Abstract
Abstract. The Yenisei and Khatanga rivers are among the largest estuarine rivers that inflow to the Arctic Ocean. Discharge of the Yenisei River is 1 order of magnitude larger than that of the Khatanga River. However, spatial scales of buoyant plumes formed by freshwater runoff from the Yenisei and Khatanga gulfs are similar. This feature is caused by different tidal forcing in these estuaries, which have similar sizes, climate conditions, and geomorphology. The Khatanga discharge experiences strong tidal forcing that causes formation of a diluted bottom-advected plume in the Khatanga Gulf. This deep and weakly stratified plume has a small freshwater fraction and therefore occupies a large area on the shelf. The Yenisei Gulf, on the other hand, is a salt-wedge estuary that receives a large freshwater discharge and is less affected by tidal mixing due to low tidal velocities. As a result, the low-salinity and strongly stratified Yenisei plume has a large freshwater fraction and its horizontal size is relatively small. The results show that estuarine tidal mixing determines freshwater fraction in these river plumes, which governs their depth and area after they spread from estuaries to coastal sea. Therefore, the influence of estuarine mixing on spatial scales of a large river plume can be of the same importance as the roles of river discharge rate and wind forcing. In particular, plumes with similar areas can be formed by rivers with significantly different discharge rates, as illustrated by the Yenisei and Khatanga plumes.
Highlights
River plumes play an important role in land-ocean interactions
We address the Yenisei and Khatanga plumes formed by discharge of the large estuarine rivers to the Kara and Laptev seas
Based on tidal level and velocity data, tidal modeling, in situ measurements, and satellite observations, we demonstrate that estuarine tidal mixing conditions strongly affect vertical structure and spatial extent of the Yenisei and Khatanga plumes
Summary
River plumes play an important role in land-ocean interactions. Despite their relatively small volume as compared to adjacent coastal seas, they significantly affect global fluxes of buoyancy, heat, terrigenous sediments, nutrients, and anthropogenic pollutants, which are discharged to the coastal ocean with continental runoff (Dagg et al, 2004; Milliman and Farnsworth, 2011; Lebreton et al, 2017; Schmidt et al, 2017). The related processes of mixing of river runoff with seawater and formation of river plumes in estuaries determine their structure and govern their
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