Flushing or mixing? Stable water isotopes reveal differences in arctic forest and peatland soil water seasonality

Muhic, Filip; Ala‐aho, Pertti; Noor, Kashif; Welker, Jeffrey M.; Kløve, Bjørn; Marttila, Hannu

doi:10.1002/hyp.14811

Cited by 3 publications

(1 citation statement)

References 216 publications

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“…Furthermore, while regional studies are not uncommon for lake water isotopes, similar systematic efforts are limited for soil water isotopes, meaning there is a gap in observations for the growth water utilized by terrestrial plants as it isotopically relates to precipitation. Most calibration work for compound-specific water isotope proxies (e.g., n-alkyl lipids) use mean annual precipitation (e.g., Sachse et al, 2012) yet there are local observations that demonstrate Arctic soil water can be seasonally-biased (Cooper et al, 1991;Throckmorton et al, 2016;Bush et al, 2017;McFarlin et al, 2019;Muhic et al, 2023) and/or evaporatively enriched (Tetzlaff et al, 2018;Eensalu et al, 2023). It is also common to assume that terrestrial plant growth water is restricted to seasonal precipitation because Arctic plant growth is limited to late spring and summer (e.g., Balascio et al, 2013;Curtin et al, 2019;Kjellman et al, 2020;Thomas et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal variation of modern lake, stream, and soil water isotopes in Iceland

Harning,

Raberg,

McFarlin

et al. 2024

Preprint

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Abstract. As global warming progresses, changes in high-latitude precipitation are expected to impart long-lasting impacts on earth systems, including glacier mass balance and ecosystem structure. Reconstructing past changes in high-latitude precipitation and hydroclimate from networks of continuous lake records offers one way to improve forecasts of precipitation and precipitation-evaporation balances, but these reconstructions are currently hindered by the incomplete understanding of controls on lake and soil water isotopes. Here, we study the distribution of modern water isotopes in Icelandic lakes, streams, and surface soils collected in 2002, 2003, 2004, 2014, 2019 and 2020 to understand the geographic, geomorphic, and environmental controls on their regional and interannual variability. We find that lake water isotopes in open-basin (through-flowing) lakes reflect local precipitation with biases toward the cold season, particularly in lakes with sub-annual residence times. Closed-basin lakes have water isotope and deuterium excess values consistent with evaporative enrichment. Interannual and seasonal variability of lake-water isotopes at repeatedly sampled sites are consistent with instrumental records of winter snowfall, summer relative humidity, and atmospheric circulation patterns, such as the North Atlantic Oscillation. In contrast to the cold-season bias in Icelandic lakes, summer surface soil water isotopes reflect summer precipitation overprinted by evaporative enrichment that can occur throughout the year, although the soils sampled were shallower than rooting depths for many plant types. This dataset provides new insight into the functionality of water isotopes in Icelandic environments and offers renewed possibilities for optimized site selection and proxy interpretation in future paleohydrological studies on this North Atlantic outpost.

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Section: Introductionmentioning

confidence: 99%

Spatiotemporal variation of modern lake, stream, and soil water isotopes in Iceland

Harning,

Raberg,

McFarlin

et al. 2024

Preprint

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Snow sampling strategy can bias estimation of meltwater fractions in isotope hydrograph separation

Noor,

Marttila,

Welker

et al. 2023

Journal of Hydrology

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Modeling snowpack dynamics and surface energy budget in boreal and subarctic peatlands and forests

Nousu,

Lafaysse,

Mazzotti

et al. 2024

The Cryosphere

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Abstract. The snowpack has a major influence on the land surface energy budget. Accurate simulation of the snowpack energy and radiation budget is challenging due to, e.g., effects of vegetation and topography, as well as limitations in the theoretical understanding of turbulent transfer in the stable boundary layer. Studies that evaluate snow, hydrology and land surface models against detailed observations of all surface energy balance components at high latitudes are scarce. In this study, we compared different configurations of the SURFEX land surface model against surface energy flux, snow depth and soil temperature observations from four eddy-covariance stations in Finland. The sites cover two different climate and snow conditions, representing the southern and northern subarctic zones, as well as the contrasting forest and peatland ecosystems typical for the boreal landscape. We tested different turbulent flux parameterizations implemented in the Crocus snowpack model. In addition, we examined common alternative approaches to conceptualize soil and vegetation, and we assessed their performance in simulating surface energy fluxes, snow conditions and soil thermal regime. Our results show that a stability correction function that increases the turbulent exchange under stable atmospheric conditions is imperative to simulate sensible heat fluxes over the peatland snowpacks and that realistic peat soil texture (soil organic content) parameterization greatly improves the soil temperature simulations. For accurate simulations of surface energy fluxes, snow and soil conditions in forests, an explicit vegetation representation is necessary. Moreover, we demonstrate the high sensitivity of surface fluxes to a poorly documented parameter involved in snow cover fraction computation. Although we focused on models within the SURFEX platform, the results have broader implications for choosing suitable turbulent flux parameterization and model structures depending on the potential use cases for high-latitude land surface modeling.

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Flushing or mixing? Stable water isotopes reveal differences in arctic forest and peatland soil water seasonality

Cited by 3 publications

References 216 publications

Spatiotemporal variation of modern lake, stream, and soil water isotopes in Iceland

Spatiotemporal variation of modern lake, stream, and soil water isotopes in Iceland

Snow sampling strategy can bias estimation of meltwater fractions in isotope hydrograph separation

Modeling snowpack dynamics and surface energy budget in boreal and subarctic peatlands and forests

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