A modeling study of wind modulation of the strength and extent of the Yukon River plume

Abstract:

The Yukon River is one of the largest rivers in North America and contributes large quantities of freshwater and terrigenous material to the coastal ocean. The mean currents at the outflow of the Yukon in the northern Bering Sea flow north through the Bering Strait and into the Arctic Ocean, contributing to the freshwater budget of the Arctic. This study describes and applies a new 3-Dimensional hydrodynamic model across 7 years to investigate the variability in coastal currents and distribution of freshwater from the Yukon river into the coastal ocean. The dynamic environment is surprisingly consistent in the dominant hydrographic features, with an anticyclonic eddy that is a common feature of large river plumes with relatively small estuaries. Across years, metrics in the river plume related to the input of freshwater were quantified in multiple wind regimes. A metric of river plume mass-area (RPMA) that is derived from the horizontal variability in the vertical density gradient is presented. RPMA is closely related to the plume strength and extent, and principle component analysis shows a relationship to cumulative discharge over the previous ten days. On shorter time scales (days to weeks) wind variability in both direction and magnitude exerts influence on the structure of the river plume and overall amount of freshwater dispersion that occurs along the coast. The variability in plume dispersion due to wind forcing has implications for where terrigenous material within plume waters is dispersed in the northern Bering Sea.