ALBERT

Description: Networks of eddy-covariance (EC) towers such as AmeriFlux, ICOS and NEON are vital for providing the necessary distributed observations to address grand challenges in earth system and carbon cycle science. NEON, once fully operational with 47 tower sites, will represent the largest single-provider EC network globally. Its standardized observation and data processing suite is designed specifically for inter-site comparability and analysis of continental-scale ecological change, including rich contextual data such as airborne remote sensing and in-situ sampling bouts. First carbon cycle products become available in 2017, including data and software. These products strive to incorporate lessons-learned through collaborations with AmeriFlux, ICOS, LTER and others, to suggest novel systemic solutions, and to synergize ongoing research efforts across science communities. Here, we present an overview of the ongoing product release, alongside efforts to integrate and synergize with existing infrastructures, networks and communities. Near-real-time carbon cycle observations in “basic” and “expanded”, self-describing HDF5 formats become accessible from the NEON Data Portal, including an Application Program Interface. A pilot project is underway to investigate their subsequent ingest into the AmeriFlux processing pipeline, together with inclusion in FLUXNET globally harmonized data releases. Software for reproducible, extensible and portable data analysis and science operations management also becomes available. This includes the eddy4R family of R-packages underlying the carbon cycle data product generation, together with the ability to directly participate in open development via GitHub version control and Dockerhub image hosting. In addition, templates for science operations management include a web-based field maintenance application and a graphical user interface to simplify problem tracking and resolution along the entire data chain. We hope that this first release of NEON carbon cycle products can initiate further collaboration and synergies in challenge areas, and would appreciate input and discussion on continued development.

Description: The goal of this study is to scale aircraft measured fluxes of sensible and latent heat to the North Slope of Alaska and develop high resolution flux maps. For this purpose we analyzed an eddy-covariance data set obtained by the research aircraft POLAR 5 as part of the AIRMETH-2012 campaign, and investigated the spatial patterning of energy fluxes. Environmental response functions between flux observations and corresponding biophysical and meteorological drivers were estimated using a combination of time-frequency decomposition, dispersion modeling and machine learning. The extracted relationships are then used to scale observational data across heterogeneous Arctic landscapes, thus improving the spatial coverage and representativeness of the energy fluxes. Maps of projected energy fluxes are used to asses energy partitioning in northern ecosystems and to determine dominant energy exchange processes of permafrost area.

Description: Arctic wetlands associated with permafrost as well as thawing permafrost emit the greenhouse gas methane (CH4). Two important contributors are recent microbial activity in the active layer or taliks (biogenic CH4), and deeper fossil sources where pathways through the permafrost exist (geologic CH4). Current emission estimates vary strongly between different models. Moreover, there is still disagreement between bottom-up estimates from local field studies, and topdown estimates from atmospheric measurements. Here, we quantify permafrost CH4 emissions directly on the regional scale, based on the Airborne Measurements of Methane Fluxes Campaigns (AIRMETH) in the Mackenzie River Delta region, Canada, in July 2012 and 2013 [Kohnert et al., 2014]. The Mackenzie Delta is the second largest Arctic delta (13,000 km2). Our measurements covered an area extending 320 km from west to east (140°58’W to 133°22’W) and of 240 km from north to south (69°33’N to 67°26’N). The study area comprises the delta itself, the adjacent Yukon coastal plain, and Richards Island north east of the delta. The area surrounding the delta is described as continuous permafrost zone where the permafrost reaches a thickness of 300 m along the coastal plain and 500 m on Richards Island. In the delta itself the discontinuous permafrost reaches a maximum thickness of 100 m. The northern part of the study area is crossed by geological faults and underlain by oil and natural gas deposits. We analyse the regional pattern of CH4 fluxes and estimate the contribution of geologic emissions to the total CH4 budget of the delta. CH4 fluxes were calculated with a time-frequency resolved version of the eddy-covariance technique [Metzger et al., 2013], followed by the calculation of flux topographies [Mauder et al., 2008]. The result is a 100 m resolved gridded flux map within the footprints of the flight tracks. The results provide the first regional estimate of CH4 release from the Mackenzie Delta and the adjacent coastal plain. We distinguish geological gas seeps from biogenic sources by their strength, and show that geologic sources contribute strongly to the annual CH4 budget of the study area: One percent of the covered area contains the strongest geological seeps which contribute disproportionately to an annual emission estimate. The contribution of geological sources to CH4 emission warrants further attention, in particular in areas where permafrost is vulnerable to increased geologic gas migration due to thawing and opening of new pathways. The presented map can be used as a baseline for future CH4 flux studies in the Mackenzie Delta. References Kohnert, K.; Serafimovich, A.; Hartmann, J. and Sachs, T. [2014]: Airborne measurements of methane fluxes in alaskan and canadian tundra with the research aircraft “polar 5”. In Reports on Polar and Marine Research, volume 673. Alfred Wegener Institue Bremerhaven, pp. 81. Mauder, M.; Desjardins, R.L. and MacPherson, I. [2008]: Creating surface flux maps from airborne measurements: Application to the Mackenzie area GEWEX study MAGS 1999. Boundary-Layer Meteorology, 129:431–450, 2008. Metzger, S.; Junkermann, W.; Mauder, M.; Butterbach-Bahl, K.; Trancón y Widemann, B.; Neidl, F.; Schäfer, K.; Wieneke, S.; Zheng, X. H.; Schmid, H. P. and Foken, T. [2013]: Spatially explicit regionalization of airborne flux measurements using environmental response functions. Biogeosciences, 10(4):2193–2217, 2013. doi:10.5194/bg-10-2193-2013.

