A two-layer model of the Rhine plume

Kok, J.M. de

doi:10.1016/0924-7963(96)00010-3

Cited by 23 publications

(10 citation statements)

References 25 publications

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“…The river flows through Lake Constance at the border of Germany, Austria, and Switzerland and meanders over a distance of 1,320 km before entering the southern North Sea through the ''Nieuwe Waterweg'' near Rotterdam and the sluices in the Haringvliet. With an average annual discharge of 2,300 m 3 s 21 (de Kok 1996), together with the Meuse in a mixed estuary, the Rhine is the most important river flowing into the southern North Sea. The Meuse rises in the Langre plateau in France before flowing through Belgium and the Netherlands.…”

Section: Methodsmentioning

confidence: 99%

“…The southern North Sea was selected as the main location for this work because of the large influence of West European and British rivers, its diverse hydrographical dynamics, and its generally low sedimentation rates. Because the Rhine/Meuse is the most important river system flowing into this area (de Kok 1996), water sampling was also carried out in these two rivers and their tributaries. In addition, because the branched GDGTs are presumably of soil and peat origin, measurements were also made in the surface water of a Swiss peat bog.…”

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confidence: 99%

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Characterization of transport and deposition of terrestrial organic matter in the southern North Sea using the BIT index

et al. 2006

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We have applied a recently introduced proxy, the BIT (branched and isoprenoid tetraether) index, to determine terrestrial organic matter (TOM) transport from the rivers Rhine and Meuse and their tributaries to the southern North Sea. This index is based on crenarchaeol, an isoprenoidal glycerol dialkyl glycerol tetraether (GDGT) predominantly derived from aquatic Crenarchaeota and branched GDGTs produced by soil bacteria. Up to 1.6 ng L 21 of branched GDGTs were measured in seawater, demonstrating the presence of TOM in the southern North Sea. BIT indices were inversely correlated with salinity, indicating that this TOM was recently supplied by rivers. The substantial amount of branched GDGTs (35 ng L 21 ) detected in river water and the high branched GDGT concentration measured in the water of a Swiss peat bog (5,900 ng L 21 ) suggest fluvial transport of branched GDGTs from peats and soils to the oceans. The high crenarchaeol concentration measured in river water (4.4 ng L 21 ) was probably derived from crenarchaeota living in rivers and organic material from soil and peat. The BIT index, d 13 C value, and C : N ratio of surface sediments deposited in the southern North Sea were compared to determine TOM deposition. BIT index (0.07 to 0.26) and d 13 C (220.6 to 222.9%) both showed substantial small-scale differences in TOM deposition in the southern North Sea, but this pattern was not obvious from the C : N ratios. A good correlation was found between d 13 C and branched GDGT concentrations, indicating that the absolute GDGT concentrations give additional information to the BIT index.Rivers provide large amounts of organic carbon to the marine environment (,4 3 10 14 g C yr 21 ; Schlesinger and Melack 1981) and are thus a key component of the global carbon cycle. Analysis of the terrestrial organic matter (TOM) buried in marine sediments is widely carried out to estimate the importance and fate of TOM in carbon cycling. In paleoenvironmental studies, determination of TOM transport can also provide useful information on, for example, the proximity of the continent, river fluxes, and wind strength. The distinction between organic carbon of marine and terrestrial origins is commonly made by analyzing the C : N ratio and the 13 C content of bulk organic matter (Meyers et al. 1994). Numerous biomarkers derived from higher plants are also used as proxies for tracing TOM input in marine sediments. However, several problems are inherent to both approaches (Hedges et al. 1997;Pancost and Boot 2004). For instance, the inconstancy of the d 13 C values of phytoplanktonic organic matter and TOM (e.g., C3 vs. C4 vegetation) renders the estimation of the proportion of terrestrial to marine organic matter in sediments difficult. Similarly, the difference in degradation rates of terrestrial-derived and marine-derived compounds may lead to erroneous estimation of terrestrial input in marine settings. These shortcomings make accurate quantification of TOM input in marine environments challenging (Hopmans et al. 2004, an...

