Properties of surface water masses in the Laptev and the East Siberian seas in summer 2018 from in situ and satellite data

Tarasenko, Anastasiia; Supply, Alexandre; Kusse-Tiuz, Nikita; Ivanov, Vladimir; Makhotin, Mikhail; Tournadre, Jean; Chapron, Bertrand; Boutin, Jacqueline; Kolodziejczyk, Nicolas; Reverdin, Gilles

doi:10.5194/os-17-221-2021

Cited by 21 publications

(31 citation statements)

References 60 publications

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“…Despite certain progress in deriving sea surface salinity from satellite measurements in the Arctic Ocean, these products demonstrate proper accuracy only for high salinity values (>28-30), while there is no evidence that they operate well at salinities <25, which are typical for FSL (Matsuoka et al, 2016;Olmedo et al, 2018;Tang et al, 2018;Supply et al, 2020). In particular, satellite-derived sea surface salinity at the study area analyzed recently by Tarasenko et al (2021) was not properly validated against in situ salinity data for low-saline shelf areas. As a result, the presented satellitederived salinity distributions did not reproduce sharp salinity gradients typical for the outer border of FSL.…”

Section: Introductionmentioning

confidence: 90%

Structure and Inter-Annual Variability of the Freshened Surface Layer in the Laptev and East-Siberian Seas During Ice-Free Periods

et al. 2021

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This work is focused on the structure and inter-annual variability of the freshened surface layer (FSL) in the Laptev and East-Siberian seas during ice-free periods. This layer is formed mainly by deltaic rivers among which the Lena River contributes about two thirds of the inflowing freshwater volume. Based on in situ measurements, we show that the area of this FSL during certain years is much greater than the area of FSL in the neighboring Kara Sea, while the total annual freshwater discharge to the Laptev and East-Siberian seas is 1.5 times less than to the Kara Sea (mainly from the estuaries of the Ob and Yenisei rivers). This feature is caused by differences in morphology of the estuaries and deltas. Shallow and narrow channels of the Lena Delta are limitedly affected by sea water. As a result, undiluted Lena discharge inflows to sea from multiple channels and forms relatively shallow plume, as compared to the Ob-Yenisei plume, which mixes with subjacent saline sea water in deep and wide estuaries. Due to small vertical extents of FSL in the Laptev and East-Siberian seas, wind conditions strongly affect its spreading and determine its significant inter-annual variability, as compared to relatively stable FSL in the Kara Sea. During years with prevailing western and northern winds, FSL is localized in the southern parts of the Laptev and East-Siberian seas due to southward Ekman transport, meridional extent (<250 km) and area (∼250,000 km2) of FSL are relatively small. During years with strong eastern winds FSL spreads northward over large area (up to 500,000 km2), its meridional extent increases up to 500–700 km. At the same time, area and position of FSL do not show any dependence on significant variability of the annual river discharge volume and ice coverage during warm season.

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Section: Introductionmentioning

confidence: 90%

Structure and Inter-Annual Variability of the Freshened Surface Layer in the Laptev and East-Siberian Seas During Ice-Free Periods

et al. 2021

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“…Despite seasonal changes in the plume structure, strong wind forcing also could substantially affect sea level and break the ADT-salinity correlation on a synoptic time scale. Strong and durable winds induce wind surges at the coastal areas, which is the case of the Kara Sea [32,[52][53][54]. The threshold value of wind speed, which causes change of sea level by more than 10 cm in the study area (i.e., comparable with plume-sea ADT difference) is equal to 6-8 m/s [32,55].…”

Section: Wind Forcing and Adtmentioning

confidence: 89%

“…However, further we analyze the causes of this feature and describe conditions, when ADT is indicative of satellite salinity and could be used for detection of the Ob-Yenisei plume. Surface salinity and ADT have certain negative correlation, namely, ADT at low salinities (0-20) is equal to 0-25 cm, which is greater than ADT at high salinities (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) equal to −20-20 cm. However, the observed variability of ADT within individual salinity values is very large.…”

Section: Surface Salinity Structure and Adtmentioning

confidence: 98%

“…Satellite altimetry has potential to be an important tool for studying these large river plumes especially because their outer areas are blurred and not well detected at thermal and optical satellite imagery [25] (which is not the case of small river plumes with sharp thermal and optical gradients at the borders with saline sea [26,27]). However, we are aware only of several works, which apply (albeit limitedly and in combination with other satellite products) satellite altimetry for studying large river plumes [28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

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Large River Plumes Detection by Satellite Altimetry: Case Study of the Ob–Yenisei Plume

