Prof. Per Ambus
Geosciences and Natural Resource Management, Copenhagen University. Personal website
"Greenhouse gas fluxes from Arctic tundra in a changing climate"
Greenhouse gas (GHG) fluxes from Arctic have attained increasing interest. This as a consequence of global climatic changes anticipated to increase soil temperature and thawing permafrost in vast regions, with significant implications for land-atmosphere GHG exchange. This lecture outlines characteristics of Arctic GHG fluxes with a main focus on the powerful non-CO2 gas species methane (CH4) and nitrous oxide (N2O). The dominant processes and their anticipated interactions with climatic conditions are outlined, and perspectives for future GHG fluxes in a changing Arctic discussed. Northern latitudes contribute in the range 4-5% to global CH4, whereas the contribution to N2O remains unresolved. Meanwhile, research has demonstrated that global warming and permafrost thaw may significantly increase emission rates of these two powerful GHGs. The presentation will also include results from recent and ongoing research in Disko, Western Greenland. This work includes several seasons of in situ measurement of GHG fluxes in large-scale climate manipulation experiments with snow fences, to manipulate winter-time snow cover, combined with open-top chambers to increase temperature.
Prof. Dietrich Borchardt
Aquatic Ecosystems Analysis and Management, UFZ Leipzig, Technical University of Dresden. Personal website
"Trends and events in hydrosystems: a new multi-scale and cross-compartment observation approach deciphering controls and impacts of hydrological extremes"
We have to consider that climate change may lead to an increase in global average temperature of at least 2°C in the near future. There is substantial evidence that this climate change will be associated with an increase in the frequency, intensity or a shift in timing of extreme events such as rainfall extremes and dryness, elevated flooding and extended low water periods, all with as yet unforeseeable environmental and socioeconomic consequences and feedbacks. Such meteorological and hydrological events are restricted in time and spatially distinct, but their ultimate impact may be significant for much larger regions (e. g. downstream catchment areas flooded from run-off generation in upstream headwaters) and with delayed effects (e.g. algal blooms in the vegetation periods in coastal zones triggered by legacy nutrient pulses from inland sources). The presentation will exemplarily analyze such event chains with emphasis on hydrological extremes and the processes they trigger: the mobilization of nutrients, carbon and harmful substances, their passage from land based sources into the aquatic environment and how these are transported or retained. We present a new modular and event driven observation concept that captures events from their origin to their fading and that complements existing data and models from long-term monitoring and observatories. This concept systematically combines mobile and high resolution event monitoring with stationary integrative observation and as such it aims at unraveling the (potentially decisive) role of the increasing frequency and intensity of extreme meteorological and hydrological events on the status of our tightly coupled hydrologic, ecological and socio-economic environment.
Dr. Fabrizio Fenecia
Eawag - Swiss Federal Institute of Aquatic Science and Technology, Dept. Systems Analysis. Personal website
"Modelling the meso-scale: informing model structure from data analysis"
The challenge of building a process based model in a small catchment can be alleviated by fieldwork experience. But when catchments start being too big for experimental hydrology, the model building process becomes even more challenging. Our goal is to build a distributed process based model for simulating streamflow within the Mosel basin (30.000 km2) at 26 nested subcatchments. We propose a 2-stages approach. In a first “data-analysis” stage, similar to catchment classification studies, we seek whether signatures of catchment function can be explained by signatures of climate variability or indicators of geophysical characteristics of the catchment. These relations are then used to inform a distributed “perceptual” model of catchment function. In a second “hypothesis-testing” stage, the model is subject to a phase of testing and further improvement. The first “data-analysis” stage outlines the importance of geology in controlling quickflow vs. baseflow partitioning, of topography in controlling the shape of the hydrograph, as well as of precipitation in controlling the overall water balance. These insights were used to inform model decisions such as how to break-up the landscape, which structure to assign to each landscape element, and how to distribute model parameters in space. The second “hypothesis-testing” stage was used to confirm the validity of model decisions, and test model alternatives. Overall, we show that large part of the variability in the observed streamflow at the 26 catchments can be well simulated by a parsimonious model, with a few spatially distributed parameters. Our approach is a step towards a more systematic distributed model development approach.
Prof. Martyn Futter
Swedish University of Agricultural Sciences. Personal website
"Beyond the mesoscale – new thinking about the role of time in water quality modelling"
Our conceptual model of the processes controlling water quality has been in large part driven by infrequent (biweekly or monthly) and relatively short term (less than a decade) observations, many of which have been collected by discrete sampling of river mouths. Furthermore, those of us in the water quality modelling community have adopted model structures that work well for hydrological simulations but are not consistent with either measurements or biogeochemical process conceptualization.
