scholarly journals Numerical estimations of desalinated seawater modification using Laptev sea shelf seawater as the example

2019 ◽  
Vol 484 (3) ◽  
pp. 352-357
Author(s):  
Е. О. Dubinina ◽  
А. Yu. Miroshnikov ◽  
S. А. Kossova ◽  
M. V. Flint
Keyword(s):  
Fresh Water ◽  
Laptev Sea ◽  
Lena River ◽  
New Model ◽  
River Input ◽  
Modification Process ◽  
Fresh Water Input ◽  
The Laptev Sea ◽  
Numerical Estimations

A new model for describing the behavior of the isotope (d18О, dD) parameters of desalinated seawater during freezing is proposed. The model was tested using the Laptev Sea shelf waters, which are actively desalinated by the Lena river input and modified by the freezing and ice removing. It is shown that taking into account the modification process leads to the correction of estimates of the fraction of fresh water input up to 20%. A criterion for determination of model availability is proposed.

Features of the Lena River runoff influence on the adjacent Laptev Sea shelf

2021 ◽  
Author(s):  
Vladimir Rogozhin ◽  
Alexander Polukhin ◽  
Evgeniy Yakushev ◽  
Igor Semiletov
Keyword(s):  
Fresh Water ◽  
River Runoff ◽  
Total Alkalinity ◽  
Shelf Zone ◽  
Laptev Sea ◽  
Shirshov Institute ◽  
Riverine Water ◽  
Lena River ◽  
The Laptev Sea ◽  
Lena Delta

<p>The annual runoff of river water into the Laptev Sea is 745 km<sup>3</sup>, most of the runoff belongs to the Lena River - 525 km<sup>3</sup>.  Long-term variability in the volume of the Lena River runoff play a significant role in the variability of the scale of distribution of freshwater lenses in the Laptev Sea. The processes that take place in the area of ​​intense river runoff have an impact both in the shelf zone and in the open part of the sea due to the transfer of large-area lenses of freshened water. The influence of river runoff is considered from the Lena Delta to the continental slope of the Laptev Sea.</p><p>The data on physical and chemical properties of the Laptev Sea shelf used in this investigation was obtained during the expeditions of the Shirshov Institute of Oceanology in 2015 and 2017 and the Pacific Oceanological Institute in 2018-2020.</p><p>The distribution of hydrochemical parameters in the Lena Delta area in 2019 was typical for the river-sea mixing zone. The distribution of silicate was mixed, i.e. horizontal stratification prevailed in the near-surface layers, and vertical stratification in the bottom layers. The maximum values ​​were observed in the near-mouth area, reaching indicators over 30 µM / L, which generally coincides with the values ​​of this indicator in 2015 and more than in 2017.</p><p>When considering the distribution of specific alkalinity (total alkalinity-salinity ratio), which serves as a proxie of riverine water, it is worth noting the deepening of the boundary by 0.07 units. In 2019, this border was at depths of 20 to 40 meters, which is an atypical indicator for this water area. Apparently, this has happened owing to an increase in the supply of carbonate ions, which is noticeable from an increase in the values ​​of carbonate alkalinity in the Lena River waters (Arctic Great Rivers Observatory data).</p><p>The calculation of the parts of fresh water, based on salinity data in 2019, showed that the maximum values ​​were observed near the Lena River delta and amounted to 30-35%. Northward, the part of riverine water was up to 10% only in the surface layer. Comparing with similar calculations performed for the 2015 and 2017 sections, it should be noted that the part of fresh water has decreased. Perhaps this is due to the inflow of continental runoff in 2019 was the lowest over the considered period.</p><p>Funding: The work was carried out within the framework of the Shirshov Institute of Oceanology state assignment (theme No. 0149-2019-0008), with funding of the Russian Scientific Foundation (project No. 19-17-00196) and the grant of the President of the Russian Federation MK-860.2020.5.</p>

scholarly journals Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3511
Author(s):  
Elena Gershelis ◽  
Andrey Grinko ◽  
Irina Oberemok ◽  
Elizaveta Klevantseva ◽  
Natalina Poltavskaya ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Sediments ◽  
Continental Margins ◽  
Laptev Sea ◽  
Lena River ◽  
Nearshore Sediments ◽  
Rock Eval ◽  
Molecular Indicators ◽  
Sedimentation Regime ◽  
The Laptev Sea

Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper.

scholarly journals On the biogeochemical signature of the Lena River from its headwaters to the Arctic Ocean

2011 ◽  
Vol 8 (2) ◽  
pp. 2093-2143 ◽  
Author(s):  
I. P. Semiletov ◽  
I. I. Pipko ◽  
N. E. Shakhova ◽  
O. V. Dudarev ◽  
S. P. Pugach ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Arctic Ocean ◽  
River Discharge ◽  
Total Carbon ◽  
The Arctic ◽  
Time Shift ◽  
Laptev Sea ◽  
Lena River ◽  
The Arctic Ocean ◽  
The Laptev Sea

