various external forcing factors, including climatic change, volcanic eruptions, fire, or human activity. Additionally, vegetation has changed as result of its own internal dynamics (Bennett and Willis 1995), which include migration, competition and succession across different timescales. An example of postglacial changes in vegetation from southern-most South America is illustrated in Figure 1; it specifies the different processes that have caused vegetation changes since the LGM (Fontana and Bennett 2012). Disentangling these forcing factors of environmental change is challenging, especially when they operate and interact at different spatial and temporal scales (Fontana et al. 2012).
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Figure 1: Pollen percentage diagram of selected taxa from Lake Ballena, indicating different processes that have caused main vegetation changes since the LGM. MB2 indicates the position of the tephra layer from the Mt Burney 2 eruption. Figure modified from Fontana and Bennett (2012). |
The purpose of this workshop was to bring together Latin American researchers working on Quaternary environmental change to discuss and build up a network, exchange perspectives and promote international interactions. Forty-two senior and early career scientists, and postgraduate students from Mexico, Venezuela, Colombia, Brazil, Bolivia, Chile and Argentina attended the meeting. A broad range of expertise was represented covering palynology, diatoms, ostracods, foraminifera, nanoplankton, charophytes, phytoliths, dendrochronology, and archeology.
The workshop provided (1) an overview of the spatial and evolutionary responses of organisms to different Quaternary driving forces with the aim of providing insight into general questions of species survival, spread and biodiversity; (2) an outline of the principles, methods and applications of selected paleoecological techniques; and (3) an overview of methods and software used for data analyses.
The event comprised lectures, practical classes, poster presentations, a field trip and the development of a joint research project. The lectures addressed the paleoecology of the oceans, long Quaternary terrestrial records with multiple glacial-interglacial oscillations, an overview of key sites for the last glacial-interglacial transition, paleogenetics (including molecular clocks and ancient DNA), refugia, individualistic communities, plant migration, late Quaternary extinctions, and consideration of the role of Quaternary events on the evolution of organisms. Important discussions centered around data collection issues: site selection and coring, sub-sampling techniques, routine sediment analyses, overview of pollen and macrofossil analyses and the value of multi-disciplinary research in paleoenvironmental reconstructions. The practical classes focused on data handling: chronology, the radiocarbon method and calibration, zonation, rate of change, ordination techniques and diversity estimates.
A field trip to Laguna Rontuyoc took place, following which participants engaged in the Latin American co-operative project for young scientists, Synergy Latina, and designed a multi-disciplinary research project with the main goal being to disentangle possible interactions between the environment and humans of the Altiplano of northern Argentina. Attention was paid to the influence that climatic changes had on the development of Andean civilizations and the consequent impact of human activities on the landscape. The initial phase of this project was conducted during the course (describing and sub-sampling the sediment core), while the different analyses will be carried out at a later stage at the participants’ home institutions.
This first workshop was hosted by the University of Jujuy and coordinated by Julio Kulemeyer and Liliana Lupo. It was a successful start to the task of enhancing paleoecological investigations in Latin America and we look forward to larger scale joint investigations, the ongoing exchange of knowledge leading to the development of new ideas and research questions, and continued cooperation. Further annual workshops are planned.
In addition to PAGES, participants received support from their home institutions, universities and research councils. The 14CHRONO Centre at Queen’s University Belfast, financially supported and ran the radiocarbon dating of the sediment records for the Synergy Latina project.
The full program of activities, including poster abstracts can be viewed at: www.uni-goettingen.de/en/413062.html.
affiliations
1Department of Palynology and Climate Dynamics, University of Göttingen, Germany
2School of Geography, Archaeology & Palaeoecology, Queen's University Belfast, Northern Ireland, UK
contact
Sonia L. Fontana: Sonia.Fontanabiologie.uni-goettingen.de
references
Bennett KD, Willis KJ (1995) Gior Bot Ital 129: 243–254
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Eva Calvo1, I. Cacho2, C. Pelejero1,3, J.O. Grimalt4, P.G. Mortyn5, R. Zahn3,5
and P. Ziveri5
11th International Conference on Paleoceanography – Sitges, Spain, 1-6 September 2013
Over the past 30 years, the International Conference on Paleoceanography (ICP) events have established a strong tradition in pushing paleoceanographic research forward, as well as witnessing and stimulating the great progress and achievements that this multi-disciplinary field has made. The ICP11 took place in Sitges, a small Mediterranean coastal hamlet south of Barcelona, and was attended by 576 participants (including 196 students) from 41 different nationalities.