While simulations developed on the basis of mesoscale infrequent, relatively short term measurements and model structures designed for simulating flood discharge peaks are widely used for catchment management, there are increasing concerns about their fitness for purpose. Predictions based on obsolete process understanding and questionable model structures are likely to result in misleading conclusions and poor management decisions.
The process understanding incorporated in water quality models is being challenged at both ends of the temporal spectrum. On the one hand, high frequency and other in-situ measurements offer new awareness of short term temporal variability, while on the other hand, ever longer observational time series raise questions about stationarity and the “elusive baseline”. Here, I will discuss how observations from both ends of the temporal spectrum can improve our conceptualization of catchment biogeochemical processes, and how this new understanding can inform the structure of a new generation of water quality models.
Prof. Sarah Garré
Gembloux Agro-Bio Tech, Université de Liège, France. Personal website
"The ecotron as controlled surrogate for reality. Too good to be true?"
by Sarah Garré, Bernard Longdoz, Vincent Leemans
Finding solutions to adapt to the impact of global change is still one of the most important challenges of the 21st century. While huge modelling advances have been made and experimental methods to study the earth system are diversifying, a major problem to find those solutions remains: the unclosed gap between spatial and temporal scales. Results from controlled experiments in pots or greenhouses are sometimes difficult to relate to observations at the field and landscape scale due to the complex interplay of various processes. In addition, it has been hard to reproduce the future effects of climate change experimentally, leading to an inevitable extrapolation of model predictions to zones where no validation is possible.
Ecotrons provide unprecedented possibilities to study the soil-vegetation-microbiome-atmosphere continuum in highly controlled conditions and this under any climate scenario of interest. In this presentation, we will present the new Ecotron facility of the TERRA Research Center in Gembloux, Belgium designed to submit six mesocosms (small ecosystems) installed on lysimeters (2m² X 1,5m), to any climatic conditions desired and see how it can reproduce (or not) the current and future in-nature reality. In addition to the controlled variables, instrumentation is set up to monitor energy and water budget and ecosystem functions (yield and production quality, GHG mitigation and C storage, water retention capacity and leaching quality, soil fertility,…)
In the first experiment planned, we will compare the behavior of winter wheat plots submitted to present and future climatic conditions. The present conditions will mimic the situation already recorded on the Lonzee ICOS site. The future scenario will represent a typical year of the 2050-2070 period (drift of the mean annual value and increase of the temporal variabiity) and chosen for its ability to produce a contrasting crop yield.
The results will also give us information about the ability of ecotrons to reproduce a realistic ecosystem functionning and expose which aspects of plant growth and soil behavior are well and not well reproduced in the artificially generated climatic conditions. This phase is essential to demonstrate the actual potential and shortcomings of this cross-cutting research infrastructure.
Prof. Tiffany Knight
German Center for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig. Personal website
"Biodiversity change across space and time using historic data and distributed networks"
Global change factors, such as climate and land use change have the potential to alter the diversity and composition of our ecosystems, with important consequences for humanity. Understanding biodiversity change requires sampling communities in space and time using consistent methodology. First, this talk will focus on the value of historic datasets, by illustrating an example using Hermann Müller's data on 8000 interactions between plants and insect pollinators in the Alps from 1874-1879 and another example from UFZ TERENO plant biodiversity sampling. Second, this talk will discuss key findings from other projects that use distributed networks for observing biodiversity change. Third, this talk will present new results on plant-pollinator interactions in the UFZ TERENO site and discuss opportunities for expansion to other sites.
Director of Strategic Development, Environment and Infrastructure, Battelle-National Ecological Observatory Network (NSF-NEON), Boulder, US. Personal website
"Hard Knocks: Developing Environmental Observatories for long-term observations"
Environmental Observatories (EOs) are emerging globally out of necessity for large-scale integrated data and scope to address both important science questions and societal imperatives. Some develop organically from bottom-up networks, others more top-down, formal infrastructure. They are designed to complement other research projects, programs, networks, innovation, and policy—not in competition with. However, developing EOs are themselves a frontier activity. No two EO development paths are alike, and there are lessons to be learned from all. Balancing top-down approaches and rich bottom-up scientific creativity continues to be a challenge. This is a pragmatic keynote in; (i) the NEON Science design and development approach is discussed, (ii) challenges to deliver NEON ‘Observatory Science’, (iii) overall common near-death experiences among EOs, and (iv) ongoing cultural barriers to broker top-down and bottom-up approaches.
