Benjamin Runkle

Spatial and seasonal variability of polygonal tundra water balance: Lena River Delta, northern Siberia (Russia)

The summer water balance of a typical Siberian polygonal tundra catchment is investigated in order to identify the spatial and temporal dynamics of its main hydrological processes. The results show that, besides precipitation and evapotranspiration, lateral flow considerably influences the site-specific hydrological conditions. The prominent microtopography of the polygonal tundra strongly controls lateral flow and storage behaviour of the investigated catchment. Intact rims of low-centred polygons build hydrological barriers, which release storage water later in summer than polygons with degraded rims and troughs above degraded ice wedges. The barrier function of rims is strongly controlled by soil thaw, which opens new subsurface flow paths and increases subsurface hydrological connectivity. Therefore, soil thaw dynamics determine the magnitude and timing of subsurface outflow and the redistribution of storage within the catchment. Hydraulic conductivities in the elevated polygonal rims sharply decrease with the transition from organic to mineral layers. This interface causes a rapid shallow subsurface drainage of rainwater towards the depressed polygon centres and troughs. The re-release of storage water from the centres through deeper and less conductive layers helps maintain a high water table in the surface drainage network of troughs throughout the summer.RésuméLe bilan d’eau estival d’un bassin d’alimentation typique de la toundra polygonale sibérienne a fait l’objet d’investigations afin d’identifier la dynamique spatio-temporelle des ses principaux processus hydrologiques. Les résultats montrent que, à côté de la précipitation et de l’évapotranspiration, un flux latéral influence considérablement les conditions hydrogéologiques spécifiques du site. La microtopographie marquée de la toundra polygonale contrôle fortement l’écoulement latéral et la modalité d’emmagasinement du bassin objet de l’investigation. Les bords intacts des polygones centrés bas constituent des barrières hydrologiques, qui libèrent l’eau accumulée en été plus tard que les polygones à bords dégradés et dépressions au dessus des biseaux glacées dégradées. La fonction barrière des bordures est fortement contrôlée par le dégel du sol, qui ouvre de nouveaux chenaux d’écoulement en subsurface et en accroît la connectivité hydrologique. C’est pourquoi, la dynamique du dégel détermine l’instant et le volume d’émission d’eau en subsurface et la redistribution de la réserve dans le bassin versant. Les conductivités hydrauliques des bordures polygonales élevées diminuent brusquement avec la transition d’horizons organiques à des horizons minéraux. Ceci cause un drainage superficiel rapide de l’eau de précipitation vers les centres déprimés des polygones et goulottes. Le relargage de l’eau en réserve depuis les centres à travers des couches plus profondes et moins conductrices aide à maintenir élevée la surface libre de l’aquifère sous le réseau de drainage superficiel des goulottes durant tout l’été.ResumenSe investiga el balance de agua de verano en una típica cuenca siberiana de polígonos de tundra para identificar la dinámica espacial y temporal de sus principales procesos hidrológicos. Los resultados muestran que, además de la precipitación y evapotranspiración, el flujo lateral influye considerablemente las condiciones hidrológicas del sitio específico. La destacada microtopografía de los polígonos de tundra controla fuertemente el comportamiento del flujo lateral y almacenamiento de la cuenca investigada. Los bordes intactos de los polígonos bajos centrados constituyen barreras hidrológicas, que liberan el agua de almacenamiento del verano después que los polígonos con bordes degradados y canales por encima de cuñas degradadas del hielo. La función de barrera de los bordes está controlada fuertemente por el deshielo del suelo, que abre nuevas trayectorias al flujo subsuperficial y aumenta la conectividad hidrológica subsuperficial. Además, la dinámica de deshielo del suelo determina la magnitud y el tiempo de la salida subsuperficial y la redistribución del almacenamiento dentro de la cuenca. Las conductividades hidráulicas en los bordes elevados del polígono disminuyen drásticamente con la transición de capas orgánicas a minerales. Esto causa un rápido drenaje subsuperficial somero del agua de lluvia hacia el centro de los polígonos deprimidos y canales. La reliberación del agua del almacenamiento desde el centro a través de capas menos conductivas y más profundas ayuda a mantener un nivel freático alto en la red de drenaje superficial de canales durante todo el verano.摘要为确定它的主要水文过程的时空动态,本文研究了一个典型的西伯利亚多边形冻原流域在夏季的水均衡。结果显示,除了降水和蒸发蒸腾,侧向流在相当程度上影响着特定场地的水文条件。多边形冻原主要的微地形特征强烈控制着研究流域的侧向流和储存行为。在中心偏低的多边形的完整边缘上建造水文屏障,以此可利用退化冰楔之上退化的边缘和凹槽在夏天释放储存的水。边缘上屏障的作用受到土壤解冻强烈的控制,解冻作用打开了地下水流的流径,提高了地下的水文连通性。因此,土壤解冻的动态决定了流出的地下水的规模和时间,以及流域内所储存水量的重新分配。升高的多边形边缘从有机层过渡到矿物层,渗透系数急剧减小。这造成了浅部雨水向凹陷的多边形中心和洼地迅速排水。所储存的水通过更深部的低渗透岩层从中心重新释放,这有助于夏季在地表凹槽排水系统中保持一个较高的水位。ResumoÉ investigado o balanço hídrico estival de uma típica bacia hidrográfica de tundra poligonal para identificar as dinâmicas espaciais e temporais dos seus principais processos hidrológicos. Os resultados mostram que, para além da precipitação e da evapotranspiração, o escoamento lateral influencia consideravelmente as condições hidrológicas em cada local. A característica microtopografia da tundra poligonal controla fortemente o escoamento lateral e o comportamento do armazenamento na bacia investigada. Os bordos intactos dos polígonos com centro deprimido constituem barreiras hidrológicas que libertam a água armazenada mais tarde no verão do que nos polígonos com bordos degradados e fendas situadas acima das cunhas de gelo degradadas. A função de barreira dos bordos é fortemente controlada pelo descongelamento do solo que abre novos percursos de escoamento subterrâneo e incrementa a conectividade hidrológica subsuperficial. Consequentemente, a dinâmica do descongelamento do solo determina a magnitude e a temporização do escoamento e a redistribuição do armazenamento dentro da bacia. A condutividade hidráulica nos bordos poligonais elevados diminui drasticamente com a transição entre as camadas orgânicas a as camadas minerais. Isto provoca uma rápida drenagem subsuperficial pouco profunda da água de chuva em direção aos centros deprimidos e às fendas. A re-libertação da água armazenada a partir dos centros através de camadas mais profundas e menos condutivas ajudam a manter ao longo do verão um nível de água elevado na rede de drenagem superficial formada pelas fendas.