The conference was organized along five themes, addressed through five plenary sessions. The mornings were dedicated to oral presentations (30 in all) and three poster sessions were held in the afternoons, featuring a total of 527 posters. The Scientific Committee designed the session themes to guarantee a multidisciplinary approach to past climates at various timescales, from the most recent past back to the Paleozoic using both empirical and modeling approaches (the full program is available at: www.icp2013.cat). ICP11 also committed to providing early-career scientists the opportunity to present their research to an international audience, and therefore they accounted for more than half of the selected speakers. For the first time in ICP events, three “perspective lectures” were included: two highlighting work in disciplines closely related to paleoceanography - modern ocean geochemistry from the GEOTRACES program’s perspective, and ice core paleoclimate studies and the third presenting the ideas for a follow-up project to the International Marine Global Change Study. As in previous ICPs, the Scientific Committee awarded 12 students poster prizes (www.icp2013.cat/index.php/best-student-awards.html).
A number of challenging and important findings were presented during the ICP. For example, we learned of advances and refinements in geochemical proxies and their application on issues such as sea ice cover (IP25), ice sheet stability (Nd isotopes, Sr-Nd-Pb isotopes) or glacial CO2 sequestration (radiocarbon, B isotopes, foraminifera-bound N isotopes, C isotopes).
Participants also learnt of remarkable efforts to combine major “data mining” and modeling to examine global and regional oceanographic patterns and causes of past climate changes. These efforts focused on several climatic and oceanic variables including global and regional temperature changes since the Last Glacial Maximum, the Meridional Overturning Circulation over the last 40 ka, ocean oxygenation across the last deglaciation and a sea surface temperature compilation for the past two millennia, conducted by the PAGES Ocean2k project.
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Figure 1: “Castells”, Human Towers, a Catalan tradition that accelerates your heartbeat. This picture shows a performance of the “Castells of Poble Sec” during the ICP11 ice breaker with the participants’ help to support the tower. This is an excellent example of team effort and the importance of every single member to the success of the project, in this case, the human tower. “Team spirit, strength, balance, courage and common sense”, the “castells” motto also defines the essence of the ICP conferences and the paleoceanographic community. |
New geochemical records and modeling experiments provided insight on the coupling between past climates and ocean biogeochemistry, in general, and the carbon cycle in particular. Evidence of the breakdown of North Pacific stratification during the last deglaciation prompted a lively discussion on the possibility of North Pacific deep-water formation at that time. At millennial time scales, modeling simulations also showed the relevance of circulation changes, both in the Atlantic and in the Pacific, in controlling atmospheric CO2. At longer time-scales, an unusual attempt to shed light on the C isotopic vital effects in coccoliths provided a new avenue to detect a global atmospheric CO2 decrease about 7-5 Ma ago that was coupled to ocean temperature decrease. For these ancient times, a wealth of new results from deep-time paleoceanography and paleomodeling demonstrated the substantial recent progress in quantitatively tackling several key parameters, such as deep-ocean oxygenation during extreme climates and exotic events of the Cenozoic and beyond.
Efforts to improve the resolution and accuracy of marine proxy records were also presented, and the associated value for gaining further knowledge about ocean-land-atmosphere interactions was demonstrated. Excellent examples came from coral records, which allow us to more accurately decipher past inter-annual climate variability such as the El Niño-Southern Oscillation, but also from sediment and pollen records from the Mediterranean, the Atlantic and Antarctica’s margins.
