Freshwater transport between the Kara, Laptev, and East-Siberian seas

Abstract

The Kara and Laptev seas receive about one half of total freshwater runoff to the Arctic Ocean from the ob, Yenisei, and Lena rivers. Discharges of these large rivers form freshened surface water masses over wide areas in these seas. these water masses, i.e., the ob-Yenisei and Lena river plumes, generate an eastward buoyancy boundary current that accounts for the large-scale zonal freshwater transport along the Siberian part in the Arctic ocean. in this study we investigate spreading of the ob-Yenisei plume from the Kara Sea to the Laptev Sea through the Vilkitsky Strait and of the Lena plume from the Laptev Sea to the east-Siberian Sea through the Laptev and Sannikov straits during ice-free season. Large horizontal density gradient between freshened plume water and salty ambient sea water is the main driver of these processes, however, their intensity strongly depends on local wind forcing. the ob-Yenisei plume is spreading to the Laptev Sea in a narrow alongshore current which is induced by strong and long-term southwesterly winds. Under other wind forcing the plume does not reach the Vilkitsky Strait. the Lena plume is almost constantly spreading to the east-Siberian Sea as a large-scale surface water mass which intensity is governed by eastward ekman transport and is prone to large synoptic variability. The Ob, Yenisei and Lena rivers contribute large volumes of freshwater discharge into the Kara (~ 1,500 km 3 annually from the Ob and Yenisei rivers) and Laptev (~ 800 km 3 annually from the Lena River) seas that account for approximately one half of the total river runoff into the Arctic Ocean 1-3. Most of the continental runoff to the Kara and Laptev seas is discharged during ice-free period in June-September and forms sea-wide Ob-Yenisei and Lena river plumes which are among the largest freshwater reservoirs in the Arctic Ocean 4-6. River plumes are freshened surface-advected water masses, which seasonally form a relatively thin surface layer, compared to ambient saline sea. As a result, dynamics of river plumes is buoyancy-driven and wind-driven 7-12 , which is also true for large Ob-Yenisei and Lena plumes 3,13-18. It was previously investigated, that in the absence of strong wind forcing the Coriolis force and large salinity gradient between river plumes and ambient shelf water induce a baroclinic flow along the coast, which was previously addressed in many studies 7,19-21. This flow can be favored or impeded by local wind forcing. The associated eastward freshwater transport along large segments of northern shores of Eurasia and North America is an important part of large-scale freshwater transport pathways in the Arctic Ocean 22-27. Eastward alongshore spreading of the Ob-Yenisei and Lena plumes as a buoyancy-driven boundary current was described as a part of the Siberian Coastal Current (SCC) 22 which is the Eurasian branch of the Riverine Coastal Domain (RCD) 26. However, only few previous studies specifically addressed spreading of these river plumes from their source sea to an eastward sea, i.e., ...

Insights Into Water Mass Origins in the Central Arctic Ocean From In‐Situ Dissolved Organic Matter Fluorescence

“…A branch of the Barents Sea supply of AW contains a contribution from the Norwegian Coastal Current and flows along the Siberian shelf and slope (Osadchiev et al., 2020; Rudels et al., 2004). During this passage it collects freshwater (Bauch et al., 2014) and DOM from Siberian rivers (Kaiser et al., 2017).…”

Using Remotely Sensed Sea Surface Salinity and Colored Detrital Matter to Characterize Freshened Surface Layers in the Kara and Laptev Seas during the Ice-Free Season

“…In the Kara and Laptev seas, there is an eastward freshwater transport that spreads surface-advected river plumes from the Kara to the Laptev through the Vilkitsky Strait, and from the Laptev to the East-Siberian seas through the Laptev and Sannikov straits. The effect of eastward transport [61] can be seen in satellite images (Figures A1 and A2). Except for the year 2015, where fresh and highly absorbing waters extended further northward than in the rest of the study period (2011-2019), waters typically had higher CDM and lower SSS eastward of the river mouth than northward.…”

“…We considered the FSL depth to be constant, based on previous references: 12 m for the Kara Sea [61] and 10 m for the Laptev Sea [59,60].…”

“…Except for the year 2015, where fresh and highly absorbing waters extended further northward than in the rest of the study period (2011-2019), waters typically had higher CDM and lower SSS eastward of the river mouth than northward. This can be explained as follows: (i) The eastward transport is wind-driven and characterized by a quick response to synoptic variability of wind forcing [57,61]. Therefore, waters reaching east had less time to experience removal processes; (ii) it could also be related to the contributions of smaller tributaries along the coastline; or (iii) the erosion of permafrost coasts that release CDM into the coastal seas.…”

Distribution and Transport of Water Masses in the East Siberian Sea and Their Impacts on the Arctic Halocline

“…The positive buoyancy input provided by river discharge drives an eastward‐flowing low‐salinity current called the Siberian Coastal Current (Chapman & Lentz, 1994; Münchow et al., 1999). The direction and along‐coast extent of the coastal current are also influenced by surface wind stress, which determines the freshwater transport along the continental shelf of Russia (Osadchiev et al., 2020; Savel'eva et al., 2008; Weingartner et al., 1999).…”