Frey

Osadchiev

2021

Remote Sensing

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Satellite altimetry is an efficient instrument for detection dynamical processes in the World Ocean, including reconstruction of geostrophic currents and tracking of mesoscale eddies. Satellite altimetry has the potential to detect large river plumes, which have reduced salinity and, therefore, elevated surface level as compared to surrounding saline sea. In this study, we analyze applicability of satellite altimetry for detection of the Ob–Yenisei plume in the Kara Sea, which is among the largest river plumes in the World Ocean. Based on the extensive in situ data collected at the study area during oceanographic surveys in 2007–2019, we analyze the accuracy and efficiency of satellite altimetry in reproducing, first, the outer boundary of the plume and, second, the internal structure of the plume. We reveal that the value of positive level anomaly within the Ob–Yenisei plume strongly depends on the vertical plume structure and is prone to significant synoptic and seasonal variability due to wind forcing and mixing of the plume with subjacent sea. As a result, despite generally high statistical correlation between the ADT and surface salinity, straightforward usage of ADT for detection of the river plume is incorrect and produces misleading results. Satellite altimetry could provide correct information about spatial extents and shape of the Ob–Yenisei plume only if it is validated by synchronous in situ measurements.

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“…Local ice melt water should have a low CDM signature; therefore, this would allow us to distinguish between sea ice melt water and river water, as detailed in [73] where they used SSS and Ocean Color data to discriminate between water masses. However, the analysis of isotope characteristics of freshened surface layers in the Kara Sea has revealed that its volume is composed of river water directly mixed with saline water [40,[74][75][76]. During late summer and autumn, the large river discharge determines the freshwater balance, while the contribution of sea ice melt is negligible [48].…”

Section: Correlation Between Sea Surface Salinity and Colored Detrital Mattermentioning

confidence: 99%

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

et al. 2021

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The overall volume of freshwater entering the Arctic Ocean has been growing as glaciers melt and river runoff increases. Since 1980, a 20% increase in river runoff has been observed in the Arctic system. As the discharges of the Ob, Yenisei, and Lena rivers are an important source of freshwater in the Kara and Laptev Seas, an increase in river discharge might have a significant impact on the upper ocean circulation. The fresh river water mixes with ocean water and forms a large freshened surface layer (FSL), which carries high loads of dissolved organic matter and suspended matter into the Arctic Ocean. Optically active material (e.g., phytoplankton and detrital matter) are spread out into plumes, which are evident in satellite data. Russian river signatures in the Kara and Laptev Seas are also evident in recent SMOS Sea Surface Salinity (SSS) Arctic products. In this study, we compare the new Arctic+ SSS products, produced at the Barcelona Expert Center, with the Ocean Color absorption coefficient of colored detrital matter (CDM) in the Kara and Laptev Seas for the period 2011–2019. The SSS and CDM are found to be strongly negatively correlated in the regions of freshwater influence, with regression coefficients between −0.72 and −0.91 in the studied period. Exploiting this linear correlation, we estimate the SSS back to 1998 using two techniques: one assuming that the relationship between the CDM and SSS varies regionally in the river-influenced areas, and another assuming that it does not. We use the 22-year time-series of reconstructed SSS to estimate the interannual variability of the extension of the FSL in the Kara and Laptev Seas as well as their freshwater content. For the Kara and Laptev Seas, we use 32 and 28 psu as reference salinities, and 26 and 24 psu isohalines as FSL boundaries, respectively. The average FSL extension in the Kara Sea is 2089–2611 km2, with a typical freshwater content of 11.84–14.02 km3. The Laptev Sea has a slightly higher mean FSL extension of 2320–2686 km2 and a freshwater content of 10.15–12.44 km3. The yearly mean freshwater content and extension of the FSL, computed from SMOS SSS and Optical data, is (as expected) found to co-vary with in situ measurements of river discharge from the Arctic Great Rivers Observatory database, demonstrating the potential of SMOS SSS to better monitor the river discharge changes in Eurasia and to understand the Arctic freshwater system during the ice-free season.

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Properties of surface water masses in the Laptev and the East Siberian seas in summer 2018 from in situ and satellite data

Cited by 21 publications

References 60 publications

Structure and Inter-Annual Variability of the Freshened Surface Layer in the Laptev and East-Siberian Seas During Ice-Free Periods

Structure and Inter-Annual Variability of the Freshened Surface Layer in the Laptev and East-Siberian Seas During Ice-Free Periods

Large River Plumes Detection by Satellite Altimetry: Case Study of the Ob–Yenisei Plume

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

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