Another memorable event of the conference was the traditional ICP paleomusicology concert where conference attendees put on a diverse range of outstanding musical performances for their colleagues. The next tri-annual meeting, ICP12, will be held in Utrecht in The Netherlands in summer 2016.
acknowledgements
The organizers thank PAGES and SCOR for their financial support allowing 19 students and early career scientists from developing countries to attend ICP11. We also thank EGU for supporting three key contributors as EGU Ambassadors. Nature Publishing Group provided five subscriptions for student poster presentation awards.
affiliations
1Institute of Marine Sciences, CSIC, Barcelona, Spain
2Faculty of Geology, University of Barcelona, Spain
3Catalan Institution for Research and Advanced Studies, Barcelona, Spain
4Institute of Environmental Assessment and Water Research, CSIC, Barcelona, Spain
5Institute of Environmental Science and Technology, Autonomous University of Barcelona, Spain
contact
Eva Calvo: ecalvoicm.csic.es
Zuzia Stroynowski1, R. Minzoni2 and S.K. Shukla3
Cardiff, UK, 4-9 August 2013
The Polar Marine Diatom Workshops (PMDW) arose to meet the need for a forum that would encourage the exchange of taxonomic skills and associated new techniques, while providing an excellent platform for students to receive training and guidance from experienced diatomists. Since 2005, the workshop has become a successful biennial event, bringing polar diatomists together to exchange new ideas, share recent results and data, and build future collaborations with other researchers around the world. The 4th PMDW was hosted by Jennifer Pike at Cardiff University and was attended by 36 participants from 14 countries. It consisted of research presentations and practical microscope-based sessions on polar diatom taxonomy and ecology.
Diatoms are a major phytoplankton group accounting for 40% of global marine primary productivity; in high latitudes this figure is over 60%. They play an integral role in the export of carbon and are extremely sensitive to changing environments. As research continues in the polar regions, novel applications emerge as a result of our increased understanding of species-specific ecology. Diatom studies in such extreme environments are essential for improving our understanding of glacio-marine settings - an understanding that may be applied to reconstruct paleoenvironments including temperature, sea ice extent, the growth and decay of ice sheets, and to assess future climate scenarios. The PMDW provided an indispensable forum for polar diatomists to discuss all these issues.
Fifteen 1.5-hour microscope sessions dominated the week’s activities, and were complemented by nine 30-minute lectures and 12 poster presentations. Microscope tutorials spanned both the Arctic and Antarctic, and covered topics on diatom morphology, modern day communities, fossil records and biostratigraphy.
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Figure 1: Morphometrics of horned diatom Eucampia antarctica as a proxy for sea-ice occurrence during Marine Isotope Stage 5 at Drygalski Basin, Antarctica (M.A. Bárcena, personal communication). The ratio of Terminal (T) and Intercalary (I) valves is calculated as a measure of chain length. Longer chains (i.e. lower T:I) indicate higher light conditions and thinner/less sea-ice cover (Fryxell and Prasad 1990). The interpretation of these results differs from a Fragilariopsis Index that compares sea-ice related species F. curta with open marine species F. kerguelensis (after Denis et al. 2010), and suggests our understanding of these proxy indices needs to be updated. |
Some of the highlights of the meeting were the following: M. A. Bárcena presented new data on Eucampia antarctica as a proxy for paleoceanography and sea-ice concentration in the Drygalski Basin (Fig. 1). Under higher light intensity and thinner/less sea-ice cover, E. antarctica undergoes more cell divisions and average chain length increases (Fryxell and Prasad 1990). However plankton net samples (L. Armand) suggest this paleoproxy may underestimate sea ice extent because the ratio used to estimate chain lengths from fossil frustules might be biased.
R. Crawford presented a new morphological investigation on the understudied genus Corethron. This was further complemented by modern-day plankton net studies at Anvers Island and Biscoe Bay, Antarctica, where Corethron sp. dominated the assemblage (D. Karentz). Future work will compare species with environmental variables as well as RNA sequencing to determine their proteinic response to temperature changes (D. Karentz). A. Leventer presented a laminated Corethron ooze record from Iceberg Alley, East Antarctica.
C. Allen ran a practical session on the largely overlooked giant diatom species Arachnoidiscus sp. from the Firth of Tay, Antarctic Peninsula. The importance of this species to the silica and carbon export budget was discussed. Another large species, Coscinodiscus sp. and its morphology and identification were presented in practical sessions with sedimentary samples from Southern Iceland (K. Hendry) and plankton net samples from Admiralty Bay, Antarctica (B. Jerzak).
