Freshwater pearl mussels from northern Sweden serve as long-term, high-resolution stream water isotope recorders

• Main Authors: Schöne, Bernd R., Meret, Aliona E., Baier, Sven M., Fiebig, Jens, Esper, Jan, McDonnell, Jeffrey, Pfister, Laurent
• Format: Text
• Language: English
• Published: 2019
• Subjects: Arctic; North Atlantic; North Atlantic oscillation; North Sweden; Northern Sweden
• Online Access: https://doi.org/10.5194/hess-2019-337; https://www.hydrol-earth-syst-sci-discuss.net/hess-2019-337/

The stable isotope composition of lacustrine sediments is routinely used to infer Late Holocene changes in precipitation over Scandinavia and ultimately, atmospheric circulation dynamics in the North Atlantic realm. However, such archives provide only low temporal resolution (ca. 15 years) precluding the ability to identify changes on inter-annual and quasi-decadal time-scales. Here we present a new, high-resolution reconstruction using shells of freshwater pearl mussels, Margaritifera margaritifera , from three rivers in north Sweden. We present seasonally to annually resolved, calendar-aligned stable oxygen and carbon isotope data from ten specimens covering the time interval of 1819 to 1998. The studied bivalves formed their shells near equilibrium with the oxygen isotope signature of ambient water and thus reflected hydrological processes in the catchment as well as changes, albeit damped, of the isotope value of local atmospheric precipitation. Shell oxygen isotopes were correlated significantly with the North Atlantic Oscillation index (up to 56 % explained variability) suggesting that moisture from which winter precipitation formed originated predominantly in the North Atlantic during NAO + years, but in the Arctic during NAO – years. The specific isotope signature of winter precipitation was damped in stream water and this effect was recorded by the shells. Shell stable carbon isotope values did not show consistent ontogenetic trends, but rather oscillated around an average that differed slightly among the studied rivers (ca. −12.00 to −13.00 ‰). Results of this study contribute to an improved understanding of climate dynamics in Scandinavia and the North Atlantic sector and can help to constrain ecological changes in riverine ecosystems. Moreover, long isotope records of precipitation and streamflow are pivotal for improving our understanding and modeling of hydrological, ecological, biogeochemical and atmospheric processes. Our new approach offers a much higher temporal resolution and superior dating control than existing archives.