Abstract. The Lena River integrates biogeochemical signals from its vast drainage basin and its signal reaches far out over the Arctic Ocean. Transformation of riverine organic carbon into mineral carbon, and mineral carbon into the organic form in the Lena River watershed, can be considered a quasi-equilibrated processes. Increasing the Lena discharge causes opposite effects on total organic (TOC) and inorganic (TCO2) carbon: TOC concentration increases, while TCO2 concentration decreases. Significant inter-annual variability in mean values of TCO2, TOC, and their sum (TC) has been found. This variability is determined by changes in land hydrology which cause differences in the Lena River discharge, because a negative correlation may be found between TC in September and mean discharge in August (a time shift of about one month is required for water to travel from Yakutsk to the Laptev Sea). Total carbon entering the sea with the Lena discharge is estimated to be almost 10 Tg C y−1. The annual Lena River discharge of particulate organic carbon (POC) may be equal to 0.38 Tg (moderate to high estimate). If we instead accept Lisytsin's (1994) statement concerning the precipitation of 85–95% of total particulate matter (PM) (and POC) on the marginal "filter", then only about 0.03–0.04 Tg of POC reaches the Laptev Sea from the Lena River. The Lena's POC export would then be two orders of magnitude less than the annual input of eroded terrestrial carbon onto the shelf of the Laptev and East Siberian seas, which is about 4 Tg. The Lena River is characterized by relatively high concentrations of primary greenhouse gases: CO2 and dissolved CH4. During all seasons the river is supersaturated in CO2 compared to the atmosphere: up to 1.5–2 fold in summer, and 4–5 fold in winter. This results in a narrow zone of significant CO2 supersaturation in the adjacent coastal sea. Spots of dissolved CH4 in the Lena delta channels may reach 100 nM, but the CH4 concentration decreases to 5–20 nM towards the sea, which suggests only a minor role of riverborne export of CH4 for the East Siberian Arctic Shelf (ESAS) CH4 budget in coastal waters. Instead, the seabed appears to be the source that provides most of the CH4 to the Arctic Ocean.

Numerical Estimations of Desalinated Seawater Modification Using Waters of the Laptev Sea Shelf as an Example

2019 ◽  
Vol 484 (1) ◽  
pp. 109-113
Author(s):  
E. O. Dubinina ◽  
A. Yu. Miroshnikov ◽  
S. A. Kossova ◽  
M. V. Flint
Keyword(s):  
Laptev Sea ◽  
The Laptev Sea ◽  
Numerical Estimations

scholarly journals Bioindication of the water salinity dynamics by the microalgae communities in the Lena River Delta, Laptev Sea, Russian Arctic

2021 ◽  
Vol 6 (3) ◽  
pp. 15-28
Author(s):  
S. S. Barinova ◽  
V. A. Gabyshev ◽  
A. P. Ivanova ◽  
O. I. Gabysheva
Keyword(s):  
Species Composition ◽  
River Delta ◽  
Water Bodies ◽  
Water Salinity ◽  
The Arctic ◽  
Laptev Sea ◽  
Russian Arctic ◽  
Lena River ◽  
Lena River Delta ◽  
The Laptev Sea

The Lena River in the Laptev Sea forms a vast delta, one of the largest in the world. The Ust-Lensky State Nature Reserve saves biodiversity on the Lena Delta territory beyond the Arctic Circle, in the zone of continuous permafrost. In recent years, large-scale plans for the development of extractive industries are implemented in this Russian Arctic sector. In this regard, the study of biodiversity and bioindication properties of aquatic organisms in the Lena River estuary area is becoming more and more relevant. This study aims to identify the species composition of microalgae in lotic and lentic water bodies of the Lena River Delta and use their indicator property for water salinity. It was a trace indicator of species distribution over the delta and their dynamics along the delta main watercourses to assess the impact of river waters on the Laptev Sea coastal areas. For this, all previously published materials on algae and chemical composition of the region waters as well as data obtained in recent years for the waters of the lower Lena reach were involved. In total, 700 species considered to 10 phyla were analyzed: Cyanobacteria (83), Euglenozoa (13), Ochrophyta (Chrysophyta, Xanthophyta) (41), Eustigmatophyta (4), Bacillariophyta (297), Miozoa (20), Cryptophyta (3), Rhodophyta (1), Chlorophyta (125), and Charophyta (111). The available materials of the field and reference observations were analyzed using several statistical methods. The study results indicate that hydrological conditions are the main factor regulating the spatial structure of the species composition of the microalgae communities in the Lena River Delta. The distribution of groups of salinity indicators across flowing water bodies reflects the effect of water salinity, and this allows suggesting possible sources of this effect. The mechanism of tracking the distribution of environmental indicators itself is a sensitive method, that reveals even their subtle changes in them; therefore, as an integral method, it can be helpful for further monitoring.