R. Jordan and K. Abe presented Eocene diatoms from IODP 302 (Arctic) and other siliceous fossils. The earliest diatom Cretaceous deposits were also reviewed and their origins discussed (D. Harwood).
One of the goals of the workshop was to provide a launch pad for future collaboration between early career and established researchers, and we hope to see the fruits of these collaborations at the 5th PMDW, which will be take place at Salamanca University, Spain in 2015. Further information about the workshops, previous workshop publications and future events can be found at: https://sites.google.com/site/polarmarinediatomworkshop/. This workshop was supported by PAGES, the Micropalaeontological Society, Linnean Society of London, BetaAnalytic, GX Optical, and the Annals of Botany Company.
affiliations
1Marine Geology Division, Portuguese Institute of Ocean and Atmosphere, Portugal
2Department of Earth Science, Rice University, Houston, USA
3Department of Marine Sciences, Goa University, India
contact
Zuzia Stroynowski: zuzia.stroynowskiipma.pt
references
Fortunat Joos1, B. Otto-Bliesner2 and E. Brady2
Bern, Switzerland, 26-28 August 2013
Isotopes of water, carbon, oxygen, and of rare earth elements offer the opportunity to quantitatively understand physical and biogeochemical processes in the Earth System and to unravel past and modern climate change. Past climate and greenhouse gas variations provide insight into how climate might evolve under ongoing anthropogenic forcing. Yet, our understanding of past climate and biogeochemical variations over glacial-interglacial time scales, of past abrupt climate swings, or of climate variability during the last few millennia is still limited. The mechanisms of past climate change are intensively debated. What drives glacial inceptions and terminations? How and why did precipitation vary in the monsoon system and at high latitudes? How did ocean circulation evolve? What regulated the reconstructed variations in atmospheric CO2 and other greenhouse gases?
The obstacles to exploiting the full potential of isotopes in order to answer these questions include the scarcity of measurements and of easily accessible and quality-flagged isotope data compilations from paleoclimate archives, incomplete understanding and corresponding uncertainties in isotope process parameterizations in Earth System models, and a lack of systematic multi-model model-data intercomparisons for isotopes.
More than 80 participants attended this conference organized by the Oeschger Centre for Climate Change Research and the Climate and Environmental Physics group at the University of Bern in collaboration with the CESM Paleoclimate Working Group at the National Center for Atmospheric Research. The meeting is intended to be the fist in a series of conferences. The objective is to provide a networking platform for specialists from the data and modeling communities to integrate information from isotopes across the Earth System components and scientific disciplines, to assess the state-of-the art, and to identify and address knowledge gaps.
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Figure 1: Spatio-temporal evolution of δ13C in the deep ocean (> 3000 m) as reconstructed from ocean sediment data (symbols) and simulated with an Earth System Model of Intermediate Complexity. The map shows the total change over the Holocene; the right panel shows the evolution from the stacked proxy data (grey) and the globally-averaged model results (blue). |
The presentations as well as the many outstanding posters addressed a broad set of topics including using water isotopes in speleothems to reconstruct temperature and precipitation changes; using carbon and water isotopes in ice cores and marine sediments to understand past climatic and biogeochemical changes (e.g. Fig. 1); the constraints on past ocean circulation from rare earth and carbon isotopes; N2O and nitrogen isotopes in ice cores; how carbon and water isotopes in tree rings can be used to identify physiological mechanisms and document environmental change; the representation of isotopes in models; the interpretation of reconstructed changes with the help of models; the exploitation of synergies between process models, contemporary observations, Earth System Models and paleodata; and the use of present-day monitoring and dedicated process studies for the interpretation of proxy data.
As highlighted in the presentations, much progress has been made in recent years to reconstruct isotopic composition in various archives. Improved proxy records are emerging that extend the previous scope in spatial and temporal resolution and will permit us to draw a more and more detailed picture on their spatio-temporal evolution. At the same time, isotopes of carbon and water and of rare earth elements are increasingly implemented as a standard module in comprehensive Earth System Models and in Earth System Models of Intermediate Complexity.
