Abstract
River discharge is the main source of terrigenous sediments in many coastal areas adjacent to estuaries and deltas of large rivers. Spreading and mixing dynamics of river plumes governs transport of suspended sediments and their deposition at sea bottom at these areas. Generally river plumes have very large synoptic and seasonal variability, which cannot be reconstructed from structure of bottom sediments due to their small accumulation velocity. However, bottom sediments can be indicative of variability of river plumes on inter-annual and decadal time scales. In this study we focus on the large Ob and Yenisei buoyant plumes formed in the central part of the Kara Sea. These plumes interact and mix in the area adjacent to the closely located Ob and Yenisei gulfs. Suspended sediments carried by these river plumes have significantly different geochemical characteristics that can be used to detect Ob or Yenisei origin of bottom sediments. Using new geochemical methods we revealed dependence between spreading patterns of these plumes and spatial distribution and vertical structure of bottom sediments in the study area. This relation is confirmed by a good agreement between local wind and discharge conditions reconstructed for 1948–2001 and vertical structure of bottom sediments.
Highlights
The Yenisei and Ob rivers are the first and the third largest Arctic rivers, their basin areas are 2580000 and 2990000 km[2]
River plumes have very large synoptic and seasonal variability[31,32,33,34], which cannot be reconstructed from spatial distribution and vertical structure of bottom sediments due to their small accumulation velocity
Bottom sediments can be indicative of variability of river plume dynamics on inter-annual and decadal time scales, especially in coastal areas characterized by rapid sedimentation rates
Summary
The Yenisei and Ob rivers are the first and the third largest Arctic rivers, their basin areas are 2580000 and 2990000 km[2]. We detect several layers of mixed Ob-Yenisei origin at the bottom sediment core samples collected in the Yenisei Gulf which are indicative of long-term periods of frequent intrusion of the Ob plume into the Yenisei Gulf described above.
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