PAGES Magazine articles
Veerle Vanacker1 and Thomas Hoffmann2
2nd GloSS Workshop, Louvain-la-Neuve, Belgium, 30 January - 1 February 2017
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Figure 1: Overgrazing reducing infiltration and accelerating runoff and soil erosion in the Northern Andes. Gully systems and landslides are the major contributors of sediment to the fluvial system. Credit: Veerle Vanacker, July 2013 |
Anthropogenic soil erosion causes soil degradation, reduces soil productivity (Fig. 1), compromises freshwater ecosystem services and drives geomorphic and ecological change in rivers and their floodplains (Anthony et al. 2014; Wang et al. 2016). Despite our knowledge of the fundamental mechanistic processes of soil erosion, transport and deposition and the control of climate, soil erodibility, topography, and land use and management on soil and sediment transfers, the rich variety of past land use and human settlement patterns worldwide implies that global patterns of anthropogenic soil erosion and fluvial sediment transfer remain poorly understood (Vanacker et al. 2014).
We need better global assessments of anthropogenic soil erosion and the consequent transfer and storage of sediment to the coastal zones to reduce the societal impact of human-accelerated erosion. The PAGES Global Soil and Sediment transfers in the Anthropocene (GloSS) working group aims to build a comprehensive global database on soil and sediment transfers in the Anthropocene, to identify hotspots of soil erosion and sediment deposition in response to human impacts, and locate data-poor regions as strategic foci for future work. To achieve this aim, 39 participants from 15 countries with expertise in soil erosion assessments, erosion modeling, human-landscape interactions and global sediment fluxes attended the meeting.
The first part of the meeting was dedicated to oral and poster presentations, including 11 keynotes and smaller topical presentations on anthropogenic sediment fluxes, human-climate interaction on river systems and sediment fluxes, and temporal changes in sediment budgets for lakes and floodplains from various regions of the world. Major focus was given to the coverage of GloSS-related studies on each continent and regarding the various environments considered for the GloSS database (i.e. hillslope, river channels, floodplains, lakes and deltas). The second part of the workshop was entirely dedicated to breakout group discussions, where the workshop participants revised the GloSS database structure and discussed standard operating procedures for data-submission and internal procedures for server-side data cleaning and quality control. Participants agreed that the GloSS database should focus on a limited number of proxies/indices that are widely available: (1) sediment loads (e.g. Syvitski and Kettner 2011), (2) sedimentation rates (Yang and Lu 2014), (3) cosmogenic radionuclide denudation rates (e.g. Portenga and Bierman 2011), and (4) erosion rates (e.g. Maetens et al. 2012). For each of the four proxies/indices, a breakout group revised and improved the metadata structure, and defined parameters or variables that need to be included, their format, unit of measurement, quality control, and spatial and temporal integration. Group members reviewed the criteria, which have now been included in a comprehensive data dictionary.
The group also updated the GloSS roadmap for two primary products to be completed before the end of the project in 2017. Based on the GloSS database, we plan to produce a global overview map of the availability of proxies and indices to quantify soil and sediment transfers throughout the Holocene. The group also discussed how to take advantage of the expertise gained from highly detailed case studies worldwide, and proposed to work towards a review paper on erosion and sedimentation issues in the Anthropocene to increase awareness on the topic.
The GloSS working group held a brief gathering in May 2017, during the 5th PAGES OSM meeting in Zaragoza, Spain, to discuss progress. More information is available on the PAGES website.
The workshop was co-organized by the Université catholique de Louvain, University of Leuven and Université de Liège, Belgium. Funding was provided by PAGES and the Belgian Fonds de la Recherche Scientifique (FNRS).
affiliationS
1Earth and Life Institute, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
2German Federal Institute of Hydrology, Koblenz, Germany
contact
Veerle Vanacker: Veerle.vanacker
uclouvain.be
references
Anthony EJ et al. (2014) Earth Sci Rev 139: 336-361
Maetens W et al. (2012) Prog Phys Geogr 36: 599-563
Portenga EW, Bierman PR (2011) GSA Today 21: 4-10
Syvitski JPM, Kettner A (2011) Phil trans R Soc A 369: 957-975
Vanacker V et al. (2014) Landsc Ecol 29: 293-309
Keely Mills1, P. Gell2 and J. Saros3
Bangor, USA, 26-28 April 2016
The second meeting of PAGES’ Aquatic Transitions working group, held at the University of Maine, was attended by 23 members, including 16 new representatives from the UK, US, Canada, India, and Argentina. Given the number of new faces at the meeting, the workshop opened with short introductory presentations from the new participants, leading nicely into a recap on the outcomes and updates from the previous meeting in 2015 (Mills and Gell 2015).
Updates were also provided on a number of manuscripts currently in preparation. The manuscript “Modeling regime shifts in lake sediments” (led by Z. Taranu and M. Perga) stimulated much discussion among new members, and S. Juggins and G. Simpson provided fantastic statistical guidance with regards to the identification of “transitions” in paleolimnological archives. The review paper, by 24 members of the working group and led by N. Dubois, titled “Early human impacts of lakes and wetlands” is a large undertaking. The authors present at the meeting worked on the draft, the focus of the conclusions, and proposed additional sections to ensure a global perspective.