Seasonal variability as a source of uncertainty in the West Siberian regional CH4 flux upscaling

This study compares seasonal and spatial variations in methane fluxes as sources of uncertainty in regional CH4 flux upscaling from the wetlands of West Siberia. The study examined variability in summertime CH4 emissions from boreal peatlands, with a focus on two subtaiga fen sites in the southern part of West Siberia (Novosibirskaya oblast). We measured CH4 flux, water table depth, air and peat temperature, pH and electric conductivity of peat water during three field campaigns in summer 2011 (9‐12 July, 26‐28 July and 20‐21 August). Fluxes were measured with static chambers at sites chosen to represent two of the most widespread types of wetlands for this climatic zone: soligenous poor fens and topogenous fens. In both sites the water table level acts as the primary control on fluxes. For the poor fen site with good drainage, water table controls CH4 fluxes on the seasonal scale but not on a local spatial scale; for the fen site with weak drainage and microtopographic relief, the water table controls fluxes on the local spatial scale, but does not drive seasonal variations in the flux magnitude. This difference in hydrology shows the necessity of including detailed wetland type classification schemes into large-scale modeling efforts. From these three measurement periods, we estimated the relative seasonal variation in CH4 emissions as 8% for the fen site and 26% for the poor fen site. These results were compared to estimates of other sources of uncertainty (such as interannual variation and spatial heterogeneity) to show that quantifying seasonal variability is less critical than these other variations for an improved estimate of regional CH4 fluxes. This research demonstrates and ranks the challenges in upscaling measured wetland CH4 fluxes across West Siberia and can guide future field campaigns.