Description: Large uncertainties still exist in the global methane budget with clear disagreements between bottom-up and top-down estimates, limiting confidence in climate projections. This is particularly true in the Arctic, which is warming rapidly while storing vast amounts of organic carbon that could potentially be released as carbon dioxide and methane, adding a new greenhouse gas source of unknown magnitude. Regional scale methane emission estimates and functional relationships between potential drivers and methane fluxes are currently unavailable. The Airborne Measurements of Methane Fluxes (AIRMETH) campaigns are designed to quantitatively and spatially explicitly address this question. While ground-based eddy covariance (EC) measurements provide continuous in-situ observations of the surface-atmosphere exchange of energy and matter, they are rare in the Arctic permafrost zone and site selection is bound by logistical constraints among others. Consequently, these observations cover only small areas that are not necessarily representative of the region of interest. Airborne measurements can overcome this limitation by covering distances of hundreds of kilometers over time periods of a few hours. During the AIRMETH-2012 campaign aboard the research aircraft POLAR 5 we measured turbulent exchange fluxes of energy and methane along thousands of kilometers covering the North Slope of Alaska. Time-frequency (wavelet) analysis, footprint modeling, and machine learning techniques are used to extract spatially resolved turbulence statistics and fluxes, spatially resolved contributions of land cover and biophysical surface properties to each flux observation, as well as regionally valid functional relationships between environmental drivers and observed fluxes that can explain spatial flux patterns and – if available in temporal resolution – allow for spatio-temporal scaling of the observations. Here we present a 100 m resolution gridded methane flux map for the North Slope of Alaska, covering about 90.000 km2. We show that surface properties like elevation, temperature, and NDVI along with meteorological drivers such as shortwave radiation, water vapor mixing ratio, and horizontal wind speed are sufficient to explain and project the measured fluxes. The median methane flux for the campaign period (end of June/beginning of July) was 19.4 mg m−2 d−1 after excluding all values with � 30 % standard error. The largest fluxes were observed along the coast and in the Arctic coastal plain, decreasing towards the Brooks Range.

Description: Among other regions of the world, the Arctic is strongly affected by climate change. Globally, it is the region with the most pronounced warming, leading to permafrost warming and thawing. Part of the 1,300 Pg soil organic carbon currently stored in the frozen ground is already and might be further released as carbon dioxide (CO2) and methane (CH4). CO2 is released through aerobic soil respiration and from plant roots, but also sequestered through photosynthesis. CH4 emission can be attributed to either recent microbial activity or to past microbial or thermal decomposition and is spatially heterogeneous. To our knowledge, regional assessments of the total carbon flux (CO2 and CH4) based on high frequency airborne measurements do not exist. Here we determine the regional pattern of CO2 and total carbon emissions (CO2 + CH4) of the Mackenzie Delta region, Canada, based on the Airborne Measurements of Methane Fluxes Campaign (AIRMETH) in July 2013 [Kohnert et al., 2014]. The Mackenzie Delta is the second largest arctic delta (13,000 km2). Our measurements covered an area extending 320 km from west to east (140°58’ W to 133°22’W) and of 240 km from north to south (69°33’N to 67°26’N). The study area is heterogeneous and comprises the delta itself, the adjacent Yukon coastal plain, and Richards Island north east of the delta. Part of the delta is located north of the treeline. The area surrounding the delta is described as continuous permafrost zone where the permafrost reaches a thickness of 300 m along the coastal plain and 500 m on Richards Island. In the delta itself the discontinuous permafrost reaches a maximum thickness of 100 m. For the AIRMETH campaign we used the research aircraft Polar 5. Equipped with a 5-hole probe, the usual meteorological sensors, and a fast greenhouse gas analyser (GGA 24EP, Los Gatos Research Inc.) we flew at 30 - 60 m above ground at a true airspeed of 60 m s−1. CO2 and CH4 fluxes were calculated with a timefrequency resolved version of the eddy-covariance technique [Metzger et al., 2013]. We calculated flux topographies [Mauder et al., 2008] to resolve the fluxes along a linear flight track to the area within the footprint of the measurements. The result is a 100 m resolved gridded carbon flux map within the footprints of the flight tracks. Based on the flux topographies we produce a map of the regional pattern of peak growing season carbon fluxes. References Kohnert, K.; Serafimovich, A.; Hartmann, J. and Sachs, T. [2014]: Airborne measurements of methane fluxes in alaskan and canadian tundra with the research aircraft “polar 5”. In Reports on Polar and Marine Research, volume 673. Alfred Wegener Institue Bremerhaven, pp. 81. Mauder, M.; Desjardins, R.L. and MacPherson, I. [2008]: Creating surface flux maps from airborne measurements: Application to the Mackenzie area GEWEX study MAGS 1999. Boundary-Layer Meteorology, 129:431–450, 2008. Metzger, S.; Junkermann, W.; Mauder, M.; Butterbach-Bahl, K.; Trancón y Widemann, B.; Neidl, F.; Schäfer, K.; Wieneke, S.; Zheng, X. H.; Schmid, H. P. and Foken, T. [2013]: Spatially explicit regionalization of airborne flux measurements using environmental response functions. Biogeosciences, 10(4):2193–2217, 2013. doi:10.5194/bg-10-2193-2013.