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Figure 1: Identifying transitions in lake sediment sequences is complex, not least because both climate and humans can cause changes in lake systems that manifest in a similar fashion in the lake sediment archive. Reprinted from Mills et al. (2017) with authorization from BGS © NERC 2017. |
Prior to the workshop, K. Mills and P. Gell were invited by “Wiley Interdisciplinary Reviews (WIREs): Water” to write an overview paper on long-term changes in lake systems. We used this meeting as a sounding board for ideas and inputs, and outlined the now-published paper “Deciphering long-term records of natural variability and human impact as recorded in lake sediments: a palaeolimnological puzzle” which is co-authored by 15 members of the Aquatic Transitions community (Mills et al. 2017; Fig. 1).
J.-P. Jenny led a discussion on the content and nature of the data required to achieve the goals of Aquatic Transitions, and whether the overlap with other core working groups’ databases (from PAGES 2k Network or the former Varves Working Group, for example) was an impetus for a joint effort, as opposed to “reinventing the wheel” for similar data collection.
Other key outputs from this meeting included the outline of a book proposal for the Springer series “Developments in Paleoenvironmental Research”, in response to an invitation from the publisher. A session proposal was also written and submitted to the International Association for Ecology’s (INTECOL) International Wetlands Conference (IWC) that was held in Changshu, China, in September 2016. This conference was a fantastic opportunity to broaden the membership of Aquatic Transitions in South East Asia, and the conference also opened up the opportunity to engage with key stakeholders (including Ramsar, catchment managers and other practitioners in water management). S. McGowan and K. Mills, who attended this meeting, wrote a report for the British Geological Survey’s blogsite “Geoblogy” (McGowan and Mills 2016). The success of the INTECOL IWC session led to the next Aquatic Transitions meeting in Malaysia in February 2017, which focused on enhancing the understanding of freshwater systems in SE Asia.
affiliationS
1British Geological Survey, Keyworth, UK
2Water Research Network, Federation University Australia, Ballarat, Australia
3Climate Change Institute, University of Maine, Bangor, USA
contact
Peter Gell: p.gellfederation.edu.au
references
McGowan S, Mills K (2016) INTECOL International Wetlands conference in Changshu, China. Geoblogy
Xianyong Cao1, U. Herzschuh1, M.-J. Gaillard2, K. Morrison3 and Q. Xu4
Shijiazhuang, China, 6-11 March 2017
This workshop and related training course were held at Hebei Normal University in Shijiazhuang, China, and organized within the activities of PAGES’ working group LandCover6k. The major aim was to gather the coordinators of the LandCover6k working sub-group Asia-Oceania, experts in the field of quantitative pollen-based vegetation reconstruction, and data contributors (pollen, archaeology, history). The purpose was to (i) explain and discuss the objectives and research strategies of LandCover6k, (ii) assess the availability of fossil pollen records and pollen data archives/databases, pollen productivity estimates (parameters needed for pollen-based quantitative estimates of plant cover), and archaeological and historical data, and (iii) plan the future activities necessary to achieve the objectives of LandCover6k in Asia-Oceania. Following a win-win collaborative approach during the workshop, an intensive training course was held on the methodological tools for pollen-vegetation modeling and calculation of pollen productivity estimates. The course also included instruction on upscaling of archaeological data to a global scale land-use scheme. Anthropogenic land-cover-change modeling was provided to the data contributors to facilitate the achievement of the LandCover6k objectives, and data contributors were encouraged to use those methodological tools for their own scientific questions. The workshop was attended by 83 participants including 63 Chinese and Indian young scientists and students.
The four major outcomes of the workshop are:
(i) An evaluation of spatial pollen-based reconstructions of vegetation cover and climate, and discussion on their interpretation and reliability issue.
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Figure 1: Extension of the Eastern continental Asia pollen dataset to North Asia, with 199 newly added fossil pollen records and 3943 modern pollen data. In total, the dataset now includes 470 fossil and 6569 modern pollen data. |
(ii) Discussion on the status and availability of databases for pollen records in Eastern Asia. In particular, X Cao and U Herzschuh presented an extension of Eastern continental Asia pollen dataset (Cao et al. 2013; 2014) to Siberia (Fig. 1), and Jian Ni presented the development of a new version of the Chinese Quaternary Pollen Database.
(iii) The launch of the State Key Program of National Natural Science Foundation of China “Quantitative pollen-based land-cover reconstruction (1°×1°) for the purpose of climate modeling in China since 6 ka” coordinated by Q Xu, which includes studies of pollen productivity estimates in all major vegetation and climate zones of China and pollen-based reconstructions of past vegetation cover using REVEALS model (Sugita 2007).
(iv) Teaching and dissemination of methods, tools and strategies for pollen-data handling (e.g. the R program and packages for statistical computing), pollen-based climate and vegetation reconstructions (e.g. weighted averaging partial least squares WA-PLS, modern analogue technique MAT), calculation of pollen productivity estimates (ERV model), pollen-based reconstruction of vegetation cover (REVEALS and LOVE models), and land-use inference from historical and archaeological data.