Concluding discussions revolved around the best way to organize and quality flag existing isotope data to make them more easily accessible to the modeling and experimental communities. It is expected that the meeting stimulated bottom-up research initiatives among the participants that will foster progress on the use of various geotracers in paleoclimate research, in particular in the form of new collaborative efforts that combine information from models and proxies. A follow-up conference is planned to be held in Paris, following the template of this first event in Bern.
acknowledgements
The organizers thank the Oeschger Centre for Climate Change Research, PAGES, and the Johanna Dürmüller-Bol Foundation for the generous financial support that made this workshop possible. More information, including the abstracts and program, is available at www.oeschger.unibe.ch/events/conferences/isotopes/
affiliations
1Oeschger Centre for Climate Change Research and Physics Institute, University of Bern, Switzerland
2National Center for Atmospheric Research (NCAR), Boulder, USA
contact
Fortunat Joos: joosclimate.unibe.ch
Eric W. Wolff1, R. Gersonde2 and A. de Vernal3
2nd Sea Ice Proxies (SIP) Working Group workshop - Cambridge, UK, 22-24 July 2013
The recent rapid reduction in the extent and volume of Arctic sea ice makes it especially urgent to obtain long time series that can allow us to put recent events in context. The satellite dataset reaches only 40 years into the past, while syntheses using ship and aircraft observations have been taken back to the late 19th century. Before that, we are reliant almost entirely on proxy data – from marine sediments, ice cores, and coastal material, each providing evidence of past sea ice presence or absence.
However, there is generally a complex chain of processes connecting ice extent or presence to the measured proxy. An assessment of the basis for each individual proxy was the main business of the first SIP workshop in Montréal in 2012 (de Vernal et al. 2013a). This resulted in a special issue, entitled “Sea Ice in the Paleoclimate System: the Challenge of Reconstructing Sea Ice from Proxies” in the journal, Quaternary Science Reviews. Among the 18 papers published, there are three authoritative review papers, one on the use of dinocysts to estimate northern hemisphere sea ice (de Vernal et al. 2013b), another on the biomarker IP25 (Belt and Müller 2013), and the last on ice core proxies of sea ice extent (Abram et al. 2013). An introductory paper (de Vernal et al. 2013c) provides a table highlighting the advantages and disadvantages of each method.
The second workshop took this as its starting point and proceeded to explore the new ideas that had emerged in the last year. Although most of the work discussed was based on proxies discussed at the first workshop, a new candidate proxy in ice cores (halogens) was presented, and the use of material such as driftwood and sedimentological material was also considered.
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Figure 1: Through its three workshops, SIP has considered all the issues (of sampling, measurement, process understanding, reporting and statistics) which intervene between measurements of different proxies and the production of sea ice reconstructions that are suitable for comparison with modern data and models. |
The main issue for the workshop was to consider ways in which multiple proxies from many sites can be used together to create credible reconstructions of sea ice proxies. Issues arise at each stage (Fig. 1). For some proxies, such as the biomarker IP25, even ensuring comparable analytical results is challenging. A recent intercomparison exercise was presented, and based on this, new recommendations for standardizing analytical methods will be prepared. Once the measurement is complete, it is often reported in terms of a sea ice property, such as seasonal extent, presence/absence, or months of ice cover. The basis for calibrating each proxy against a particular property needs careful examination. Study of the modern processes that link ice to, for example, a biological vector that may be present only seasonally, and to its deposition in sediment, is essential. The workshop participants were urged to take advantage of existing field campaigns in each polar region, led by people studying current sea ice conditions, to gather further data.
Perhaps the biggest challenge is to synthesize data from different proxy types, often reporting different ice properties, into a single reconstruction. Few multi-proxy comparisons exist, and the meeting participants agreed to set up such a study on some exemplar marine core sections. Despite these problems, reconstructions have been attempted, and the workshop was presented with first efforts at Holocene time slices for both the Arctic and Southern Ocean, and for the last interglacial in Antarctica. Discussion centered on how to improve and enhance these efforts, and how to best report the ice conditions in a way that is compatible both with modern datasets and with the requirements of sea ice modelers. Completion of such work will be the main task for the third workshop, to be held in Bremerhaven, Germany, on 23-25 June 2014.