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Characterization of transport and deposition of terrestrial organic matter in the southern North Sea using the BIT index

et al. 2006

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“…The Rhine, together with the Meuse in a mixed estuary, enters the southern North Sea through the Rotterdam Waterway (Nieuwe Waterweg) and the Haringvliet. With an average annual discharge of 2300 m 3 s À1 (de Kok, 1996), it is the most important river flowing into the southern North Sea.…”

Section: Study Areamentioning

confidence: 99%

“…As the Rhine/Meuse is the most important river system flowing into the area (de Kok, 1996), TEX 86 was also applied to suspended POM collected from the Rhine.…”

Section: Introductionmentioning

confidence: 99%

Application of the TEX86 temperature proxy to the southern North Sea

Herfort

Schouten

Boon

et al. 2006

Organic Geochemistry

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A novel temperature proxy, the tetraether index of lipids with 86 carbon atoms (TEX 86 ), was applied to the suspended particulate organic matter (POM) and sediment core tops from eight sites in the southern North Sea in different seasons. The TEX 86 -derived temperatures in many samples did not correlate with mean annual sea surface temperature (SST), but were shifted toward winter SST, apparently because Crenarchaeota are more abundant and metabolically active during periods of low primary production. This indicates that TEX 86 -derived SST estimates do not necessarily reflect annual mean SST and may provide essential information about seasonal SST palaeoreconstruction. High TEX 86 -derived SSTs were measured in the water of the river Rhine and in the sediment core tops and seawater from several stations in the southern North Sea. These sites were all characterised by important input of organic matter from soil and peat, as revealed by the relatively high values obtained with the new terrestrial proxy, the branched and isoprenoid tetraether (BIT) index. These data demonstrate that to reconstruct palaeotemperatures it is essential to estimate both TEX 86 and BIT indices to check that TEX 86 temperatures are not biased as a result of large terrestrial input. Important seasonal variations in TEX 86 -derived SST were also evident for the surface sediments of several stations characterised by extremely low sedimentation rates, indicating temporary settlement of laterally transported organic matter with a warmer temperature signal. This implies that sediment core top correlations between TEX 86 and mean annual SST should not be carried out in areas characterised by transient sediment deposition.

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“…The Rhine ROFI is, on average, concentrated within a 20-km-wide coastal strip, while it occasionally extends to a distance of almost 40 km offshore (de Kok 1996;de Ruijter et al 1997;van Alphen et al 1988). The tides in the southern bight of the North Sea are dominated by the lunar semi-diurnal tide (M2), with a significant solar semidiurnal (S2) component.…”

Section: Introductionmentioning

confidence: 99%

On the vertical structure of the Rhine region of freshwater influence

2006

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An idealised three-dimensional numerical model of the Rhine region of fresh water influence (ROFI) was set up to explore the effect of stratification on the vertical structure of the tidal currents. Prandle's dynamic Ekman layer model, in the case of zero-depth-averaged, crossshore velocities, was first used to validate the response of the numerical model in the case of barotropic tidal flow. Prandle's model predicted rectilinear tidal currents with an ellipse veering of up to 2%. The behaviour of the Rhine ROFI in response to both a neap and a spring tide was then investigated. For the given numerical specifications, the Rhine plume region was well mixed over the vertical on spring tide and stratified on neap tide. During spring conditions, rectilinear tidal surface currents were found along the Dutch coast. In contrast, during neap conditions, significant cross-shore currents and tidal straining were observed. Prandle's model predicted ellipse veering of 50%, and was found to be a good indicator of ellipticity magnitude as a function of bulk vertical eddy viscosity. The modelled tidal ellipses showed that surface currents rotated anti-cyclonically whereas bottom currents rotated cyclonically. This caused a semi-diurnal cross-shore velocity shearing which was 90°out of phase with the alongshore currents. This cross-shore shear subsequently acted on the horizontal density gradient in the plume, thereby causing a semi-diurnal stratification pattern, with maximum stratification around high water. The same behaviour was exhibited in simulations of a complete spring-neap tidal cycle. This showed a pattern of recurring stratification on neaps and de-stratification on springs, in accordance with observations collected from field campaigns in the 1990's. To understand the increase in ellipticities to 30% during neaps and the precise shape of the vertical ellipse structure, stratification has to be taken into account. Here, a full threedimensional numerical model was employed, and was found to represent the effect of de-coupling of the upper and lower layers due to a reduction of mixing at the pycnocline.

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A two-layer model of the Rhine plume

Cited by 23 publications

References 25 publications

Characterization of transport and deposition of terrestrial organic matter in the southern North Sea using the BIT index

Characterization of transport and deposition of terrestrial organic matter in the southern North Sea using the BIT index

Application of the TEX86 temperature proxy to the southern North Sea

On the vertical structure of the Rhine region of freshwater influence

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