Internal Waves as a Source of Concentric Rings within Small River Plumes

Osadchiev, Alexander; Sedakov, Roman; Gordey, Alexandra; Barymova, Alexandra

doi:10.3390/rs13214275

Cited by 4 publications

(4 citation statements)

References 12 publications

(27 reference statements)

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“…For this purpose, we performed five field surveys at the small Kodor and Bzyp river plumes located at the eastern part of the Black Sea in 2018-2022. This study continues our previous research of small river plumes in the Black Sea focused on the structure of small plumes [2,3,57], influence of wind forcing and river discharge variability on small plumes [4,58,59], generation of internal waves in river plumes [6,60], influence of small plumes on water quality and marine pollution [14,61].…”

Section: Discussionsupporting

confidence: 78%

“…Five field surveys described in this study were performed at the buoyant plumes formed by the Kodor and Bzyb rivers in the eastern part of the Black Sea (Figure 1). General characteristics of the Kodor and Bzyb plumes and the ambient saline sea are described in detail by Osadchiev et al [2][3][4]6]. The information about all field surveys analyzed in the study is summarized in georeferenced by direct projection into an earth-based Cartesian coordinate system using GPS and altimetry data from the quadcopter.…”

Section: Aerial Observations and In Situ Measurementsmentioning

confidence: 99%

“…These gradients are especially strong at plumes formed by small rivers, which have small spatial scales and small freshwater residence time equal to hours and days [1][2][3]. In particular, horizontal (3-4 salinity units/m [2,4]) and vertical (5-6 salinity units/m [5,6]) salinity gradients observed at the outer borders of small plumes are among the largest reported in the World Ocean.…”

Section: Introductionmentioning

confidence: 95%

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Lateral Border of a Small River Plume: Salinity Structure, Instabilities and Mass Transport

et al. 2022

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The interfaces between small river plumes and ambient seawater have extremely sharp horizontal and vertical salinity gradients, often accompanied by velocity shear. It results in formation of instabilities at the lateral borders of small plumes. In this study, we use high-resolution aerial remote sensing supported by in situ measurements to study these instabilities. We describe their spatial and temporal characteristics and then reconstruct their relation to density gradient and velocity shear. We report that Rayleigh–Taylor instabilities, with spatial scales ~5–50 m, are common features of the sharp plume-sea interfaces and their sizes are proportional to the Atwood number determined by the cross-shore density gradient. Kelvin–Helmholtz instabilities have a smaller size (~3–7 m) and are formed at the plume border in case of velocity shear >20–30 cm/s. Both instabilities induce mass transport across the plume-sea interfaces, which modifies salinity structure of the plume borders and induces lateral mixing of small river plumes. In addition, aerial observations revealed wind-driven Stokes transport across the sharp plume-sea interface, which occurs in the shallow (~2–3 cm) surface layer. This process limitedly affects salinity structure and mixing at the plume border, however, it could be an important issue for the spread of river-borne floating particles in the ocean.

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Section: Discussionsupporting

confidence: 78%

Section: Aerial Observations and In Situ Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

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Lateral Border of a Small River Plume: Salinity Structure, Instabilities and Mass Transport

et al. 2022

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“…Previous research revealed significant seasonal variability of both characteristics of the Ob-Yenisei plume during ice-free season [8,35]. In June-July, during the peak river discharge, the Ob-Yenisei plume is low-saline (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) and relatively shallow (10 m). Then, in August-October salinity of the plume steadily increases to 15-25, its depth also increases to 10-15 m. Total freshwater volume contained in the Ob-Yenisei plume accumulates during the ice-free season from ~600 km 3 in June-July to ~900 km 3 in October.…”

Section: Vertical Salinity Structure and Adtmentioning

confidence: 97%

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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Response of a Small River Plume on Wind Forcing

2021

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Wind forcing is the main driver of river plume dynamics. Direction and magnitude of wind determine position, shape, and size of a river plume. The response of river plumes on wind forcing was simulated in many numerical modeling studies; however, in situ measurements of this process are still very scarce. In this study, we report the first direct measurements of frontal movement of a small river plume under variable wind forcing conditions. Using quadcopters, we performed nearly continuous daytime aerial observations of the Bzyb river plume located in the non-tidal Black Sea. The aerial remote sensing was accompanied by synchronous in situ measurements of wind forcing. We assessed spreading patterns of the plume and evaluated movement velocity of its outer border with unprecedentedly high spatial (∼10 m) and temporal (∼1 min) resolution, which was not available in previous studies based on in situ measurements and satellite observations. Based on the collected data, we evaluated the time of response of plume spreading dynamics on changes in wind forcing conditions. The advection velocity of the outer plume border shows linear relation to wind speed with very small response time (10–20 min). The reversal between upstream/downstream plume spreading occurs during several hours under moderate wind forcing conditions. These reversals involve only near-field part of the plume, which cause detachment of the far-field part of the plume. The obtained results are crucial for understanding and simulating spreading dynamics of small river plumes worldwide.

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Internal Waves as a Source of Concentric Rings within Small River Plumes

Cited by 4 publications

References 12 publications

Lateral Border of a Small River Plume: Salinity Structure, Instabilities and Mass Transport

Lateral Border of a Small River Plume: Salinity Structure, Instabilities and Mass Transport

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

Response of a Small River Plume on Wind Forcing

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