Residual Drift near the Sea Bed in Liverpool Bay: an Observational Study

Halliwell, A. Roy

doi:10.1111/j.1365-246x.1973.tb05843.x

Cited by 20 publications

(13 citation statements)

References 11 publications

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“…The current's vertical structure is discussed in Polton et al (2013) as a result of a depth varying competition between horizontal density and sea surface slope induced pressure gradients. More generally, however, both bottom drifter (Halliwell, 1973) and ADCP measurements (Polton et al, 2011) show that the near bed mean currents are consistently shoreward, near surface current measurements are presented below.…”

Section: Introductionmentioning

confidence: 83%

“…This circulation has also been well studied - Bowden & Sharaf El Din (1966b), Ramster & Hill (1969), Halliwell (1973), Heaps & Jones (1977, Howarth (1984), Czistrom (1986. In particular Heaps & Jones (1977) postulate that wind effects on top of the density driven circulation introduce an additional mode -a clockwise density driven depth-averaged coastal circulation occurring when winds are less than 5 -10 m s -1 and an anti-clockwise coastal circulation occurring when winds are stronger.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of coastal density gradients near a macro-tidal estuary: Application to the Mersey and Liverpool Bay

Howarth¹,

Balfour²,

Player³

et al. 2014

Continental Shelf Research

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Density gradients in coastal regions with significant freshwater input are large and variable and are a major control of nearshore circulation. However their measurement is difficult, especially where the gradients are largest, close to the coast, with significant uncertainties because of a variety of factors -time and spatial (horizontal and vertical) scales are small, tidal currents are strong and water depths shallow. Whilst temperature measurements are relatively straightforward, measurement of salinity (the dominant control of spatial variability for density) can be less reliable in turbid coastal waters. 2The nearshore density gradients in Liverpool Bay are investigated using an integrated multiyear data set from an in situ buoy, instrumented ferry and HF radar. The ferry is particularly useful for estimating coastal density gradients since measurements are made right from the mouth of Mersey, where gradients are on average 3x10 -4 kg m -4 . Using measurements at the single in situ site by the Mersey Bar, 17 km from land, density gradients can be estimated from the tidal excursion or by using ferry data; both giving average values of 5x10 -5 kg m -4 .Nine years of surface salinity measurements there show no evidence of predominant periodicities, although there is a weak annual cycle, and no consistent relation with storms or floods, leading to the conclusion that the majority of the Mersey plume, for most of the time, lies closer to the English shore than the Mersey Bar. Liverpool Bay's circulation is the dominant factor, with wind forcing tending to reinforce it for wind speeds greater than 5 -10 m s -1 . Near bed currents are consistently shoreward and near surface currents northward.

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Section: Introductionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Assessment of coastal density gradients near a macro-tidal estuary: Application to the Mersey and Liverpool Bay

Howarth¹,

Balfour²,

Player³

et al. 2014

Continental Shelf Research

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“…5 and 6). This infilling was further assisted by dredge spoil drifting into the channels from dump sites on Taylor's Bank and Great Burbo Bank (Halliwell, 1973). Reduced ebb flow also gave the strengthened flood tide a longer time period to move sediment inshore, causing an eastward migration of Taylor's Bank and Great Burbo Bank.…”

Section: Channel Training and Dredgingmentioning

confidence: 98%

Long-term morphological change and its causes in the Mersey Estuary, NW England

Blott¹,

Pye²,

Wal

et al. 2006

Geomorphology

139

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“…The results of the above work were able to explain the main features of the residual currents in Liverpool Bay deduced on the one hand from a long-term current meter station (Ramster 1972) and on the other hand from an extensive programme of bottom drifter experiments (Halliwell 1973). Broadly, these observations indicated the presence of a bottom drift to the south or southeast going towards the shores of the Bay and a surface drift to the north directed out of the region.…”

Section: Introductionmentioning

confidence: 65%

Density currents in the Irish Sea

Heaps

Jones

1977

Geophysical Journal International

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Summary. Density currents in the Irish Sea are evaluated using a three‐dimensional numerical model. Regimes of current are derived from two horizontal σt distributions representative of 1972 September 17—October 6 and 1971 September 6–20, respectively. Most consideration is given to the circulation of the eastern Irish Sea — defined as that sea area lying to the east of a line joining Anglesey to the Isle of Man, including Liverpool Bay. Here, it is found that water enters near the sea bottom moving generally eastwards towards the coast of Northwest England and, after upwelling, leaves near the sea surface moving in directions between west and north. The vertically integrated flow then constitutes a clockwise gyre, giving support, for the first time from hydrodynamics, to a residual circulation earlier inferred from biological observations. As part of this gyre, there is a south‐going stream along the English coast. Comparing the density currents with wind‐induced currents (also derived from the numerical model) it is demonstrated that the latter predominate for wind speeds above 5–10 m/s. Results obtained indicate that a common sequence of winds, changing in direction from southeast round to west, induces an anticlockwise circulation in the eastern Irish Sea in agreement with a residual circulation pattern earlier deduced from current measurements and drifter experiments. The density currents form a north‐going flow of water through the Irish Sea which bifurcates around the Isle of Man, most of it passing to the west of the Isle. Southerly‐type winds also maintain a northwards flow through the Sea, most of this passing to the east of the Isle. It is shown that the magnitude of the computed north‐going density flow is significantly dependent on the nature of the numerical model's open boundary conditions — these being applied across the North Channel (in the north) and across St George's Channel (in the south). The pattern of density current in the eastern Irish Sea, and particularly in Liverpool Bay, appears to be relatively insensitive to alterations in these conditions.

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Residual Drift near the Sea Bed in Liverpool Bay: an Observational Study

Cited by 20 publications

References 11 publications

Assessment of coastal density gradients near a macro-tidal estuary: Application to the Mersey and Liverpool Bay

Assessment of coastal density gradients near a macro-tidal estuary: Application to the Mersey and Liverpool Bay

Long-term morphological change and its causes in the Mersey Estuary, NW England

Density currents in the Irish Sea

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