The Transpolar Drift in the Central Arctic Ocean as Measured by AON Observations
Abstract:The Transpolar Drift of sea ice across Arctic Ocean was arguably the first major element of Arctic Ocean circulation to be discovered. Nansen’s plan for his pioneering Fram expedition was based on the observation of the drift of the wreckage of the De Long’s ill-fated Jeanette from near Wrangle Island to the southern coast of Greenland. In this context the Transpolar Drift characterizes the large-scale motion of sea ice, but the term can be applied to the geostrophic circulation of the upper ocean as well. The Transpolar Drift of sea ice and upper ocean are related because both are driven, at least in part, by the gradient in dynamic ocean topography (DOT, sea surface height - geoid) associated with the Transpolar Front between Pacific and Atlantic-derived waters.
Starting in the 1990s, major changes in direction of the ocean and ice transpolar drifts characterized shifts between anticyclonic and cyclonic ocean circulation. These affect the dominant pathways of ice, freshwater, and chemical constituents through Arctic Basin. Consequently, tracking behavior of the Transpolar Drift has been a high priority for the AON North Pole Environmental Observatory (NPEO). Recent hydrographic sections across the 90°E (from NPEO) and 90°W (from the Switchyard Project) longitude lines mainly straddle the Drift so that dynamic heights derived from the hydrography can be used as a proxy for DOT, and annual sections of geostrophic velocity determined. Sections along 0° and 180° longitude usually cross the Transpolar Front and Drift at a more oblique angle but provide a measure of Transpolar Drift direction. Hydrography results will be compared with DOT from satellite remote sensing, optimally interpolated satellite and buoy-derived ice drift, and changes in chemical constituents to describe the significance of and recent changes in the Transpolar Drift.