Attenuation Correction Procedures for Water Vapour Fluxes from Closed-Path Eddy-Covariance Systems

Evapotranspiration is a source of water vapour to the atmosphere, and as a crucial indicator of landscape behaviour its accurate measurement has widespread implications. Here we investigate errors that are prevalent and systematic in the closed-path eddy-covariance measurement of latent heat flux: the attenuation of fluxes through dampened cospectral power at high frequencies. This process is especially pronounced during periods of high relative humidity through the adsorption and desorption of water vapour along the tube walls. These effects are additionally amplified during lower air temperature conditions. Here, we quantify the underestimation of evapotranspiration by a closed-path system by comparing its flux estimate to simultaneous and adjacent measurements from an open-path sensor. We apply models relating flux loss to relative humidity itself, to the lag time of the cross-correlation peak between the water vapour and vertical wind velocity signals, and to models of cospectral attenuation relative to the cospectral power of simultaneous sensible heat-flux measurements. We find that including the role of temperature in modifying the attenuation–humidity relationship is essential for unbiased flux correction, and that physically based cospectral attenuation methods are effective characterizers of closed-path instrument signal loss relative to the unattenuated flux value.

One Metaphor—Several Meanings: An Interdisciplinary Approach to Sustainable Development

This paper presents reflections on how sustainable development (SD) is defined as a research topic and on differences in references to SD in research. The paper argues that the reference of SD as a research topic must expand to include a broader range of research subjects. During two years of methodical discussions and workshops conducted through the interdisciplinary postdoctoral research group Sustainable Future at the Universitat Hamburg (Germany), the authors have observed that SD has played a major role in natural sciences (i.e. environmental and earth system sciences) and engineering, and a far lesser role in the social sciences and humanities (SSH). This imbalance in the discourse on SD in research impedes a full understanding of the diverse tasks and challenges that must be addressed in SD. An integrated approach is suggested to unite perspectives from natural sciences, engineering and SSH. The authors therefore encourage a more explicit notion of the concept of SD in SSH research, which builds upon and goes beyond current approaches to SD in SSH. The paper presents some illustrative examples which investigate the implications of expanding or restricting the disciplinary boundaries of sustainability research. The examples advocate an inclusive approach for which the authors describe and clarify several methods for expanding research towards cross-disciplinary methods. To this end, the authors present some practical recommendations for the integration of sustainability into the design and implementation of research academic practice. The paper closes up with an argument that all disciplines should expand their definition of sustainability in order to hasten research outcomes from all the diverse sectors of sustainability research.Part 1 - Curriculum Innovation.- Preparing teachers for sustainable development in higher education.- A Minor Programme on Sustainability for the Engineering Curriculum at the University of Chile.- Food for Thought: A University-wide Approach to Stimulate Curricular and Extracurricular ESD Activity.- Part 2 - Best Practice.- Embedding environmental sustainable development within social enterprise at the University of Northampton.- Improvements for a sustainable distance education with the new UNED on-site system for virtualization of exams: Malaga region (Andalucia, Spain) as case study.- Overview of the sustainability in Brazilian Information and Communications Technology market.

