The new study is reconstructing the path of dead trees (driftwood) as they crossed the Arctic Ocean for over 500 years, giving scientists a unique perspective on the changes in sea ice and currents over the past half-millennium.
Scientists have presented a 500-year history of driftwood arriving to the shores of northern Svalbard. Driftwood in the Arctic results from dying trees being trapped in large rivers, depleting circum-Arctic land masses, which, when they flow into the Arctic Ocean, can get stuck, forming sea ice. This allows wood to move across the Arctic Ocean without sinking, making it an invaluable indicator of sea ice extent by recording changes in Arctic Ocean surface currents (and therefore sea ice drift) and ice cover. By comparing the tree ring width (TRW) measurements of these driftwood samples with the TRW series for trees in boreal forests, the scientists determined the region from which each sample was obtained. Thus, it is possible to approximately determine its probable trajectory through the Arctic Ocean. Arctic sea ice is rapidly shrinking in size and thickness, affecting local and global climatic and environmental conditions. Knowledge of past changes is necessary to place this current trend in a broader context to assist in future projections for Arctic sea ice. The data are consistent with observations of Arctic Ocean surface circulation patterns and climatic conditions, confirming the use of driftwood as a proxy for Arctic Ocean surface currents and sea ice dynamics.
The new study found a clear decline in the number of new driftwood over the past 30 years, reflecting a dramatic reduction in sea ice in the warming Arctic and providing a better picture of past conditions in the Arctic Ocean than other methods allow. The study is published in the Journal of Geophysical Research: Oceans.