Abstract
The Arctic Ocean is of central importance for the global climate and ecosystem. It is a region undergoing rapid climate change, with a dramatic decrease in sea ice cover over recent decades. Surface advective pathways connect the transport of nutrients, freshwater, carbon and contaminants with their sources and sinks. Pathways of drifting material are deformed under velocity strain, due to atmosphere-ocean-ice coupling. Deformation is largest at fine space- and time-scales and is associated with a loss of potential predictability, analogous to weather often becoming unpredictable as synoptic-scale eddies interact and deform. However, neither satellite observations nor climate model projections resolve fine-scale ocean velocity structure. Here, we use a high-resolution ocean model hindcast and coarser satellite-derived ice velocities, to show: that ensemble-mean pathways within the Transpolar Drift during 2004–14 have large interannual variability and that both saddle-like flow structures and the presence of fine-scale velocity gradients are important for basin-wide connectivity and crossing time, pathway bifurcation, predictability and dispersion.
Highlights
The Arctic Ocean is of central importance for the global climate and ecosystem
Ever since Fridtjof Nansen identified the Transpolar Drift (TPD) by joining up occasional observations of surface debris (Siberian driftwood; the wreckage of another expedition ship, Jeannette) in the Arctic in the 1890s and used it to plan the route of the Fram Expedition[1], it has been assumed that this surface drift pathway is a relatively steady and clearly identifiable feature, connecting the East Siberian Arctic Shelf (ESAS) to east Greenland/Fram Strait, passing close to the North Pole (Fig. 1)
Previous studies examined buoys drifting in sea ice within the TPD2 and showed that the velocity may occasionally reverse and that there was substantial temporal variability associated with atmospheric synoptic circulation
Summary
The Arctic Ocean is of central importance for the global climate and ecosystem. It is a region undergoing rapid climate change, with a dramatic decrease in sea ice cover over recent decades. We use a high-resolution ocean model hindcast and coarser satellitederived ice velocities, to show: that ensemble-mean pathways within the Transpolar Drift during 2004–14 have large interannual variability and that both saddle-like flow structures and the presence of fine-scale velocity gradients are important for basin-wide connectivity and crossing time, pathway bifurcation, predictability and dispersion. Previous studies examined buoys drifting in sea ice within the TPD2 and showed that the velocity may occasionally reverse and that there was substantial temporal variability associated with atmospheric synoptic circulation. A more recent study using satellite and buoy observations linked substantial variability of the TPD and Beaufort Gyre, and the interplay between their strength and shifting position, to the patterns of atmospheric circulation[3]. In October 2019 the largest polar expedition yet undertaken, the international
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