Dr. Lutz Merbold
Mazingira Centre, International Livestock Research Institute (ILRI), Nairobi, Kenya. Personal website
"The need to combine different methods to understand ecosystem greenhouse gas exchange: a grassland case study"
Quantifying greenhouse gas (GHG) exchange between ecosystems and the atmosphere is essential to identify potential sinks and source and furthermore to evaluate potential changes in GHG fluxes caused by climate change and/or land use change. Besides a variety of existing methods that are capable of deriving GHG measurements from ecosystems in-situ, biogeochemical process models are particularly powerful to simulate deviations in GHG exchange in the future. Thereby the models could go as far as testing specific interventions to mitigate GHG emissions a priori. Neither individual measurement approaches nor models should be used independently as each method focuses on an individual scale or process and only the combination of as many approaches as possible will allow to understand an ecosystem and particularly ecosystem GHG exchange comprehensively. Here we give an example from a Central European grassland where soil greenhouse gas measurement, eddy covariance GHG flux measurement, isotopic measurements as well as several biogeochemical process models were used successfully in order to quantify GHG exchange in a first stage and reduce the GHG emissions in a second stage. The study not only evaluated the GHG exchange between the grassland system and the atmosphere but further included a full assessment of the productivity of the system in order to derive GHG emission intensities.
Dr. Stefan Metzger
National Ecological Observatory Network (NSF-NEON), Boulder, US. Personal website
"Mapping evapotranspiration from flux tower and aircraft measurements – how so?"
by Metzger, S., Desai, A. R., Durden, D., Florian, C., Hartmann, J., Kohnert, K., Luo, H., Pingintha-Durden, N., Sachs, T., Serafimovich, A., and Xu, K.
Understanding evapotranspiration through space and time requires the joint use of observations across various scales, and from disparate measurement platforms. Present-day examples include large-scale satellite remote sensing missions to monitor the earth system such as the forthcoming NASA ECOSTRESS. These in turn rely on distributed in-situ observations for calibration and validation, such as from eddy-covariance flux tower networks the likes of AmeriFlux, ICOS, NEON and TERENO, or intensive flux aircraft campaigns. However, oftentimes the different types of observations overlap only fractionally in space and time at best, posing a substantial and frequently ignored challenge for their joint use.
Here, the Environmental Response Function (ERF) integrative data processing can come to the rescue. This is achieved by approximating an information continuum through catalyzing the strengths of process and artificial intelligence concepts: ERF complements existing mathematical descriptions of better-understood processes such as atmospheric dispersion with observations from towers, aircraft, and satellites about less well-understood phenomena. It then mines the joint information content and yields the most complete solution that is possible from the processes and observations provided.
Here, we investigate evapotranspiration maps at high spatial (10 – 100 m) and temporal (0.5 h) resolutions as one such solution: ERF can map extensive areas around individual flux towers (order 1 – 10 km2) and flux aircraft missions (order 1000 km2) with spatial coverage in excess of 80%. Equipped with this information hot spots and hot moments can be clearly located, ecohydrological and ecophysiological processes can now be analyzed in space and time, and traditional scale gaps can be bridged. This opens the door not only for greatly improved calibration, validation and data assimilation, but ultimately for harnessing the full complement of available information for modeling at the Earth system scale.
Dr. habil. Laurent Pfister
Luxembourg Institute of Science and Technology. Personal website
"Catchment storage estimation, dynamics and controls – Insights gained from a long-term monitoring programme in the nested catchment set-up of the Alzette River basin (Luxembourg)"
While bedrock controls on catchment mixing, storage, and release functions have been increasingly investigated in recent years, comparative analyses across different neighboring lithologies remains a major challenge. In the Alzette River basin (Luxembourg) we have examined 9 years’ worth of precipitation and discharge data (across 16 nested catchments), and 6 years of fortnightly stable isotope data in streamflow (for a subset of 12 catchments), to investigate catchment physiographic controls on:
- Streamflow – we studied the relationship between catchment bedrock geology and streamflow regime metrics (i.e. winter and annual runoff/precipitation ratios and average summer/winter discharge ratios);
- Storage – relying on catchment storage as a metric for catchment comparison, we derived catchment storage deficits from water balance calculations and quantified how storage and storage-discharge relationships differ between catchments and scales;
- Isotope response and catchment mean transit time (MTT) – we investigated how the standard deviation in streamflow dD and ratios of d18O amplitudes in streamflow and precipitation (AS/AP), as proxies for catchment averaged damping of isotopic signatures, and catchment MTT, relate to bedrock geology, storage and catchment area.
