Research Article
Predicted sea-ice loss will terminate Iceland's driftwood supply by 2060 CE

https://doi.org/10.1016/j.gloplacha.2022.103834Get rights and content

Highlights

  • Driftwood was and is the most important resource for all Arctic settlements.

  • Most of the Icelandic driftwood originates from the Yenisei catchment in central Siberia.

  • An abrupt decline in the amount of Icelandic driftwood supply occurred in the 1980s.

  • Icelandic driftwood supply will cease under predicted sea-ice loss by 2060 CE.

Abstract

Driftwood supply was a pivotal factor for the Norse expansion in medieval times and still exhibits an essential resource for Arctic settlements. The physical causes and societal consequences of long-term changes in the distribution of Arctic driftwood are, however, poorly understood. Here, we use dendrochronology to reconstruct the age and origin of 289 driftwood samples that were collected at remote shorelines in northeast Iceland. Based on 240 reference tree-ring width chronologies from the boreal forest zone, and an overall provenance success of 73%, we show that most of the driftwood is pine and larch from the Yenisei catchment in central Siberia. Our study reveals an abrupt decline in the amount of driftwood reaching Iceland since the 1980s, which is corroborated by the experience of local farmers and fishers. Despite the direct and indirect effects of changes in both, logging activity across Siberia as well as Arctic Ocean currents, the predicted amount of sea-ice loss under anthropogenic global warming is likely to terminate Iceland's driftwood supply by 2060 CE.

Introduction

Arctic driftwood was pivotal for the medieval Norse expansion across the European/North Atlantic sector (Alix, 2005, Alix, 2012, Alix, 2016; Mooney, 2016a; Pinta, 2018). Representing the only major wood resource in the treeless environment of the high-northern latitudes, driftwood was crucial for fire fuel, construction timber, boat building and a wide range of other routine items (Arnold, 1994; Gulløv, 1997; Hreinsson, 1997; Kristjánsdóttir et al., 2001; Le Mouël and LeMouël, 2002; Ljungqvist, 2005; Alix, 2009a, Alix, 2009b; Mooney, 2016a, Mooney, 2016b; Pinta, 2018; Omurova et al., 2020; Vanlandeghem et al., 2020). The dendrochronological and biochemical study of driftwood can provide unique insights into past human settlement patterns and environmental changes across the high-northern latitudes (Blanchette et al., 2016; Shumilov et al., 2020). Due to its high social and economic value, the amount of driftwood was carefully recorded by farmers and fishers along the Arctic coastlines (Fig. 1; Krisjansson, 1980; Johansen, 1999; Steelandt et al., 2013). To date, driftwood still plays an essential role for all human settlements beyond the northern treeline (Johansen, 1999; Shaw, 2012; Steelandt et al., 2013), where it is frequently used as firewood and building material (Claire and Brewster, 2004; Rekaviður, 2022, https://rekavidur.com/).

Due to natural riverbank erosion and industrial wood logging, huge amounts of driftwood enter the Arctic Ocean every year through the large boreal river systems (Eggertsson, 1993, Eggertsson, 1994; Johansen, 1998; Hellmann et al., 2017; Ahmed et al., 2020; Hole et al., 2021). After entering the Arctic Ocean, driftwood is usually ice-rafted for several years before being released from melting multiyear sea-ice, and deposited along the shallow coastlines of Greenland, Iceland, Svalbard, or the Canadian Archipelago (Häggblom, 1982; Steelandt et al., 2015; Hellmann et al., 2017; Dalaiden et al., 2018; Krumpen et al., 2019). The spatiotemporal supply of driftwood depends on the interplay of factors and processes in both, the boreal source and Arctic sink regions, as well as the complex transport pathways in-between (Fig. 2). These may include river discharge rates, logging and transport activities, permafrost thawing, floods, wildfires, ice and other dams, sea surface temperatures, surface winds, sea-ice extent and drift, water salinity, species-specific floating capacities of wood, as well as ocean currents, such as the Transpolar Drift and the Beaufort Gyre (Hole and Macias-Fauria, 2017; Sander et al., 2021; Tsubouchi et al., 2021). Furthermore, it has been argued that long-term climate and environmental changes have affected the dispersal of Arctic driftwood at different rates and intensities throughout the Holocene (Funder et al., 2011; Nixon et al., 2016). While driftwood was abundant on Ellesmere Island from around 10–6 k years BP, driftwood was particularly sparse in northern Greenland during the Holocene Thermal Maximum around 8–6 k years BP, because of reduced multiyear sea-ice and more open water (Funder et al., 2011). Conversely, a sudden increase in driftwood abundance along the shallow coastlines of Greenland and a decrease of such material on Ellesmere Island began after around 6 k years BP, whereas the past around 2.5 k years were characterized by centennial-scale fluctuations in the amount and origin of driftwood (Funder et al., 2011). As a rule of thumb, less driftwood supply is indicative of coastal blocking by persistent land-fast ice. The physical causes and societal consequences of long-term variation in the transportation and accumulation of Arctic driftwood are still unclear.

To gain deeper insights into the climate dependency of Icelandic driftwood supply, we analyse 289 tree-ring width series from conifers that were collected in 1989 and 2019 along remote shorelines in north-eastern Iceland (Fig. 2; Supplementary Table S1). We then combine our annually resolved and absolutely dated driftwood evidence with the output of state-of-the-art climate model simulations to assess the role of sea-ice extent for past and future changes in driftwood abundance across the North Atlantic/European sector.

Section snippets

Sampling

A total of 289 Arctic driftwood samples were collected during two sampling campaigns along the northern coastline of the almost uninhabited Langanes peninsula in north-eastern Iceland (66.38°N, 14.87°W). During the first sampling campaign in 1989, disc samples of 181 driftwood remains were collected, and another 108 samples were collected 30 years later in 2019. In both cases, the sampling focussed on large and old driftwood remains due to their higher probability for successful cross-dating.

Icelandic driftwood composition

Logged trees dominate our driftwood collection with 83%, whereas naturally fallen trees characterized by the presence of a root collar account for only 17% of all material (Fig. 4). The combination of precise wood anatomical species identification and dendrochronological cross-dating is necessary for tracing the origin of driftwood (Hellmann et al., 2017), which has often been neglected in the past (Funder et al., 2011; Hole et al., 2021). Composed of P. sylvestris (67%), Larix spp. (23%), and

Author contributions

T.K., M.R., O.E., P.C., T.Z. and U.B. collected driftwood. A.K., O.E. and U.B. provided the boreal reference chronologies. T.K., M.R., O.E. and H.V. processed the driftwood samples. T.C. performed the proxy-model comparison. T.K. and U.B. wrote and revised the paper with input from all others.

Data availability

The data are available on request from the corresponding author.

Declaration of Competing Interest

The authors declare no competing interests.

Acknowledgements

The work was supported by the Establishing bilateral cooperation with Icelandic forest service (EHP-BF10-OVNKM-1-023-01-2018, EEA and NORWAY GRANTS 2014–2021), the SustES project–Adaptation strategies for sustainable ecosystem services and food security under adverse environmental conditions (CZ.02.1.01/0.0/0.0/16_019/0000797), the ERC project Monostar (grant number AdG 882727), and Geografický výzkum dynamiky přírodních a společenských prostorových procesů (GEODYN)” (MUNI/A/1570/2020). Part of

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