Dropped in the Ocean – 87Sr/86Sr as a provenance tool for ice-rafted Arctic driftwood

Abstract

Provenance and age determinations of driftwood provide insights into Holocene Arctic Ocean surface currents and sea ice dynamics, with detailed reconstructions requiring a provenance methodology with fine temporal and spatial resolution. Determination of wood geographical provenance by genus data is limited by its spatially coarse resolution, while provenance by dendrochronological crossdating is reliant on available boreal forest reference chronologies which are abundant for recent centuries but more sparse for older periods of the Holocene. We present the development of novel techniques to refine the provenance of driftwood through radiogenic isotopic analysis ( 87 Sr/ 86 Sr). The use of geochemical techniques addresses limitations of current methods and opens the possibility of defining the role of atmospheric and oceanic circulation in sea ice and climatic changes throughout the Holocene at a finer spatial resolution than currently possible. This study investigates and develops geochemical 87 Sr/ 86 Sr fingerprinting of Arctic driftwood. To this end, it analyses driftwood samples from northern Svalbard and compares this technique with provenance regions obtained through dendrochronology, and with modelled and measured global 87 Sr/ 86 Sr reference databases. We conclude that the utilisation of 87 Sr/ 86 Sr ratios to establish provenance for Arctic driftwood has some potential, but identify important limitations in the method, concerning both the signal in samples and reference values required for provenance. Increased sample populations and source samples for calibration, as well as methodological improvements that address the likely overprinting linked to driftwood transport, are recommended to build upon this work. We conclude that at present dendro-provenancing continues to be the most powerful method to study sea ice dynamics from Arctic driftwood and suggest that given the high spatial granularity of 87 Sr/ 86 Sr across the boreal forest, this technique might only be usable in combination with previously developed provenance tools and reconstructions. This study provides a first step in the use of radiogenic isotopic analysis in a multi-proxy reconstruction of Holocene driftwood incursion onto high Arctic shorelines. • Driftwood is a novel tool for insights into Holocene Arctic sea ice dynamics. • Fine spatial and temporal resolution of driftwood provenance is needed. • Geochemical 87 Sr/ 86 Sr fingerprinting of Arctic driftwood is explored in this study. • 87 Sr/ 86 Sr shows some promise, with limitations in reference data and sample signals. • We conclude that a combined approach to driftwood provenance shows the most promise.