Sediment transport to the Laptev Sea–hydrology and geochemistry of the Lena River

Rachold, Volker; Alabyan, A. M.; Hubberten, Hans-W.; Korotaev, V. N.; Zaitsev, A. A.

doi:10.3402/polar.v15i2.6646

Cited by 18 publications

(11 citation statements)

References 14 publications

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“…As seen in earlier studies, flocculation during estuarine mixing did not fractionate the Fe-isotopic composition of the colloids and particles (Bergquist and Boyle, 2006;Escoube et al, 2009;Fantle and DePaolo, 2004;Poitrasson et al, 2014). Other processes, such as resuspension of sediment and non-reductive dissolution of sediment to the seawater (Radic et al, 2011), would lead to a much more negative (−3.3 ‰ to −1.7 ‰) Fe-isotope composition of the sediment (Homoky et al, 2009;Severmann et al, 2006Severmann et al, , 2010. Therefore, the δ 56 Fe of the uppermost sediment reflecting the δ 56 Fe of the sedimenting colloids and particles from the water column seems reasonable.…”

Section: Iron Isotopes In the Lena River Freshwater Plumementioning

confidence: 49%

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

et al. 2019

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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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Section: Iron Isotopes In the Lena River Freshwater Plumementioning

confidence: 49%

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

et al. 2019

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“…The main sources of total suspended matter (TSM) are eroded land and the thawing permafrost (Rachold et al, 1996;Lobbes et al, 2000). Similar studies in the Kara Sea about optical properties, remote sensing, and carbon content were carried out by Pozdnyakov et al (2005), Hessen et al (2010), and Korosov et al (2011).…”

Section: Introductionmentioning

confidence: 86%

Contribution to a bio-optical model for remote sensing of Lena River water

et al. 2013

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Abstract. Bio-optical measurements and sampling were carried out in the delta of the Lena River (northern Siberia, Russia) between 26 June and 4 July 2011. The aim of this study was to determine the inherent optical properties of the Lena water, i.e., absorption, attenuation, and scattering coefficients, during the period of maximum runoff. This aimed to contribute to the development of a biooptical model for use as the basis for optical remote sensing of coastal water of the Arctic. In this context the absorption by CDOM (colored dissolved organic matter) and particles, and the concentrations of total suspended matter, phytoplankton-pigments, and carbon were measured. CDOM was found to be the most dominant parameter affecting the optical properties of the river, with an absorption coefficient of 4.5-5 m −1 at 442 nm, which was almost four times higher than total particle absorption values at visible wavelength range. The wavelenght-dependence of absorption of the different water constituents was chracterized by determining the semi logarithmic spectral slope. Mean CDOM, and detritus slopes were 0.0149 nm −1 (standard deviation (stdev) = 0.0003, n = 18), and 0.0057 nm −1 (stdev = 0.0017, n = 19), respectively, values which are typical for water bodies with high concentrations of dissolved and particulate carbon. Mean chlorophyll a and total suspended matter were 1.8 mg m −3 (stdev = 0.734 n = 18) and 31.9 g m −3 (stdev = 19.94, n = 27), respectively. DOC (dissolved organic carbon) was in the range 8-10 g m −3 and the total particulate carbon (PC) in the range 0.25-1.5 g m −3 . The light penetration depth (Secchi disc depth) was in the range 30-90 cm and was highly correlated with the suspended matter concentration. The period of maximum river runoff in June was chosen to obtain bio-optical data when maximum water constituents are transported into the Laptev Sea. However, we are aware that more data from other seasons and other years need to be collected to establish a general bio-optical model of the Lena water and conclusively characterize the light climate with respect to primary production.

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“…It is followed by the Bykovskaya branch with 25% towards southeast, by the Tumatskaya branch to the north and the Olenyokskaya branch to the west, each of them with 7% . During the last two decades several studies have been conducted on geomorphology (Korotaev, 1986;Grigoriev, 1993), cryolithology (Kunitsky, 1989), hydrology Rachold et al, 1996), paleogeography (Fukuda, 1994;Galabala, 1997;Are and Reimnitz, 2000), tectonics (Avetisov, 1999;Franke et al, 2000) and coastal retreat in the Lena Delta area. However, the sedimentation history as well as the processes that control the lateral extension of the Lena Delta in total are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Late Quaternary sedimentation history of the Lena Delta

Schwamborn

Rachold

Grigoriev

2002

Quaternary International

164

176

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Core and outcrop analysis from Lena mouth deposits have been used to reconstruct the Late Quaternary sedimentation history of the Lena Delta. Sediment properties (heavy mineral composition, grain size characteristics, organic carbon content) and age determinations ( 14 C AMS and IR-OSL) are applied to discriminate the main sedimentary units of the three major geomorphic terraces, which form the delta. The development of the terraces is controlled by complex interactions among the following four factors: (1) Channel migration. According to the distribution of 14 C and IR-OSL age determinations of Lena mouth sediments, the major river runoff direction shifted from the west during marine isotope stages 5-3 (third terrace deposits) towards the northwest during marine isotope stage 2 and transition to stage 1 (second terrace), to the northeast and east during the Holocene (first terrace deposits). (2) Eustasy. Sea level rise from Last Glacial lowstand to the modern sea level position, reached at 6-5 ka BP, resulted in back-filling and flooding of the palaeovalleys. (3) Neotectonics. The extension of the Arctic Mid-Ocean Ridge into the Laptev Sea shelf acted as a halfgraben, showing dilatation movements with different subsidence rates. From the continent side, differential neotectonics with uplift and transpression in the Siberian coast ridges are active. Both likely have influenced river behavior by providing sites for preservation, with uplift, in particular, allowing accumulation of deposits in the second terrace in the western sector. The actual delta setting comprises only the eastern sector of the Lena Delta. (4) Peat formation. Polygenetic formation of icerich peaty sand (''Ice Complex'') was most extensive (7-11 m in thickness) in the southern part of the delta area between 43 and 14 ka BP (third terrace deposits). In recent times, alluvial peat (5-6 m in thickness) is accumulated on top of the deltaic sequences in the eastern sector (first terrace). r

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Sediment transport to the Laptev Sea–hydrology and geochemistry of the Lena River

Cited by 18 publications

References 14 publications

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

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

Contribution to a bio-optical model for remote sensing of Lena River water

Late Quaternary sedimentation history of the Lena Delta

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