Description: Arctic ecosystems are undergoing a very rapid change due to global warming and their response to climate change has important implications for the global energy budget. Therefore, it is crucial to understand how energy fluxes in the Arctic will respond to any changes in climate related parameters. Attribution of these responses, however, is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. Ground-based measurements of surface fluxes provide continuous in-situ observations of the surfaceatmosphere exchange. But these observations may be non-representative because of spatial and temporal heterogeneity, indicating that local observations cannot easily be extrapolated to represent global scales. Airborne eddy covariance measurements across large areas can reduce uncertainty and improve spatial coverage and spatial representativeness of flux estimates. Here, we present the potential of environmental response functions for quantitatively linking energy flux observations over high latitude permafrost wetlands to environmental drivers in the flux footprints. We used the research aircraft Polar 5 equipped with a turbulence probe as well as fast temperature and humidity sensors to measure turbulent energy fluxes across the Alaskan North Slope. We used wavelet transforms of the original highfrequency data, which enable much improved spatial discretization of the flux observations, and determine biophysically relevant land cover properties in the flux footprint. A boosted regression trees technique is then employed to extract and quantify the functional relationships between energy fluxes and environmental drivers. Using the extracted environmental response functions and meteorological fields simulated by the Weather Research and Forecasting (WRF) model, the surface energy fluxes were then projected beyond the measurement footprints across the entire North Slope of Alaska.

Description: Networks of eddy-covariance (EC) towers such as AmeriFlux, ICOS and NEON are vital for providing the necessary distributed observations to address interactions at the soil-vegetation-atmosphere interface. NEON, close to full operation with 47 tower sites, will represent the largest single-provider EC network globally. Its standardized observation and data processing suite is designed specifically for inter-site comparability and analysis of feedbacks across multiple spatial and temporal scales. Furthermore, NEON coordinates EC with rich contextual observations such as airborne remote sensing and in-situ sampling bouts. In January 2018 NEON enters its operational phase, and EC data products, software and services become fully available to the science community at large. These resources strive to incorporate lessons-learned through collaborations with AmeriFlux, ICOS, LTER and others, to suggest novel systemic solutions, and to synergize ongoing research efforts across science communities. Here, we present an overview of the ongoing product release, alongside efforts to integrate and collaborate with existing infrastructures, networks and communities. Near-real-time heat, water and carbon cycle observations in “basic” and “expanded”, self-describing HDF5 formats become accessible from the NEON Data Portal, including an Application Program Interface. Subsequently, they are ingested into the AmeriFlux processing pipeline, together with inclusion in FLUXNET globally harmonized data releases. Software for reproducible, extensible and portable data analysis and science operations management also becomes available. This includes the eddy4R family of R-packages underlying the data product generation, together with the ability to directly participate in open development via GitHub version control and DockerHub image hosting. In addition, templates for science operations management include a web-based field maintenance application and a graphical user interface to simplify problem tracking and resolution along the entire data chain. We hope that this presentation can initiate further collaboration and synergies in challenge areas, and would appreciate input and discussion on continued development. Plain Language Summary For a sustained period of time the eddy-covariance and boundary layer communities have invested technical and scientific expertise into the construction of the National Ecological Observatory Network (NEON). In January 2018 NEON enters its operational phase, and the time has come for our communities to reap the first fruits of their efforts! This presentation intends to create awareness of the resources that become available to our communities: interoperable flux data products, software and assignable asset services. We focus on how these resources will permit to elucidate interactions at the soil-vegetation-atmosphere interface for decades to come: continuous eddy-covariance observations of the surface-atmosphere exchange are tightly coordinated with rich contextual data such as airborne remote sensing and in-situ sampling bouts. In this way new investigative dimensions are provided to capture land-atmosphere feedbacks across multiple spatial and temporal scales.