By regularly following up on the four outcomes above, we expect that the workshop will result in a higher number of scientists in Eastern Asia who will (i) contribute new pollen productivity estimates for the major plant taxa characteristic for that region and (ii) submit fossil pollen records to international pollen archives and databases. This process will significantly improve the requirements for reliable reconstructions of past anthropogenic vegetation cover in Eastern Asia for the purpose of LandCover6k’s goals.
affiliationS
1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Research Unit Potsdam, Germany
2Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden
3Department of Anthropology, University of Pennsylvania and Museum of Archaeology and Anthropology, Philadelphia, USA
4College of Resources and Environment Sciences, Hebei Normal University, Shijiazhuang, China
contact
Xianyong Cao: Xianyong.Caoawi.de
references
Cao X et al. (2013) Rev Palaeobot Palynol 194: 21-37
Sonia L. Fontana1, T. Giesecke1, P. Kuneš2 and M.-J. Gaillard3
Salvador de Bahia, Brazil, 29-31 October 2016
Latin America is an important region for the understanding of the global climate system as it extends from the northern hemisphere into the high southern latitudes. Few synoptic studies are available for this continental space. The purpose of this workshop was to bring together Latin American researchers working on past vegetation reconstruction to better integrate the local scientific community into the activities of the PAGES LandCover6k working group (Gaillard et al. 2015). Scientifically, a strong focus was to stimulate participants to attempt quantitative reconstructions and providing them with the tools to do so. The meeting attracted 22 scientists at all career stages, from Mexico, Colombia, Brazil, Bolivia, Argentina, Russia and Germany.
The workshop provided an overview of available methods for pollen-based reconstruction of land cover with emphasis on the Landscape Reconstruction Algorithm, including the REVEALS and LOVE models (Sugita 2007). Lectures also addressed the parameters required for these applications, including the need to estimate relative pollen productivity for selected plant taxa of interest, as well as the fall speed (settling velocity) of the respective pollen types. Validation and application of these models were illustrated through studies in Europe, North America and China. The modern analogue technique was discussed as an alternative way to obtain quantitative estimates of the cover of major vegetation units, such as woodland and open land, without the need of a detailed understanding of the pollen-vegetation relationship. However, modern analogue techniques need a large number of surface sediment samples representing good modern analogues of past vegetation, which is problematic in Latin America due to very recent and drastic land-cover change. The training course followed the path from vegetation surveys and estimating relative pollen productivities to their application in REVEALS-based reconstructions of past plant cover.
Discussions focused on the application of these approaches to the diverse ecosystems of Latin America that have their unique challenges for pollen-based quantitative vegetation reconstructions. Estimating the taxon-specific production and dispersal of pollen is crucial for a better understanding of the results portrayed in pollen diagrams and builds the basis for quantitative reconstructions. This type of investigation is scarce in Latin America and a challenging task, in particular in tropical and subtropical environments with high plant diversity. First attempts aiming to estimate pollen productivity and dispersal in southwest Amazonia and at the forest-steppe ecotone in Patagonia were presented and discussed.
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Figure 1: Human land use at the forest-steppe ecotone in northern Patagonia. Rumex acetossella (red color in the grazed land) commonly known as sheep's sorrel or red sorrel, is a major anthropogenic indicator of animal-based disturbance activities occurring during the last few hundred years. |
While LandCover6k aims to quantify human-induced changes in land cover, Latin America contains different environments where the proportion of woodland versus grassland has changed during the Holocene due to shifts in precipitation and temperature, namely the upper mountain forest versus páramo vegetation in the Andes mountains, the forest grasslands in the Llanos Orientales, the Mata Atlântica in Brazil, and the forest-steppe ecotone in Patagonia. However, these ecosystems were also preferred by humans that controlled the encroachment of forest with fire. Therefore, the effects of human action and climate change are often difficult to disentangle (Fig. 1).
Databases are an important prerequisite for larger synoptic studies. The Latin American Pollen Database and new tools available through the Neotoma Database were presented and discussed. Plans were made to develop a modern surface-sample pollen dataset and set up projects which aim to achieve pollen-based reconstructions of plant cover in the past.
This workshop was organized in collaboration with the XIV International Palynological Congress, the Federal University of Bahia and local colleagues, Francisco Hilder Magalhães e Silva, Paulino Pereira Oliveira, Vivian Jeske-Pieruschka, Kelly Regina Batista Leite, and Lázaro Benedito da Silva.
Further details about LandCover6k and this workshop can be found at pastglobalchanges.org/landcover6k
affiliationS
1Department of Palynology and Climate Dynamics, University of Göttingen, Germany
2Department of Botany, Charles University, Prague, Czech Republic
3Biology and Environmental Science, Linnaeus University, Kalmar, Sweden
contact
Sonia Fontana: Sonia.Fontanabiologie.uni-goettingen.de
references
Marie-José Gaillard1, P. Gonzales2, S. Harrison3, K. Klein Goldewijk4, F. Li1 and M. Madella5
LandCover6k General Workshop, Zaragoza, Spain, 16-17 May 2017
The LandCover6K working group (Gaillard et al. 2015) met for its third yearly general workshop. The focus was on how the quantitative land-use and land-cover reconstructions achieved so far should be synthesized and formatted to be useful for (i) climate and dynamic vegetation modeling studies, and (ii) evaluation and improvement of scenarios of past anthropogenic land-cover change (ALCC). Introductory presentations by S. Harrison on CMIP6-PMIP4 (climate/paleoclimate modelling intercomparison programs); A. Dallmeyer on a new ensemble of transient model simulations of vegetation change performed in MPI-ESM1.2 using different forcings (e.g. land use); B. Stocker on recent modeling results of CO2 emissions from ALCC estimated using global dynamic vegetation models forced by scenarios of the extent of past anthropogenic land use (Stocker et al. 2017); K. Klein Goldewijk on the latest version of HYDE 3.2 (Klein Goldewijk et al. 2016); E. Ellis on the concepts of anthrome, sociocultural niche construction and anthroecological change, and the GLOBE project; and M. J. Gaillard (global land cover), M. Madella (global land use), U. Lombardo and W. Gosling (Latin America), A. Kay and C. Courthey-Mustaphi (Africa), M. Chaput (Canada), S. Teng (China), and J. Bunting (pollen productivity estimates) on the major progress made in studies of pollen productivity estimates and land-cover/land-use reconstructions in the world provided the necessary background to formulate and plan LandCover6k products.
