When it comes to climate change, researchers have used a wide range of methods to understand the history of our planet on a global scale. We’ve talked before about using the movement and diets of animals, the location of mangroves, and ice cores to track just how climate has changed over time periods and around various locations, and this next story uses another method – tracking driftwood in the Arctic.

A new study in the Journal of Geophysical Research: Oceans and led by Georgia Hole retraces the journey of driftwood that has washed up on the shores of Svalbard, a Norwegian archipelago in the Arctic Circle. This journey allowed the researchers to reconstruct the level of sea ice and changes in the currents. As Hole notes: This is the first time driftwood has been used to look at large-scale changes in Arctic sea ice dynamics and circulation patterns.

The press release goes on to explain: The Arctic Ocean collects trees that naturally fall into high-latitude rivers in North America and Eurasia. When it was cold enough, some of the trees were frozen into the sea ice. The ice then floated across the ocean, swept along by ocean currents and winds, until beaching on Svalbard’s shores. There they sat, some for hundreds of years, until researchers like Hole…came along.

The team collected driftwood and then analyzed the tree rings back in the lab. As we’ve mentioned before, there is a huge database of tree rings called the International Tree-Ring Data Bank, and the tree rings in the driftwood were compared to samples of Arctic forests already in that database. This allowed Hole to match trees to their originating countries and watersheds and see how the sources of the driftwood varied over time.

Combining that tree ring data with the earliest recorded sea ice observations from 1600 to 1850 and the more recent airplane and satellite imagery, and it was possible to analyze the driftwood patterns for changes in the sea ice. The data shows that the lowest-latitude sea ice, the ice in the warmest regions of the Arctic, moved steadily northward. This means the climate was warming and the ice was melting, which made it less likely for driftwood to be carried across the Arctic on the sea ice. As Hole explains: We also saw an increase in variability in the driftwood record from 1700 to 1850, which we interpret as increased variability in sea ice.

When it’s colder, there is more sea ice for the driftwood to travel upon, and the sources of the driftwood had greater variability than during times when the climate warmed and the ice melted.

This just goes to show that so many aspects of our planet are affected by climate change, and sea ice in particular seems to be very fragile.

More Information

AGU press release

“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,” Georgia M. Hole et al., 2021 September 15, JGR Oceans