Abstract
AbstractWe present a 500‐year history of naturally felled driftwood incursion to northern Svalbard, directly reflecting regional sea ice conditions and Arctic Ocean circulation. Provenance and age determinations by dendrochronology and wood anatomy provide insights into Arctic Ocean currents and climatic conditions at a fine spatial resolution, as crossdating with reference chronologies from the circum‐Arctic boreal forests enables determination of the watershed the driftwood originated from. Sample crossdating may result in a wide range of matches across the pan‐boreal region, which may be biased toward regions covered by the reference chronologies. Our study considers alternate approaches to selecting probable origin sites, by weighting scores via reference chronology span and visualizing results through spatiotemporal density plots, as opposed to more basic ranking systems. As our samples come from naturally felled trees (not logged or both), the relative proportions of different provenances are used to infer past ocean current dominance. Our record indicates centennial‐to decadal‐scale shifts in source regions for driftwood incursion to Svalbard, aligning with Late Holocene high variability and high frequency shifts in the Transpolar Drift and Beaufort Gyre strengths and associated fluctuating climate conditions. Driftwood occurrence and provenance also track the northward ice formation shift in peripheral Arctic seas in the past century. A distinct decrease in driftwood incursion during the last 30 years matches the observed decline in pan‐Arctic sea ice extent in recent decades. Our new approach successfully employs driftwood as a proxy for Arctic Ocean surface circulation and sea ice dynamics.
Highlights
The Arctic is vulnerable to climatic changes on a range of temporal and spatial scales from geological to inter-annual, and a hotspot of warming under modern climate change due to the Arctic Amplification (Serreze & Francis, 2006) — a term for the feedbacks and interactions from the region's sea ice and snow cover resulting in enhanced and accelerated greenhouse gas-induced warming in the Arctic
Dynamic processes affecting the Arctic Ocean such as the Arctic Oscillation (AO) are being increasingly examined for their impact on ocean circulation and sea ice dynamics (e.g., Barnes & Screen, 2015; Comiso & Hall, 2014; Ding et al, 2017; Hole & Macias-Fauria, 2017; Rigor et al, 2002)
We present a 500-year history of driftwood incursion to Northern Svalbard reflecting associated sea ice and Arctic Ocean circulation and provide for the first time a direct evaluation of sea ice dynamics inferred from naturally felled driftwood against the observational record
Summary
The Arctic is vulnerable to climatic changes on a range of temporal and spatial scales from geological to inter-annual, and a hotspot of warming under modern climate change due to the Arctic Amplification (Serreze & Francis, 2006) — a term for the feedbacks and interactions from the region's sea ice and snow cover resulting in enhanced and accelerated greenhouse gas-induced warming in the Arctic. The continuing decline in sea ice cover is expected to result in wide-ranging consequences impacting the Arctic and beyond These include impacts on terrestrial and marine productivity, changes to global atmospheric and ocean circulation patterns, increased temperatures and rainfall, terrestrial fauna and flora population fragmentation and habitat reduction, increased marine species interaction and connectivity, and northward expansion of lower-latitude species (Bintanja & Andry, 2017; Bjorkman et al, 2020; Francis & Vavrus, 2012; Macias-Fauria & Post, 2018; Overland & Wang, 2010; Overland et al, 2016; Post & Høye, 2013; Screen & Simmonds, 2010, 2014; Vavrus et al, 2017). Reconstructions of sea ice preceding observations commonly utilize ocean sedimentary core data Such records are, limited in spatiotemporal resolution due to low sedimentation rates in the central Arctic Ocean (Backman et al, 2004; Polyak et al, 2010), limiting their insight into sea ice fluctuations at the sub-millennial scale. Further knowledge of past sea ice dynamics is needed to understand the context of recent change and gain insight into possible future sea ice trajectories under conditions of increasing global average temperatures
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