Jason S. Lessels
University of Aberdeen
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Featured researches published by Jason S. Lessels.
Water Resources Research | 2016
Claire Tunaley; Doerthe Tetzlaff; Jason S. Lessels; Chris Soulsby
Acknowledgments The authors would like to thank our NRI colleagues for all their help with field and laboratory work, especially Audrey Innes, Jonathan Dick, and Ann Porter. We would like to also thank Iain Malcolm (Marine Scotland Science) for providing AWS data and the European Research Council ERC (project GA 335910 VEWA) for funding the VeWa project. Please contact the authors for access to the data used in this paper. We would also like to thank the Natural Environment Research Council NERC (project NE/K000268/1) for funding.
Water Resources Research | 2016
Jason S. Lessels; Doerthe Tetzlaff; Christian Birkel; Jonathan Dick; Chris Soulsby
Abstract Mixing of waters within riparian zones has been identified as an important influence on runoff generation and water quality. Improved understanding of the controls on the spatial and temporal variability of water sources and how they mix in riparian zones is therefore of both fundamental and applied interest. In this study, we have combined topographic indices derived from a high‐resolution Digital Elevation Model (DEM) with repeated spatially high‐resolution synoptic sampling of multiple tracers to investigate such dynamics of source water mixing. We use geostatistics to estimate concentrations of three different tracers (deuterium, alkalinity, and dissolved organic carbon) across an extended riparian zone in a headwater catchment in NE Scotland, to identify spatial and temporal influences on mixing of source waters. The various biogeochemical tracers and stable isotopes helped constrain the sources of runoff and their temporal dynamics. Results show that spatial variability in all three tracers was evident in all sampling campaigns, but more pronounced in warmer dryer periods. The extent of mixing areas within the riparian area reflected strong hydroclimatic controls and showed large degrees of expansion and contraction that was not strongly related to topographic indices. The integrated approach of using multiple tracers, geospatial statistics, and topographic analysis allowed us to classify three main riparian source areas and mixing zones. This study underlines the importance of the riparian zones for mixing soil water and groundwater and introduces a novel approach how this mixing can be quantified and the effect on the downstream chemistry be assessed.
Journal of Geophysical Research | 2016
Lorna E. Street; Joshua F. Dean; Michael F. Billett; Robert Baxter; Kerry J. Dinsmore; Jason S. Lessels; Jens-Arne Subke; Doerthe Tetzlaff; Philip A. Wookey
The linkages between methane production, transport, and release from terrestrial and aquatic systems are not well understood, complicating the task of predicting methane emissions. We present novel data examining the potential for the saturated zone of active layer soils to act as a source of dissolved methane to the aquatic system, via soil water discharge, within a headwater catchment of the continuous permafrost zone in Northern Canada. We monitored redox conditions and soil methane concentrations across a transect of soil profiles from midstream to hillslope and compare temporal patterns in methane concentrations in soils to those in the stream. We show that redox conditions in active layer soils become more negative as the thaw season progresses, providing conditions suitable for net methanogenesis and that redox conditions are sensitive to increased precipitation during a storm event—but only in shallower surface soil layers. While we demonstrate that methane concentrations at depth in the hillslope soils increase over the course of the growing season as reducing conditions develop, we find no evidence that this has an influence on stream water methane concentrations. Sediments directly beneath the stream bed, however, remain strongly reducing at depth throughout the thaw season and contain methane at concentrations 5 orders of magnitude greater than those in hillslope soils. The extent of substreambed methane sources, and the rates of methane transport from these zones, may therefore be important factors determining headwater stream methane concentrations under changing Arctic hydrologic regimes.
Journal of Geophysical Research | 2016
Lorna E. Street; Joshua F. Dean; Michael F. Billett; Robert Baxter; Kerry J. Dinsmore; Jason S. Lessels; Jens-Arne Subke; Doerthe Tetzlaff; Philip A. Wookey
The linkages between methane production, transport, and release from terrestrial and aquatic systems are not well understood, complicating the task of predicting methane emissions. We present novel data examining the potential for the saturated zone of active layer soils to act as a source of dissolved methane to the aquatic system, via soil water discharge, within a headwater catchment of the continuous permafrost zone in Northern Canada. We monitored redox conditions and soil methane concentrations across a transect of soil profiles from midstream to hillslope and compare temporal patterns in methane concentrations in soils to those in the stream. We show that redox conditions in active layer soils become more negative as the thaw season progresses, providing conditions suitable for net methanogenesis and that redox conditions are sensitive to increased precipitation during a storm event—but only in shallower surface soil layers. While we demonstrate that methane concentrations at depth in the hillslope soils increase over the course of the growing season as reducing conditions develop, we find no evidence that this has an influence on stream water methane concentrations. Sediments directly beneath the stream bed, however, remain strongly reducing at depth throughout the thaw season and contain methane at concentrations 5 orders of magnitude greater than those in hillslope soils. The extent of substreambed methane sources, and the rates of methane transport from these zones, may therefore be important factors determining headwater stream methane concentrations under changing Arctic hydrologic regimes.
Hydrological Processes | 2016
Chris Soulsby; John H. Bradford; Jonathan Dick; James P. McNamara; Josie Geris; Jason S. Lessels; M. Blumstock; Doerthe Tetzlaff
Biogeochemistry | 2016
Joshua F. Dean; Michael F. Billett; Robert Baxter; Kerry J. Dinsmore; Jason S. Lessels; Lorna E. Street; Jens-Arne Subke; Doerthe Tetzlaff; Ian Washbourne; Philip A. Wookey
Hydrological Processes | 2015
Jason S. Lessels; Doerthe Tetzlaff; Sean K. Carey; Pete Smith; Chris Soulsby
Environmental Research Letters | 2017
Joshua F. Dean; Y. van der Velde; Mark H. Garnett; Kerry J. Dinsmore; Robert Baxter; Jason S. Lessels; Pete Smith; Lorna E. Street; Jens-Arne Subke; Doerthe Tetzlaff; Ian Washbourne; Philip A. Wookey; Michael F. Billett
Water Resources Research | 2016
Claire Tunaley; Doerthe Tetzlaff; Jason S. Lessels; Chris Soulsby
Water Resources Research | 2016
Jason S. Lessels; Doerthe Tetzlaff; Christian Birkel; Jonathan Dick; Chris Soulsby