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Figure 1: Examples of REVEALS estimates of plant cover (in proportion for an area >100x100 km) over the Holocene for five plant taxa and three taxa groups in the temperate steppes zone of China (purple on map). Each diagram represents the results from REVEALS runs using pollen records from several sites: (A) 1 bog (black) and 2 lakes (blue); (B) 3 lakes. V: Cool mixed forest, temperate broad-leaved forest, i.e. Fraxinus, Quercus, Tilia, Ulmus, and Rosaceae. VI: Warm temperate forest and tropical forest, i.e. in those reconstructions only Rubiaceae. VII: Cultivated land, temperate grassland, tundra, and desert taxa, i.e. Artemisia, Asteraceae, Brassicaceae, Caryophyllaceae, Castanea, Chenopodiaceae, Convolvulaceae, Fabaceae, Cannabis/Humulus, Juglans, Lamiaceae, Liliaceae, Polygonaceae, and Ranunculaceae. Data by Furong Li (pers. comm.; see also Li 2016). |
Pollen-based REVEALS reconstructions of plant cover exist for Europe (Trondman et al. 2015), temperate China (Li 2016; Fig. 1), and Siberia (X. Cao and U. Herzschuh, unpublished). Reconstructions for North America, Canada and Alaska are in progress, as well as studies on pollen productivities and REVEALS reconstructions in SE India and West Africa. Land-use maps are ready for Northern and Central America and the implications for the HYDE scenarios and effects on climate have been evaluated. The land-use maps for West Africa (A. Kay et al.) and a major synthesis of pollen data, archaeological and historical data for East Africa (R. Marchant et al.) were finalized. The process of gathering archaeologists and historians in Europe, Latin America, India and China has been successful. The LandUse6k community is now ready to achieve land-use mapping at the global scale in the coming few years.
Four LandCover6k products are currently in progress:
1. Gridded (1°x 1°) pollen-based REVEALS estimates of plant cover in the northern hemisphere (>40°N) for five time windows of the Holocene based on the available REVEALS estimates in northern America, Canada, Alaska, Europe, Siberia and China.
2. A comparison at a 1°x 1° grid spatial resolution and 500 years’ time resolution over the last 8 ka between (i) the plant cover obtained from the transient runs presented by A. Dallmeyer and (ii) the plant cover obtained from pollen data using the REVEALS model (Marquer et al. 2017).
3. A comparison at 1°x 1° resolution for Europe of the fraction of deforested land as estimated by the ALCC scenarios of HYDE 3.2 and the pollen-based REVEALS estimates of the cover of openland for five time windows of the Holocene (see 1. above).
4. A new set of multi-model land C cycle simulations covering the Holocene using LandCover6k-improved ALCC scenarios (Stocker, see above).
The “products” 1-2 above and a roadmap for the model-intercomparison study (product 4) will be presented at the 1st PMIP4 conference in Stockholm in September 2017 (www.pmip2017.se).
affiliationS
1Department of Biology and Environmental Science, Linnaeus University, Kalmar, Sweden
2Department of Geo-environmental Processes and Global Change (CSIC), Pyrenean Institute of Ecology, Zaragoza, Spain
3Centre for Past Climate Change, School of Archaeology, Geography and Environmental Science, University of Reading, UK
4Copernicus Institute of Sustainable Development, Utrecht University, The Netherlands
5Department of Humanities and ICREA, Universitat Pompeu Fabra, Barcelona, Spain
contact
Marie-José Gaillard: marie-jose.gaillard-lemdahllnu.se
references
Gaillard M-J et al. (2015) PAGES Mag 23(1): 38-39
Klein Goldewijk K et al. (2016) Earth Syst Sci Data Discuss
Marquer L et al. (2017) Quat Sci Rev 171: 20-37
Alistair Seddon1, L. Cole2,3, M.-S. Fletcher4, J. Morris5, K. Willis6,2 and EcoRe3 working group
EcoRe3 workshop, Finse, Norway, 27-31 March 2017
The aim of the first EcoRe3 working group workshop was to develop novel, quantitative approaches to measure components of ecosystem resilience (e.g. resistance - the amount of change following a disturbance; recovery rates - the speed of recovery following disturbance; and latitude - the distance to an ecological threshold) using proxy data from lake and bog sediments. It was attended by 23 participants from 11 countries, and was split into three main thematic sessions. The workshop also included a meeting to discuss working group organization over the next three years. It was co-funded by PAGES and the Research Council of Norway.
