A driftwood-based record of Arctic sea ice during the last 500 years
from northern Svalbard reveals sea ice dynamics in the Arctic Ocean and
Arctic peripheral seas
Abstract
We 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 towards regions covered by
the reference chronologies. Our study considers alternate approaches to
selecting probable origin sites, by weighting scores via reference
chronology span and visualising results through spatiotemporal density
plots, as opposed to more basic ranking systems. As our samples come
from naturally felled trees (as opposed to logged, or both), the
relative proportions of different provenances are used to infer past
ocean current dominance. Our record indicates centennial-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 tracks the
northward seasonal ice formation shift and migration of seasonal sea ice
to the 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 robust proxy for Arctic Ocean
surface current and sea ice dynamics.