Behaviors of the Yukon River Sediment Plume in the Bering Sea: Relations to Glacier-Melt Discharge and Sediment Load

Abstract

Sediment plumes, released to the Bering Sea from the delta front of the Yukon River, Alaska, are initiated mainly by glacier-melt sediment runoffs in the glacierized regions of the Yukon River drainage basin. The surface sediment plumes are extended around the fan-shaped Yukon River delta, which is followed by the northwestward dispersion. During continuous measurements of the Yukon River discharge and sediment load, behaviors of the sediment plumes were explored by shipboard and coastal observations in the Bering Sea. At the high river sediment load of ca. 2500 kg/s, the plume partially plunged into the sea bottom layer. The plunging probably originated in the nepheloid-layer formation from the flocculation of river-suspended sediment, of which more than 90% wt. is silt and clay (grain size d < 63 μm). In order to numerically obtain the area of the surface sediment plumes, a satellite image analysis was performed by using three near-infrared bands in MODIS/Aqua or MODIS/Terra. The plume area was significantly correlated (R2 = 0.735, p < 0.01) to the sediment load averaged for the two days with time lags of 20 days and 21 days to the date of a certain satellite image. Hence, the dispersion of plume-suspended sediment appears to be controlled by the sediment runoff events in the Yukon River rather than the northward “Alaskan Coastal Water”.

Plume motion characterization in unmanned aerial vehicle aerial video and imagery

“…Plumes, naturally generated or invoked by human activity, have been studied by multiple researchers for many years. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Johansen et al released two different dyes in a Red Sea location to study coastal water flow dynamics. The group tracked the dye plumes with an unmanned aerial vehicle (UAV) and high spatial-resolution SkySat satellite imagery using object detection, region growing, and AI methods.…”

“…The group tracked the dye plumes with an unmanned aerial vehicle (UAV) and high spatial-resolution SkySat satellite imagery using object detection, region growing, and AI methods. 1 Chikita et al 2 used satellite imagery in a Bering Sea location to investigate the natural plume generated by the Yukon River in Alaska and compared it with melting glacier discharge. Using three near-infrared bands from MODIS/Aqua or MODIS/Terra imagery, the authors estimated the surface plume area and found that there was a linear relationship between the plume area and the averaged sediment load.…”

“…Plumes, naturally generated or invoked by human activity, have been studied by multiple researchers for many years 1 – 19 Johansen et al. released two different dyes in a Red Sea location to study coastal water flow dynamics.…”

“…The group tracked the dye plumes with an unmanned aerial vehicle (UAV) and high spatial-resolution SkySat satellite imagery using object detection, region growing, and AI methods 1 . Chikita et al 2 . used satellite imagery in a Bering Sea location to investigate the natural plume generated by the Yukon River in Alaska and compared it with melting glacier discharge.…”

Sea Surface Salinity Variability in the Bering Sea in 2015–2020

“…In parallel, coastal river discharge becomes important in summer. The Yukon River and the Kuskokwim River are the major sources for freshwater, and their plumes create sharp salinity gradients [15][16][17][18]. With the breakdown of the inner front in late summer, this low-salinity signature spreads out over the shelf [19].…”