Session one built on preliminary work which used a variety of statistical approaches to measure resistance and recovery rates in pollen data. A key issue highlighted in discussions was that the timing and the impact of disturbance events are represented by a small number of data points in many Holocene sediment sequences. Numerical techniques which can identify signal from noise are therefore crucial for quantifying any disturbance-related ecological change in such records.
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Figure 1: Example of resilience components estimated from pollen data (black dots). |
Two new projects were established which aim to address this issue using different approaches. First, a systematic review will be used to investigate current knowledge about the timing and magnitude of ecological disturbances in different systems. The result of this work will lead to a series of recommendations that highlight the appropriate analyses and ecological questions for any given paleo-dataset. Second, a series of model-based, statistical approaches were developed to enable robust detection and quantification of any disturbance-related response. Members of EcoRe3 are now working to implement these model-based approaches in a range of ecological settings (Fig. 1).
Since a number of workshop participants were experts in measuring components of resilience using remote sensing data, a second session was dedicated to exploring methods of measuring biome stability, determining the number and presence of alternative states, and identifying distances to thresholds using a combination of both spatial and temporal datasets. A novel statistical approach was presented to address these aims using satellite data, and breakout discussion groups were held in which this method was subjected to rigorous critique and review. Discussions were then held to determine pathways for translating the approach, currently developed for univariate satellite data, to a large spatial network of paleoecological records.
Finally, a third session aimed to predict which functional traits (i.e. morphological, physiological or phenological characteristics that influence how organisms respond to the environment; Diaz et al. 2013) would be responsible for ecosystems with high resistance, and which traits would be related to fast recovery rates. From a paleoecological perspective, it was clear that the key challenge is to develop tools which enable one to move from pollen assemblages (with their known biases related to taxonomic resolution and representation) to species-based trait databases derived from present-day ecological understanding and sampling (e.g. the TRY database; Kattge et al. 2011). This would then allow predictions made by ecological trait theory to be tested using paleoecological data. A workshop which aims to tackle these issues is planned in Utah, USA, in 2018.
During the workshop, a number of participants gave talks on their own methods to identify alternative stable states and early warning indicators in long-term ecological data. A critical theme that ran throughout the discussions was the need to have an underlying model to support the assumptions of resilience theory, since abrupt changes are not necessarily always associated with fold bifurcations (e.g. Williams et al. 2011). During the EcoRe3 working group meeting, we distributed work tasks amongst members of the group, identified milestones for papers, and established the topics, timings and locations of future meetings. The spectacular Finse Alpine Research Station meant that many participants were able to try their hand at cross-country skiing as an antidote to the intense discussions over the course of the week. Further details of EcoRe3 activities will be published on the website (pastglobalchanges.org/science/wg/ecore3/intro) and on social media outlets (see below).
- EcoRe3 on Facebook (visit page and request to join): https://www.facebook.com/groups/286999515057710/
- EcoRe3 on Twitter: @Eco_Re3
- EcoRe3 on ResearchGate: https://www.researchgate.net/project/EcoRe3-Resistance-Recovery-and-Resilience-in-Long-term-Ecological-Systems-2
affiliationS
1Department of Biology, University of Bergen, Norway
2Rezatec Ltd, Harwell, UK
3Department of Zoology, University of Oxford, UK
4School of Geography, University of Melbourne, Australia
5Department of Geography, University of Utah, Salt Lake City, USA
6Royal Botanic Gardens, Kew, London, UK
contact
Alistair Seddon: Alistair.Seddonuib.no
references
Díaz S et al. (2013) Ecol Evol 3: 2958-2975
Mike Evans1, H. Goosse2 and S. Khatiwala3
Louvain-la-Neuve, Belgium, 29 May - 1 June 2017
Data assimilation (DA) for paleoenvironmental reconstruction combines information from observations and models of the Earth system to develop mechanistically consistent estimates of environmental fields. There are four essential ingredients to paleoenvironmental DA: (1) Models of the Earth system describing possible system states; (2) Observations telling us what actually happened in the real world; (3) Proxy System Models (PSMs) describing how geological, biological or chemical archives are imprinted with environmental signals, and linking process models to observations; and (4) An algorithm that optimally combines model results, observations, and uncertainties in the various elements.
To review current activities in paleoenvironmental DA, a group of climate scientists recently met in Louvain-la-Neuve, Belgium. The group contained specialists of climate modeling and scientists more closely involved in the collection and analysis of paleoclimate observations. The goal was to consider challenges and potential for advances in DA and PSMs, and to stimulate new activities via practical training exercises.
Challenges and opportunities
Overview talks first reviewed the activities of a small but rapidly growing community. The parallels with modern DA were particularly inspiring. In addition to the product itself, reanalyzes are an opportunity to bring together scientists of different backgrounds, stimulate data recovery, and demonstrate skill improvement brought by additional data.
The talks and subsequent breakout groups identified many existing PSMs of varying structure and complexity for a number of major paleoenvironmental archives and observations. However, the uncertainty in PSMs – structural and/or systematic – is not well constrained. There are also multiple DA techniques that might be applied to paleoenvironmental reconstructions but no assessment of their relative advantages and limitations in settings corresponding to paleoclimate applications is currently available. Therefore, the choice of PSM for a particular DA problem is frequently unclear.
