“…This area is characterized by extremely rapid sedimentation rate caused by the interaction and mixing between freshwater discharge and saline sea water 14,19–26 . Northward from this area salinity in the surface layer and sediment load sharply decrease 5,22,26 . The lithologic composition of bottom sediments is relatively homogenous for the southern part of the Yenisei Gulf.…”
Section: Resultsmentioning
confidence: 89%
“…Bottom sediments are mainly composed of pelitomorphic silt of olive-gray to black color with admixture of aleuritic and psammitic matter 21,23,24,26 . Due to extremely rapid accumulation of river-borne sediments, influence of coastal erosion on the local sediment input is relatively low that results in small share of coarse sediment fraction at the considered stations 22,27 .Figure 4Locations of the sediment samples of seafloor surface layer of the Yenisei (blue circles) and mixed (gray circles) origin in the Yenisei Gulf identified by the additive geochemical criterion (zoomed part of Fig. 3a), sizes of the circles represent absolute values of AGC O/Y .…”
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.
“…This area is characterized by extremely rapid sedimentation rate caused by the interaction and mixing between freshwater discharge and saline sea water 14,19–26 . Northward from this area salinity in the surface layer and sediment load sharply decrease 5,22,26 . The lithologic composition of bottom sediments is relatively homogenous for the southern part of the Yenisei Gulf.…”
Section: Resultsmentioning
confidence: 89%
“…Bottom sediments are mainly composed of pelitomorphic silt of olive-gray to black color with admixture of aleuritic and psammitic matter 21,23,24,26 . Due to extremely rapid accumulation of river-borne sediments, influence of coastal erosion on the local sediment input is relatively low that results in small share of coarse sediment fraction at the considered stations 22,27 .Figure 4Locations of the sediment samples of seafloor surface layer of the Yenisei (blue circles) and mixed (gray circles) origin in the Yenisei Gulf identified by the additive geochemical criterion (zoomed part of Fig. 3a), sizes of the circles represent absolute values of AGC O/Y .…”
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.
“…Freshwater discharge forms the large freshened surface layer (FSL) in the Kara Sea which is among the largest freshwater reservoirs in the Arctic Ocean (Aagaard & Carmack, 1989; Haine et al., 2015; Williams & Carmack, 2015) and governs many local physical, biological, and geochemical processes (Asadulin et al., 2013, 2015; Dubinina et al., 2017a, 2017b; Galimov et al., 2006; Gebhardt et al., 2004; Kohler et al., 2003; Levitan et al., 2005; Makkaveev et al., 2015; Miroshnikov, 2013; Mosharov et al., 2018a, 2018b; Osadchiev et al., 2017, 2020; Polukhin, 2019; Romanova & Boltenkova, 2020; Unger et al., 2005). Many previous studies addressed water masses, inflow of warmer water from the Barents Sea, and circulation in the Kara Sea (Dmitrenko et al., 2015; Harms & Karcher, 1999, 2005; McClimans et al., 2000; Morozov et al., 2003, 2008; Osadchiev et al., 2020b; Panteleev et al., 2007; Pavov & Pfirman, 1995; Zatsepin, et al., 2010a).…”
Section: Introductionmentioning
confidence: 99%
“…and governs many local physical, biological, and geochemical processes (Asadulin et al, 2013(Asadulin et al, , 2015Dubinina et al, 2017aDubinina et al, , 2017bGalimov et al, 2006;Gebhardt et al, 2004;Kohler et al, 2003;Levitan et al, 2005;Makkaveev et al, 2015;Miroshnikov, 2013;Mosharov et al, 2018aMosharov et al, , 2018bOsadchiev et al, 2017Osadchiev et al, , 2020Polukhin, 2019;Romanova & Boltenkova, 2020;Unger et al, 2005). Many previous studies addressed water masses, inflow of warmer water from the Barents Sea, and circulation in the Kara Sea (Dmitrenko et al, 2015;Harms & Karcher, 1999, 2005McClimans et al, 2000;Morozov et al, 2003Morozov et al, , 2008Osadchiev et al, 2020b;Panteleev et al, 2007;Pavov & Pfirman, 1995;Zatsepin, et al, 2010a).…”
The Kara Sea is a semi-enclosed sea located between the Siberian coast in the south, Novaya Zemlya in the west, and Severnaya Zemlya in the east (Figure 1). The water depth is less than 50 m at more than 40% of the Kara Sea; shallow areas are located mainly in the central and southeastern parts of the sea. This sea receives enormous freshwater discharge (∼1,500 km 3 annually) mainly from two large estuaries, namely, the Yenisei Gulf (630 km 3 from the Yenisei River) and the Gulf of Ob (530 km 3 from the Ob, Pur, and Taz rivers; Gordeev et al., 1996; Pavlov et al., 1996). Continental discharge to the Kara Sea has very large seasonal variability with a short freshet period in June-July that provides ∼50% of annual runoff and a long low discharge period in October-April caused by freezing of the inflowing rivers (Pavlov et al., 1996; Figure 1). Freshwater discharge forms the large freshened surface layer (FSL) in the Kara Sea which is among the largest freshwater reservoirs in the Arctic Ocean
“…The river flow slows down in this part of the bay, and seawater inflow is possible [49]. Sediments are commonly represented by homogenous silts and clays replaced by silty sands in marine parts [53] and consist mainly of terrestrial material transported as suspended matter. Sedimentation rates within the boundaries of the Ob-Yenisey shallow water can be as high as 1 cm per year [54].…”
The Siberian Arctic Shelf is an area of increasing anthropogenic activity and is predicted to be significantly impacted by climate change. Accordingly, there is an increased demand for baseline knowledge on the scales of natural spatiotemporal variation of different ecosystem components. The study aimed to investigate the spatial variability of macrobenthic communities and associated abiotic forcing in the Ob Bay, a major Arctic estuary. Four main zones of macrobenthic communities were identified: a brackish-water zone in the upper part of the estuary, which was divided into two subzones according to the dominant species; a transition zone at the mouth of the Ob Bay; and a marine zone. This zonation remained stable during the study period (2013–2019) and corresponded well with previous studies in the area. The large-scale variation in macrobenthic communities was related mainly to two independent drivers: salinity and sediment type. The within-zone variation increased with the number of coexisting species, but no temporal trends could be assessed. The study highlights the need to account for the small-scale heterogeneity of benthic communities to understand ecosystem functioning and long-term dynamics, particularly in areas where environmental conditions vary markedly.
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