Prof. Scott St. George
Dept. of Geography, Environment and Society, University of Minnesota, USA. Personal website
"Disentangling the decadal ‘knot’ in high-resolution paleoclimatology"
Even after more than a century of coordinated monitoring, instrumental weather observations are still too short to adequately constrain decadal or multidecadal behavior in the Earth’s climate system. Leading climatologists and climate modelers have called for the wider application of high-resolution proxy records to decadal variability and prediction studies, and our community has responded by producing new paleoclimate products that specifically target this type of ‘intermediate-term’ behavior. But we now also know our medium changes that message: the biological and geological systems that encode climate information into natural archives often also alter the original ‘input’, usually due to either seasonal filtering or non-climatic persistence. In this talk, we’ll discuss some of the challenges inherent to the use of high-resolution proxies to study decadal or multi-decadal climate variability, and suggest strategies that might clarify how climate acts on those timescales. And we’ll also present a new theoretical framework that could help paleo-scientists evaluate competing ideas about the causes of decadal- or multi-decadal events known to have occurred during the past one or two millennia.
Prof. Dr. Susan Steele-Dunne
Civil Engineering and Geosciences, TU Delft. Personal website
"Recent advances in the development of radar as a tool for monitoring vegetation water dynamics"
Spaceborne SAR and scatterometer systems deliver radar backscatter data at a range of spatial resolutions from meters to tens of kilometers. Radar backscatter is sensitive to soil moisture, and vegetation water content as well as surface and vegetation geometry. Spaceborne radar data have been used operationally for soil moisture retrieval, land cover classification and above ground biomass monitoring. An implicit assumption in each of these applications is that the vegetation constitutes a relatively static dielectric medium.
In reality, vegetation is highly dynamic. Vegetation acts as an interface between the earth's surface and the atmosphere, modulating exchanges of water, carbon and energy and responding to environmental stressors. Potential gradients between the root zone and atmosphere drive moisture transport within the vegetation, influencing both the total amount of water in the vegetation and its internal distribution at sub-daily scales. Results from a recent field experiment, centered on a new L-, C- and X-band radar system, will be used to illustrate how these dynamics affect radar backscatter as a function of frequency, polarization and viewing geometry during a growing season. Spaceborne SAR and scatterometer data will be used to demonstrate that phenomena observed at field scale are also observed at footprint scale, yielding new opportunities to observe vegetation water dynamics in agricultural and natural ecosystems.
Prof. Markus Weiler
Institute of Hydrology, Freiburg University. Personal website
"Combining experiments, monitoring and modelling to understand and predict nutrient fluxes in temperate ecosystems"
Phosphorus (P) is an essential element for primary productivity of an ecosystem. Natural forests are known to be limited in P supply and therefore develop tight P-recycling strategies. The P availability is, however, significantly affected by P-losses due to hydrological fluxes in the surface and subsurface during rainfall or snowmelt events. Since typical observations of runoff and nutrient losses sample baseflow conditions and average rainfall-runoff events, possible tipping points for extreme events are generally not known. However, climate change may increase the probability of such extreme events and the loss of essential nutrients like phosphorous may disproportionally increase.
Prof. Marek Zreda
Hydrology and Water Resources, University of Arizona. Personal website
"Cosmic-ray hydrology: principles and detectors"
Cosmogenic neutrons can be used to measure soil water content in the root zone of soil for applications in field and catchment-scale hydrology, land surface modelling, and agricultural water management. The method takes advantage of the strong sensitivity of neutrons with energies greater than 1 eV to hydrogen present in and above soil. Hydrogen removes those neutrons from the environment in the process called moderation resulting in their reduced density in air above the soil surface. The resulting inverse correlation between the neutron density in air and the hydrogen density in soil is used to convert measured neutron intensity to soil water content. Accounting for hydrogen sources other than soil water is necessary for accurate computation of soil water content.
Neutrons are measured with the instrument called cosmogenic neutron sensor or probe. The probe’s sensing element consists of a thermal neutron detector surrounded by a moderator. The probe’s horizontal footprint is measured in hectometers and the vertical footprint in decimeters. Both depend on soil water content and other hydrogen present in and above soil. The probe can be installed permanently (stationary probe), giving time series of neutron intensity and soil water content, or moving (rover), used for mapping of neutrons and soil water content along lines or over areas. Networks of stationary probes exist, the largest being in Germany (TERENO), Australia (CosmOz), the UK (COSMOS-UK) and the USA (COSMOS). The aim is to analyze data from all locations within the network together and link the results to large-scale hydrological, meteorological, land-surface and atmospheric models. That is yet to happen.
Recent work showed that the horizontal footprint is more complex than hitherto thought: the probe has very high sensitivity to meter-sized heterogeneities. That finding led to the development of two new instruments. One reduces the sensitivity to local neutrons and improves wide-area sensing of soil moisture. The other instrument increases the sensitivity to local neutrons, reduces the contribution by far-away neutrons and becomes a small-footprint sensor for high-resolution mapping of soil moisture.