The workshop concluded with four classroom exercises introducing participants to proxy system modeling, adjoint methods and data assimilation.
Recommendations of the workshop
The participants proposed three activities to be launched in the coming months:
(1) Use case studies for particular replicated observations, proxy systems and archives to better describe the structural uncertainty and systematic error in PSMs and in observations as it seems important to first test the PSM independently of Earth system models.
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Figure 1: Example of the data distribution for the comparison of data assimilation methods, derived from the data distribution in 1500 CE in the PAGES 2k database (PAGES 2k Consortium 2017). Figure courtesy of J. Franke. |
(2) Create a testbed for the development and testing of paleo DA methods constrained by a realistic observing network corresponding to the past millennium, but using data for the last century with specific additional noise (Fig. 1), and compare the reconstructions to modern reanalysis products.
(3) Form a task force to explore uncertainty quantification procedures relevant to paleoclimate reconstructions, develop metrics to assess their relative merits, and to apply these to parameter estimation and data assimilation problems.
As a first step, the proposed activities are thus either devoted to the modeling of a specific type of record or to the comparison of DA methods in an idealized framework where observations are modeled variables with a precisely known uncertainty. First results of these activities are expected in early 2018 so that they can be presented at a planned DAPS session at EGU. As the ultimate goal of DAPS is to bridge the gap between modeling of a wide range of data and data assimilation, the next DAPS workshop in the second half of 2018 will be devoted to issues that limit a global approach and the means to tackle them. The path to solve those problems will be put forward in 2019.
DAPS is an open community of observationalists and modelers, and we invite you to bring your interests and expertise into the project. For more information, visit the DAPS website (pastglobalchanges.org/science/wg/daps/intro) where the experimental design of the planned intercomparisons will be posted, join the working group mailing list (https://listserv.unibe.ch/mailman/listinfo/daps.pages) or email one of the coordinators.
A copy of the talks presented at the workshop is available here: pastglobalchanges.org/calendar/2017/127-pages/1657-daps-1st-wshop-2017
affiliationS
1Department of Geology, University of Maryland, College Park, USA
2Earth and Life Institute, Université catholique de Louvain, Belgium
3Department of Earth Sciences, University of Oxford, UK
contact
Mike Evans: mnevansumd.edu
references
Emilie Capron1,2, N. Vázquez Riveiros3, F. He4,5, A. Jacobel6 and X. Zhang7
Montreal, Canada, 18-20 October 2016
The second QUIGS workshop brought together 28 delegates to assess current knowledge and research needs on the spatio-temporal patterns of climate forcing, responses and feedbacks that characterize glacial terminations, i.e. transitions between glacial and interglacial periods.
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Figure 1: Terminations I (TI), II (TII) and V (TV) forcing and climatic parameters. (A) Orbital and (B) greenhouse gas forcing (Bereiter et al. 2015; Loulergue et al. 2008), together with records of (C) ice rafted debris, (D) Asian Monsoon intensity (Cheng et al. 2016), and (E) Antarctica air temperatures (Jouzel et al. 2007). TI: NA87-27 records (Waelbroeck et al. 2001), TII and TV: ODP-980 records (McManus et al. 1999); Transient surface temperature modeled with CCSM3 are shown in yellow (He et al. 2013). Temperature records represent anomalies relative to the last millennium. Grey bars indicate intervals characterized by substantial North Atlantic IRD deposition and weak Asian Monsoon. |
Presentations and discussions outlined common features and differences between terminations. Similarities include nonlinear, multi-millennial scale changes in key climatic indicators, e.g. decreased global ice volume, atmospheric greenhouse gas concentration rise, surface temperature increases and Asian monsoon intensification. However, amplitude and duration of terminations are variable. Transitions initiate at various glacial ice sheet states and progress under a variety of orbital forcing scenarios (Fig. 1).
Numerous presentations evidenced increased record availability and understanding for Terminations I (TI) and II (TII). However, results from the low latitudes (Africa, South America) and outside the North Atlantic basin (Pacific, Southern Ocean) highlighted regional variability, emphasizing the need for further constraints and careful interpretation in less-explored regions.
Millennial-scale events are a crucial part of the dynamics of terminations. Terminations include periods characterized by Ice-Rafted Debris (IRD) deposition in the North Atlantic under Heinrich Stadial-like conditions (Fig. 1), likely associated with substantial Atlantic Meridional Overturning Circulation (AMOC) weakening. Each termination seems to feature a sharp increase in CH4 and in Asian monsoon strength, coinciding with the end of the main CO2 and Antarctic temperature increases. Evidences indicating sub-millennial-scale changes occurring at high and low latitudes in association with Heinrich Stadials (HS) 1 and 11 are increasing. Although millennial-scale investigations across older terminations are emerging, records are still scarce, and many have insufficient resolution to allow identification of abrupt climate changes.
Establishing the deglacial sequence, its regional fingerprint and the phasing with respect to orbital forcing beyond TI and TII requires paleoclimatic records of higher temporal resolution and improved chronologies, especially since the fingerprint of the Younger Dryas cooling and Bølling warming across TI does not appear as a consistent feature of older terminations. New ice core absolut age markers and precise radiometric dates on Asian speleothems (Cheng et al. 2016), now available for the last 700 ka, will represent useful anchors to improve paleoclimate record chronologies.