affiliations
1Department of Earth Sciences, University of Cambridge, UK
2Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
3GEOTOP, Université du Québec à Montréal, Canada
contact
Eric W. Wolff: ew428cam.ac.uk
references
Abram NJ et al. (2013) Quat Sci Rev 79: 168-183
Belt ST, Müller J (2013) Quat Sci Rev 79: 9-25
de Vernal A et al. (2013a) PAGESnews 21(1): 43
Michael Deininger1,2, S. Winterhalder2,3, M. Boyd4,5, K. Braun6,7, Y. Burstyn6,7, L. Comas-Bru8 and A.D. Häuselmann9
Heidelberg, Germany, 28 July - 2 August 2013
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Figure 1: Finding a suitable stalagmite for paleoclimate studies is still one of the most challenging parts of speleothem science. The picture is showing a cave chamber of the Herbstlabyrinth, Germany, which was visited during the S4 field trip. Photo by Simon Mischel. |
Speleothems provide highly resolved and precisely datable paleoenvironmental proxy records with a wide geographic distribution that can capture a range of climatic regimes and their variability over various timescales. Established methods for the analysis of speleothems are constantly being improved, while new methods and proxies are being developed to take full advantage of this unique archive. Henderson (2006) stated: "for paleoclimate, the past two decades have been the age of the ice core. The next two may be the age of the speleothem." And indeed recent years have witnessed an exponential increase in speleothem based climate studies. While speleothem science has developed into an advanced branch of paleoclimate research, no organized training program for young scientists in the field had been developed. Filling this gap was the inspiration behind organizing this workshop, the “1st Summer School on Speleothem Science (S4)”.
The aim of S4 was to bring students and young scientists together from across the globe and provide them with the opportunity to explore in-depth traditional speleothem science methods and receive an introduction to some of the newer developments in the field from established experts. The first summer school of its kind, S4 was organized by a team of PhD students and gathered 46 students from 22 countries.
Over 20 experts gave lectures covering every stage of investigation and analysis of cave environments and speleothems. S4 students were led through the entire process from the first stages of site identification, monitoring, sample characterization and selection, through to complex analytical and statistical data handling. A field trip to Herbstlabyrinth cave system provided an example of ongoing monitoring methods, while hands-on activities including workshops on petrographic analysis, specialized age-modeling software, and statistical analysis gave students the chance to work with real data from their own sites. The evening program of poster sessions and discussion allowed for 36 student projects to receive feedback and advice from peers and experts.
As in many other branches of science, not all researchers and students have analysis facilities at their home institution. Lectures detailing the basics of sensitive analytical procedures and how they apply specifically to speleothems gave many students an excellent overview of the available methods, limitations, costs, locations of labs, and when specific methods are most appropriate. Presentations of commonly used methods provided a platform for discussions regarding known difficulties and how to handle unexpected results. Many experts were on-site for the entire week and actively participated in these discussions providing a wealth of information and troubleshooting strategies.
As with most summer schools and conferences, S4 provided attendees with the valuable opportunity to build networks and make new academic contacts. Lively discussions during the shared lunches and coffee breaks showed that expert participation extended far beyond the classroom lectures. The organizing committee was overwhelmed by the positive feedback which has been received from the participants and experts, and as a result the next S4 is planned for 2016. It will be organized by a "fresh" team of PhD students. We are hopeful that this will establish a tradition of international collaboration and knowledge sharing between young scientists in the speleothem field.
For more detailed information please visit: www.speleothem2013.uni-hd.de
acknowledgements
We thank the University of Heidelberg, PAGES, EGU, the Heidelberg Centre of the Environment (HCE), and the International Association of Sedimentologists (IAS) for their financial and logistic support.