Greenhouse Gas Emissions and Management Practices that Affect Emissions in US Rice Systems

Previous reviews have quantified factors affecting greenhouse gas (GHG) emissions from Asian rice ( L.) systems, but not from rice systems typical for the United States, which often vary considerably particularly in practices (i.e., water and carbon management) that affect emissions. Using meta-analytic and regression approaches, existing data from the United States were examined to quantify GHG emissions and major practices affecting emissions. Due to different production practices, major rice production regions were defined as the mid-South (Arkansas, Texas, Louisiana, Mississippi, and Missouri) and California, with emissions being evaluated separately. Average growing season CH emissions for the mid-South and California were 194 (95% confidence interval [CI] = 129-260) and 218 kg CH ha season (95% CI = 153-284), respectively. Growing season NO emissions were similar between regions (0.14 kg NO ha season). Ratoon cropping (allowing an additional harvestable crop to grow from stubble after the initial harvest), common along the Gulf Coast of the mid-South, had average CH emissions of 540 kg CH ha season (95% CI = 465-614). Water and residue management practices such as alternate wetting and drying, and stand establishment method (water vs. dry seeding), and the amount of residue from the previous crop had the largest effect on growing season CH emissions. However, soil texture, sulfate additions, and cultivar selection also affected growing season CH emissions. This analysis can be used for the development of tools to estimate and mitigate GHG emissions from US rice systems and other similarly mechanized systems in temperate regions.

A long-term (2002 to 2017) record of closed-path and open-patheddy covariance CO 2 net ecosystem exchange fluxes from theSiberian Arctic

Ground-based observations of land–atmosphere fluxes are necessary to progressively improve global climate models. Observed data can be used for model evaluation and to develop or tune process models. In arctic permafrost regions, climate–carbon feedbacks are amplified. Therefore, increased efforts to better represent these regions in global climate models have been made in recent years. We present a multi-annual time series of land–atmosphere carbon dioxide fluxes measured in situ with the eddy covariance technique in the Siberian Arctic (7222 N, 12630 E). The site is part of the international network of eddy covariance flux observation stations (FLUXNET; site ID: Ru-Sam). The data set includes consistently processed fluxes based on concentration measurements of closed-path and open-path gas analyzers. With parallel records from both sensor types, we were able to apply a site-specific correction to open-path fluxes. This correction is necessary due to a deterioration of data, caused by heat generated by the electronics of open-path gas analyzers. Parameterizing this correction for subperiods of distinct sensor setups yielded good agreement between openand closed-path fluxes. We compiled a long-term (2002 to 2017) carbon dioxide flux time series that we additionally gap-filled with a standardized approach. The data set was uploaded to the Pangaea database and can be accessed through https://doi.org/10.1594/PANGAEA.892751. Published by Copernicus Publications. 222 D. Holl et al.: Long-term eddy covariance CO2 fluxes from the Siberian Arctic

Sustainable Internationalization? Measuring the Diversity of Internationalization at Higher Education Institutions

Sustainability and internationalization are considered to be core values of Higher Education Institutions (HEIs), but their relationship is rarely investigated. The current study develops a framework to create a sustainable internationalization policy for an HEI; it analyzes how to measure the sustainability of an internationalization policy in two steps. First, this study presents a theoretical framework for a cost-benefit analysis of HEIs’ sustainable internationalization policies using three sustainability pillars (economic, ecological, and social), each with examples for their own measurable indicators. Second, this research operationalizes the economic pillar of the framework to enable a specific measurement of the economic sustainability of internationalization. The empirical analysis identifies the distribution of funding for internationalization as a promising indicator. To demonstrate the implementation of this part of the framework, this study analyzes how German HEIs distribute their monetary investments in internationalization activities to countries worldwide. Using data from the German academic exchange service (DAAD), this research investigates the distribution using descriptive statistics. In a second step, the methodology of the Lorenz curve is empirically applied to the distribution of funding. Universitat Hamburg is used as a case study to visualize the different funding tendencies among German HEIs. The findings suggest that the distribution of resources for internationalization says more about the sustainable character of an HEI than the absolute amount of invested resources. To evaluate the sustainability of an HEI’s internationalization strategy, it is therefore necessary to look at the distribution of target countries in addition to the mere absolute level of funding.