Modeling results were also a key part of the discussions. Initiatives by several climate modeling groups provide a dynamic framework to explain TI millennial-scale events (Fig. 1) and exploratory simulations for TII are in progress. A QUIGS paper in preparation will provide a framework and recommendations for the upcoming TII transient simulations. This effort will complement the TI deglaciation experiments of PMIP4, allowing an evaluation of the similarities and differences in the climate system response during TI and TII in concert with paleoclimate records.
Constraining the size and spatial distribution of ice sheets during the penultimate glacial maximum remains a challenge. New data will complement recent modeling efforts to describe the interaction between insolation and ice sheets and its role in pacing terminations. The proposed statistical models of orbitally driven terminations raised questions on the role of insolation during “failed” terminations. Further constraints are also required on the glacial carbon reservoir, and the mechanisms responsible for its modification across T1 remain debated.
The next QUIGS workshop focussed on interglacials of the 41 ka-world and the Middle Pleistocene Transition. It took place 28-30 August 2017 on the Greek island of Lesvos.
acknowledgements
NVR acknowledges funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013 Grant agreement n° 339108).
affiliationS
1British Antarctic Survey, Cambridge, UK
2Centre for Ice and Climate, University of Copenhagen, Denmark
3Laboratoire des Sciences du Climat et de l’Environnement, Université Paris-Saclay, Gif-Sur-Yvette, France
4Center for Climatic Research, University of Wisconsin-Madison, USA
5College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, USA
6Columbia University, Lamont-Doherty Earth Observatory, New York, USA
7Alfred Wegener Institute, Bremerhaven, Germany
contact
Emilie Capron: capronnbi.ku.dk
references
Cheng H et al. (2016) Nature 534: 640-646
Bereiter B et al. (2015) Geophys. Res. Lett.: 42, doi:10.1002/2014GL061957
He F et al. (2013) Nature 494: 81-85
Jouzel J et al. (2007) Science 317: 793-796
Loulergue L et al. (2008) Nature 453: 383-386
Erin L. McClymont1, A.M. Haywood2 and A. Rosell-Melé3
PlioVAR meeting, Durham, UK, 19-21 April 2017
The aim of the PlioVAR working group is to develop a synthesis of our understanding of late Pliocene climate variability over glacial-interglacial timescales. Twenty-four researchers met to discuss progress in the synthesis of existing multi-proxy data sets from marine sediment archives, and to finalize agreement on common protocols for the reporting and compilation of data.
The Durham meeting started with presentations outlining PlioVAR aims and objectives, reporting progress towards regional data assimilation, and discussing appropriate data management. A white paper on potential stratigraphic protocols by Marci Robinson and Tim Herbert was outlined and discussed. An update on ongoing efforts by the inter-linked Pliocene Model Intercomparison Project (PlioMIP) was provided.
The remainder of the workshop focused on identifying the following three priorities:
1. Continued data collection from marine sediment cores for late Pliocene climate (ca. 2.4-3.6 Ma)
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Figure 1: Ongoing data synthesis of late Pliocene climate variability, from the North Atlantic and Nordic Seas. Top, LR04 global benthic stack with the targeted Marine Isotope Stage M2 to KM3 interval (grey shading) and paleomagnetic timescale. Bottom, compilation of sea surface temperature records between 3.40 and 3.00 Ma. PlioVAR will characterize the glacial-interglacial variability in these records across multiple proxies, and compare it to the intensification of northern hemisphere glaciation around 2.4-2.8 Ma. Source: De Schepper S, Ho SL and Risebrobakken B (unpublished). |
During the northern summer, the regional synthesis leaders will continue to collate multi-proxy datasets. It was agreed that this information should not be restricted to sea-surface temperatures, but span a range of climate variables where information is available. There was discussion around how to compare single-proxy and multi-proxy sites, how to handle potentially conflicting signals in multi-proxy sites, and how to represent uncertainties which are not always quantifiable. The two PlioVAR target intervals focus on (i) 2.4-2.8 Ma, to represent the intensification of northern hemisphere glaciation, and (ii) the marine isotope stages M2-KM3 interval (ca. 3.30-3.15 Ma), which marks a glacial-interglacial transition and had an orbital configuration similar to modern (Fig. 1). Between 20 and 30 key marine sites have been identified which will contribute to the PlioVAR synthesis. However, the heterogeneity of data availability across regions was highlighted. The highest number of sites are found in the North Atlantic (Fig. 1), whereas other regions have fewer sites represented. It was noted that recent International Ocean Discovery Program (IODP) expeditions will address some of these gaps (e.g. Expedition 353 Indian Monsoon, Expedition 354 Bengal Fan, Expedition 355 Arabian Sea Monsoon, Expedition 356 Indonesian Throughflow, Expedition 361 Southern African Climates).
2. Evaluation of stratigraphic controls
A set of minimum standards was developed for the acceptance of datasets into the PlioVAR synthesis. Existing age models will be reviewed, and revised if required. It was recognized that there could be differences in the resolution of temporal control and the resolution of the proxy data, and the procedures for handling this were discussed.