Mercury and methylmercury along a transect from the Lena river estuary across the Laptev Sea Shelf

2020 ◽  
Author(s):  
Van Liem Nguyen ◽  
Birgit Wild ◽  
Örjan Gustafsson ◽  
Igor Semiletov ◽  
Oleg Dudarev ◽  
...  
Keyword(s):  
Organic Matter ◽  
Continental Shelf ◽  
Arctic Ocean ◽  
River Delta ◽  
The Arctic ◽  
Laptev Sea ◽  
Terrestrial Organic Matter ◽  
Lena River ◽  
The Arctic Ocean ◽  
The Laptev Sea

<p>Widespread accelerated permafrost thawing is predicted for this century and beyond. This threatens to remobilize the large amounts of Mercury (Hg) currently ‘locked’ in Arctic permafrost soils to the Arctic Ocean and thus potentially lead to severe consequences for human and wildlife health. Future risks of Arctic Hg in a warmer climate are, however, poorly understood. One crucial knowledge gap to fill is the fate of Hg once it enters the marine environment on the continental shelves. Arctic rivers are already today suggested to be the main source of Hg into the Arctic Ocean, with dissolved and particulate organic matter (DOM and POM, respectively) identified as important vectors for the land to sea transport.</p><p>In this study, we have investigated total Hg (HgT) and monomethylmercury (MeHg) concentrations in surface sediments from the East Siberian Arctic Shelf (ESAS) along a transect from the Lena river delta to the Laptev Sea continental slope. The ESAS is the world’s largest continental shelf and receives large amounts of organic carbon by the great Arctic Russian rivers (e.g., Lena, Indigirka and Kolyma), remobilized from continuous and discontinuous permafrost regions in the river catchments, and from coastal erosion. Data on HgT and MeHg levels in ESAS sediments is however limited. Here, we observed concentrations of Hg ranging from 30 to 96 ng Hg g<sup>-1</sup> d.w. of HgT, and 0.03 to 9.5 ng Hg g<sup>-1</sup> d.w. of MeHg. Similar concentrations of HgT were observed close to the river delta (54 ± 19 ng Hg g<sup>-1</sup> d.w.), where >95 % of the organic matter is of terrestrial origin, and the other section of the transect (42 ± 7 ng Hg g<sup>-1</sup> d.w.) where the terrestrial organic matter is diluted with carbon from marine sources. In contrast, we observed higher concentrations of MeHg close to the river delta (0.72 ± 0.71 ng Hg g<sup>-1</sup> d.w. as MeHg) than further out on the continental shelf (0.031 ± 0.71 ng Hg g<sup>-1</sup> d.w. as MeHg). We also observed a positive correlation between the MeHg:Hg ratio and previously characterized molecular markers of terrestrial organic matter (Bröder et al. Biogeosciences (2016) & Nature Com. (2018)). We thus suggest riverine inputs, rather than in situ MeHg formation, to explain observed MeHg trends.</p>

scholarly journals A multiproxy-based reconstruction of the mid- to late Holocene paleoenvironment in the Laptev Sea off the Lena River Delta (Siberian Arctic)

2020 ◽  
Vol 540 ◽  
pp. 109502
Author(s):  
Оlga Rudenko ◽  
Еkaterina Taldenkova ◽  
Yaroslav Ovsepyan ◽  
Аnna Stepanova ◽  
Henning A. Bauch
Keyword(s):  
Late Holocene ◽  
River Delta ◽  
Laptev Sea ◽  
Lena River ◽  
Siberian Arctic ◽  
Lena River Delta ◽  
The Laptev Sea

scholarly journals Distribution of Fe isotopes in particles and colloids in the salinity gradient along the Lena River plume, Laptev Sea

2019 ◽  
Vol 16 (6) ◽  
pp. 1305-1319 ◽  
Author(s):  
Sarah Conrad ◽  
Johan Ingri ◽  
Johan Gelting ◽  
Fredrik Nordblad ◽  
Emma Engström ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Salinity Gradient ◽  
River Mouth ◽  
The Arctic ◽  
Shelf Zone ◽  
Laptev Sea ◽  
Lena River ◽  
Freshwater Plume ◽  
The Laptev Sea ◽  
Particles And Colloids

Abstract. Riverine Fe input is the primary Fe source for the ocean. This study is focused on the distribution of Fe along the Lena River freshwater plume in the Laptev Sea using samples from a 600 km long transect in front of the Lena River mouth. Separation of the particulate (>0.22 µm), colloidal (0.22 µm–1 kDa), and truly dissolved (<1 kDa) fractions of Fe was carried out. The total Fe concentrations ranged from 0.2 to 57 µM with Fe dominantly as particulate Fe. The loss of >99 % of particulate Fe and about 90 % of the colloidal Fe was observed across the shelf, while the truly dissolved phase was almost constant across the Laptev Sea. Thus, the truly dissolved Fe could be an important source of bioavailable Fe for plankton in the central Arctic Ocean, together with the colloidal Fe. Fe-isotope analysis showed that the particulate phase and the sediment below the Lena River freshwater plume had negative δ56Fe values (relative to IRMM-14). The colloidal Fe phase showed negative δ56Fe values close to the river mouth (about −0.20 ‰) and positive δ56Fe values in the outermost stations (about +0.10 ‰). We suggest that the shelf zone acts as a sink for Fe particles and colloids with negative δ56Fe values, representing chemically reactive ferrihydrites. The positive δ56Fe values of the colloidal phase within the outer Lena River freshwater plume might represent Fe oxyhydroxides, which remain in the water column, and will be the predominant δ56Fe composition in the Arctic Ocean.

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