affiliations
1Heidelberg Academy of Science, Heidelberg, Germany
2Institute of Environmental Physics, Ruprecht Karls University, Heidelberg, Germany
3Institute for Geosciences, Johannes Gutenberg University, Mainz, Germany
4Department of Physical Geography and Quaternary Geology, Stockholm University, Sweden
5Bolin Centre for Climate Research, Stockholm, Sweden
6Geological Survey of Israel, Jerusalem, Israel
7Fredy and Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Israel
8UCD School of Geological Sciences, University College Dublin, Ireland
9Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, Switzerland
contact
Michael Deininger: michael.deiningeriup.uni-heidelberg.de
references
Claudio Latorre1,2, P.I. Moreno2,3 and E.C. Grimm4
Olmué, Chile, 12-16 June 2013
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Figure 1: Current South American paleoecological sites in Neotoma. The vast majority of these are part of the constituent Latin American Pollen database. Future collaborations could add much needed faunal data as well as other databases (for figure source code see http://pastebin.com/fgQSVTKb; Image credit: Simon Goring) |
Creating a state-of-the-art database for paleoecological data is an expensive and time-consuming endeavor that requires long-term funding. Currently, no institution in South America is likely to have access to the necessary funding for such an effort. An existing open-access platform, however, now available through the Neotoma Paleoecological Database (www.neotomadb.org) offers an extremely valuable infrastructure that scientists can use throughout the developing world. The use of this common platform would maximize compatibility among the regions and the versatility of this global open access archive of paleoenvironmental data.
Forty-one scientists from seven South American countries gathered in Olmué (located north of Santiago in the foothills of La Campana National Park) for an intense two-day meeting on the policy and practices involved in creating a public-access database for South American paleoecologists. The workshop was followed by a three-day course for young scientists taught by Eric Grimm on how to access and use the Neotoma database, and on how to use the newest versions of the Tilia (pollen analysis; Grimm 1991) and Bacon (age modeling; Blaauw and Christen 2011) applications.
Why Neotoma?
Neotoma is a large, multi-proxy database that includes datasets spanning back to the Pliocene. It is a client-server database housed at the Center for Environmental Informatics at Pennsylvania State University, USA, and is comprised of many virtual databases representing different data types and geographic regions. It arose from a partnership between IT domain scientists and developers in an attempt to answer large-scale questions about paleoenvironmental evolution including climate, fauna and flora.
Workshop participants included archeologists, paleoecologists, zooarcheologists, paleontologists, diatomists, and experts in other paleo fields, who addressed the following questions: (1) How to involve South American scientists in a ground-up effort to build and to contribute to a database? (2) Where can funding be sought to assemble legacy data? (3) Who owns the intellectual rights to the contributions made? (4) What data should be publicly available or restricted (e.g. locations of geographically sensitive sites such as unprotected archeological sites)? (5) Who could act as data stewards for the different South American data types (vertebrates, pollen, rodent middens, zooarcheofaunas, etc.)? (6) Should it be possible to upload unpublished datasets? (7) Should it be possible to upload data to Neotoma for ongoing research projects to take advantage of database analysis and visualization tools but have it embargoed for public release until after publication?
Workshop attendees were divided into breakout groups for further discussion. While recognizing the importance of these large public-access databases, several key concerns need to be addressed, such as data propriety rights. In particular, when dataset authors should be invited to be co-authors on data-synthesis papers and how should the use of data be adequately cited, especially for previously unpublished data. A proposed solution would be to make datasets themselves citable, with for example, a DOI number. This solution could stimulate the publication of legacy data, probably one of the more cost-intensive efforts of creating such a database for South America.
Also, there is the attractive possibility of creating “embargoed” contributions, i.e. datasets uploaded to Neotoma but not publicly available for a determined amount of time. This would allow time to take advantage of the database’s infrastructure and ample time to publish an article before releasing data. Other important aspects discussed included how to create “fuzzy” coordinates for geographically sensitive sites, in which only the data contributors and relevant land management agencies know the actual locations (e.g. to protect sites from looting).
Clearly much work lies ahead, but researchers were enthusiastic about the possibility of generating a public database which could address and generate new and exciting research questions, particularly those associated with broad-scale climate and land-use change that could contribute to published data and incorporate the vast quantity of legacy data generated in South America for over a century.
affiliations
1Department of Ecology, Pontifical Catholic University of Chile, Santiago, Chile
2Institute of Ecology and Biodiversity, University of Chile, Santiago, Chile
3Department of Ecological Sciences, University of Chile, Santiago, Chile
4Illinois State Museum, Springfield, USA
contact
Claudio Latorre: clatorrebio.puc.cl
references
Blaauw M, Christen JA (2011) Bayesian Anal 6: 457-474
Grimm EC (1991) Tilia and Tiliagraph. Illinois State Museum, Springfield