3. Continued population of the PlioVAR database
An interactive database which displays PlioVAR sites was shown, and will soon be launched. This resource will allow working group members to identify whether their own published or emerging datasets are missing from the current synthesis. For the data synthesis effort, a dataset template was agreed upon, which the leaders for each region will use, facilitating the statistical analysis required to investigate climate variability.
PlioVAR will continue to work on synthesis efforts over the next few months, and we welcome new participants to those activities. We are interested to learn of emerging data which might contribute to our planned assessment of glacial-interglacial variability within the two intervals detailed above. More information will be transmitted through the PAGES website and via the working group mailing list (pastglobalchanges.org/science/wg/former/pliovar/intro). The Steering Committee chair can also be contacted directly (erin.mcclymontdurham.ac.uk).
acknowledgements
We thank PAGES, the Leverhulme Trust, and Durham University for the funding support which made this meeting possible.
affiliations
1Department of Geography, Durham University, UK
2School of Earth & Environment, University of Leeds, UK
3ICREA and Universitat Autònoma de Barcelona, Spain
contact
Erin McClymont: erin.mcclymontdurham.ac.uk
Hubertus Fischer1, A.C. Mix2 and K.J. Meissner3
Bern, Switzerland, 5-7 April 2017
“Understanding past climate variations plays a critical role in improving predictions for the future.”
“The short time interval of direct observations hampers our understanding of climate variability and planetary boundaries but paleoscience can overcome this limitation.”
“The study of warmer time periods in the past will improve our understanding of climate/greenhouse gas feedbacks.”
or “The past is the key to the future.”
Statements like these are used in many paleoscience publications and often found in funding proposals. But what knowledge can we really gain on the changes our planet will experience in a 1.5-2°C warmer world, the challenging target of the Paris Agreement (http://unfccc.int/paris_agreement/items/9485.php), by looking at the paleorecord? Will a 1.5-2°C warmer world be a safe harbor and provide sustainable climate conditions for future societies? Will it avoid long-term tipping points that might have been crossed for a less-controlled future anthropogenic warming scenario?
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Figure 1: Skiing in a warmer world - Former PAGES co-chair, and Warmer Worlds Integrative Activity leader, Hubertus Fischer gets trapped by a sudden lack of snow in the Bernese Alps after the workshop. Although paleo evidence on skiing is severely limited, documentations of snowline changes exist. |
These questions are at the very heart of PAGES. Accordingly, PAGES recently initiated an integrative activity on “Warmer Worlds” with the goal to bring together the expertise in PAGES working groups and the entire community, and to distill the relevant information on these questions. The Warmer Worlds integrative activity members met for their first workshop, jointly co-sponsored by PAGES and the Oeschger Centre for Climate Change Research of the University of Bern. The expertise of the 50 international scientists in the room covered the whole range of paleoscience, including a large spectrum of paleoarchives and climate models to reconstruct changes in the Earth system. Time scales covered ranged from warmer periods in the more recent Holocene (Wanner et al. 2008; PAGES 2k consortium 2013), past warmer interglacials in the Quaternary (Past Interglacials Working Group of 2016) and all the way back to the Mid Pliocene Warm Period (Haywood et al. 2016), the time period where CO2 concentrations similar to the ones expected for a 2°C warmer world were encountered for the last time (Martinez-Boti et al. 2015).
The state of our paleo knowledge on different aspects of Earth system changes in a warmer world was summarized during plenary talks and three parallel sessions. This included (i) latest results on past changes in biogeochemical cycles with a focus on potential rapid greenhouse gas releases during warmer periods and feedbacks involved during these transitions, (ii) ice sheet and sea-level changes illustrating equilibrium sea-level increases of more than 6 m in a 2°C warmer world (Dutton et al. 2015), (iii) sea-ice and ocean circulation changes in response to warmer boundary conditions, (iv) the response of vegetation and ecosystems, (v) the risk of fire, storm and flood events in warmer worlds, and (vi) the change in climate variability accompanying generally warmer climate conditions.
Furthermore, the workshop facilitated a unique community writing effort to create an authoritative assessment of paleo evidence that will inform us on different aspects of a warmer future. Five chapters for a review paper have been prepared in parallel using web-based editing tools by five sub-groups of participants. These chapters are currently being collated by the authors of this report into a coherent paper, addressing the following overarching topics:
• Can past climate states provide suitable analogues for future warming and its impacts?
• Impacts and feedbacks connected to past warmer climate.
• Changes in climate variability and extreme events.
• Rates of change and tipping points.
• Constraining climate sensitivity from past warm periods.
This paper is scheduled to be submitted later this year and will serve as the base for the paleoscience contribution to a special IPCC report (http://www.ipcc.ch/report/sr15/) currently in preparation.
affiliationS
1Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Switzerland
2College of Earth, Ocean, & Atmospheric Sciences, Oregon State University, Corvallis, USA
3Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, University of New South Wales Sydney, Australia
contact
Hubertus Fischer: hubertus.fischerclimate.unibe.ch
references
Dutton A et al. (2015) Science 349: aaa4019
Haywood AM et al. (2016) Nat Commun 7: 10646
IPCC (2013) Climate change 2013 - the physical science basis, Cambridge University Press, 996pp
Martinez-Boti MA et al. (2015) Nature 518: 49-54
PAGES 2k consortium (2013) Nat Geo 6: 339-346
Past Interglacials Working Group of PAGES (2016) Rev Geophys 54: 162-219