Water ages in the critical zone of long-term experimental sites in northern latitudes

We thank Pernilla Löfvenius (SLU) for providing PET data for Krycklan (via SITES) and Carl Mitchell for snowmelt data in Dorset. We thank Pertti Ala-aho, Paolo Benettin, Sylvain Kuppel, Aaron A. Smith, and Hailong Wang for constructive discussions on the topic. The authors would like to acknowledge the support of the Maxwell computing cluster funded by the University of Aberdeen. The Krycklan component of the study was funded by the KAW Branch-Point project. We thank the European Research Council (ERC, project GA 335910 VeWa) for funding. We acknowledge support by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin. We thank Todd Walter and two anonymous referees for their critical comments to improve the manuscript. Data availability. The underlaying research data are not publicly available in a repository, as they contain 70 GB. However, they can be requested from the authorsPeer reviewedPublisher PD

Tracer-based assessment of flow paths, storage and runoff generation in northern catchments : a review

Peer reviewedPostprin

Measuring and Modeling Stable Isotopes of Mobile and Bulk Soil Water

We thank Audrey Innes for support with the isotope analysis at University of Aberdeen for the Bruntland Burn and Krycklan sites, Johannes Tiwari (SLU) for the isotope sampling in Krycklan, Pernilla Löfvenius (SLU) for providing PET data for Krycklan, Pertti Ala-aho for providing snowmelt simulations for Krycklan, and Kimberely Janzen (University of Saskatoon) for soil water isotope analysis for the Dorset sites. The work at Krycklan was supported by KAW Branch-Points. We thank the European Research Council (ERC, project GA 335910 VeWa) for funding. We thank two anonymous reviewers and the associate editor for their suggestions and comments.Peer reviewedPublisher PD

Comparison of threshold hydrologic response across northern catchments

Funded by Leverhulme Trust. Grant Number: F/00 152/AGPeer reviewedPostprin

Cross-regional prediction of long-term trajectory of stream water DOC response to climate change

There is no scientific consensus about how dissolved organic carbon (DOC) in surface waters is regulated. Here we combine recent literature data from 49 catchments with detailed stream and catchment process information from nine well established research catchments at mid- to high latitudes to examine the question of how climate controls stream water DOC. We show for the first time that mean annual temperature (MAT) in the range from −3° to +10° C has a strong control over the regional stream water DOC concentration in catchments, with highest concentrations in areas ranging between 0° and +3° C MAT. Although relatively large deviations from this model occur for individual streams, catchment topography appears to explain much of this divergence. These findings suggest that the long-term trajectory of stream water DOC response to climate change may be more predictable than previously thought

Changing forest water yields in response to climate warming: results from long-term experimental watershed sites across North America

Climate warming is projected to affect forest water yields but the effects are expected to vary. We investigated how forest type and age affect water yield resilience to climate warming. To answer this question, we examined the variability in historical water yields at long-term experimental catchments across Canada and the United States over 5-year cool and warm periods. Using the theoretical framework of the Budyko curve, we calculated the effects of climate warming on the annual partitioning of precipitation (P) into evapotranspiration (ET) and water yield. Deviation (d) was defined as a catchment’s change in actual ET divided by P [AET/P; evaporative index (EI)] coincident with a shift from a cool to a warm period – a positive d indicates an upward shift in EI and smaller than expected water yields, and a negative d indicates a downward shift in EI and larger than expected water yields. Elasticity was defined as the ratio of inter annual variation in potential ET divided by P (PET/P; dryness index) to inter annual variation in the EI – high elasticity indicates low d despite large range in drying index (i.e., resilient water yields), low elasticity indicates high d despite small range in drying index (i.e., non-resilient water yields). Although the data needed to fully evaluate ecosystems based on these metrics are limited, we were able to identify some characteristics of response among forest types. Alpine sites showed the greatest sensitivity to climate warming with any warming leading to increased water yields. Conifer forests included catchments with lowest elasticity and stable to larger water yields. Deciduous forests included catchments with intermediate elasticity and stable to smaller water yields. Mixed coniferous/deciduous forests included catchments with highest elasticity and stable water yields. Forest type appeared to influence the resilience of catchment water yields to climate warming, with conifer and deciduous catchments more susceptible to climate warming than the more diverse mixed forest catchments

Changing forest water yields in response to climate warming: results from long-term experimental watershed sites across North America

Climate warming is projected to affect forest water yields but the effects are expected to vary. We investigated how forest type and age affect water yield resilience to climate warming. To answer this question, we examined the variability in historical water yields at long‐term experimental catchments across Canada and the United States over 5‐year cool and warm periods. Using the theoretical framework of the Budyko curve, we calculated the effects of climate warming on the annual partitioning of precipitation (P) into evapotranspiration (ET) and water yield. Deviation (d) was defined as a catchment's change in actual ET divided by P [AET/P; evaporative index (EI)] coincident with a shift from a cool to a warm period – a positive d indicates an upward shift in EI and smaller than expected water yields, and a negative d indicates a downward shift in EI and larger than expected water yields. Elasticity was defined as the ratio of interannual variation in potential ET divided by P (PET/P; dryness index) to interannual variation in the EI – high elasticity indicates low d despite large range in drying index (i.e., resilient water yields), low elasticity indicates high d despite small range in drying index (i.e., nonresilient water yields). Although the data needed to fully evaluate ecosystems based on these metrics are limited, we were able to identify some characteristics of response among forest types. Alpine sites showed the greatest sensitivity to climate warming with any warming leading to increased water yields. Conifer forests included catchments with lowest elasticity and stable to larger water yields. Deciduous forests included catchments with intermediate elasticity and stable to smaller water yields. Mixed coniferous/deciduous forests included catchments with highest elasticity and stable water yields. Forest type appeared to influence the resilience of catchment water yields to climate warming, with conifer and deciduous catchments more susceptible to climate warming than the more diverse mixed forest catchments