Structure, strength and seasonality of the slope currents in the Bay of Biscay region

Pingree, R. D.; Cann, Bernard Le

doi:10.1017/s0025315400059117

Cited by 275 publications

(204 citation statements)

References 22 publications

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“…Near the shelf breaks, there are larger gradients often associated with slope currents and shelf breaks (Pingree and Le Cann 1990;Serpette et al 2006). There was little rainfall in 2005 and anomalously low river outflow, and this is not a region with large evaporation under low-wind conditions, so that we expect no large near-surface haline stratification most of the time.…”

Section: Introductionmentioning

confidence: 88%

Surface Salinity Measurements—COSMOS 2005 Experiment in the Bay of Biscay

Reverdin

Blouch

Boutin

et al. 2007

Journal of Atmospheric and Oceanic Technology

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Sea surface salinity (SSS) data were collected in the Bay of Biscay between April and November 2005. The major source of data is 15 surface drifters deployed during the COSMOS experiment in early April and early May 2005 [12 from the Scripps Instution of Oceanography (SIO) and 3 from METOCEAN]. This is complemented by thermosalinograph (TSG) data from four French research vessels and four merchant vessels, from salinity profiles collected by Argo profiling floats and CTD casts, and from surface samples during two cruises. Time during the two cruises was dedicated to direct inspection of the drifters, recovering some, and providing validation data. This dataset provides a unique opportunity to estimate the accuracy of the SSS data and to evaluate the long-term performance of the drifter salinities. Some of the TSG SSS data were noisy, presumably from bubbles. The TSG data from the research vessels needed to be corrected from biases, which are very commonly larger than 0.1 pss-78 (practical salinity scale), and which in some instances evolved quickly from day to day. These corrections are only available when samples were collected or ancillary data are available (e.g., from CTD profiles). The resulting accuracy of the corrected TSG dataset, which varies strongly in time, is discussed. The surface drifter SSS data presented anomalous daytime values during days with strong surface warming. These data had to be excluded from the dataset. The drifter SSS presented initial biases in the range 0.009 to Ϫ0.026 pss-78. The (usually) negative bias increased by an average of Ϫ0.007 pss-78 during the average 65-day period before the COSMOS-2 cruise on 22-27 June. High chlorophyll derived from satellite ocean color, and therefore high density of phytoplanktonic cells, is observed in Medium Resolution Imaging Spectrometer (MERIS)/Moderate Resolution Imaging Spectroradiometer (MODIS) composites during part of the period, in particular in late April or early May. No correlation was found between the change in bias and the estimated surface chlorophyll. Evolution during the following summer months is harder to ascertain. For three buoys, there is little change in bias, but for two others, there could have been an increase in bias by up to 0.03 or 0.04 pss-78 during July-August. Seven drifters were recovered in the autumn, which provide recovery or postrecovery estimates of the biases, suggesting in three cases (out of seven) a large (0.02-0.03 pss-78) increase in bias during the autumn months, but no significant increase for the other four drifters.

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Section: Introductionmentioning

confidence: 88%

Surface Salinity Measurements—COSMOS 2005 Experiment in the Bay of Biscay

Reverdin

Blouch

Boutin

et al. 2007

Journal of Atmospheric and Oceanic Technology

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“…where 10 3 g d 0X63 0X066j j, and q is the density of air (Saunders, 1977;Pingree and LeCann, 1990).…”

Section: Currentsmentioning

confidence: 99%

The shelf-edge current north-west of Ireland

White

Bowyer

1997

Ann. Geophys.

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Abstract. Measurements of the slope current at two locations north-west of Ireland have been made between April and December 1994, 40 m above the seabed in a water depth of 660 m. A persistent poleward alongslope current was observed at both locations, with measured means of 10 and 21 cm s À1 respectively. A CTD transect across the slope near one mooring indicated the presence of a light, warm, saline core of water at the shelf edge. Peak currents were y50 cm s À1 , with strongest mean¯ow at the location with steeper slope. Variability at sub-tidal periods, principally 2±5 and 11±12 days, was apparent. The shorter-period variability was well correlated with coastal sea-level variations measured at a land point near to one of the moorings. The variability in the slope current at this period appeared to be a result of the warm current core movement up/down slope, probably as a result of interaction with higher-mode shelf waves. Some suggestion of a bottom-trapped diurnal wave was also found at one location.

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“…Applying such a forcing to the Bay of Biscay yielded values of current which are close to those observed, i.e., typically 6 cm/s around 500 m depth [Pingree and Le Cann, 1989]. This slope current also undergoes seasonal variations with a maximum at the end of the summer [Pingree and Le Cann, 1990]. This could explain part of the differences observed between the model and measurements.…”

Section: Spatial Evolution Of the Rectified Tidementioning

confidence: 55%

Effect of barotropic tidal rectification on low‐frequency circulation near the shelf break in the northern Bay of Biscay

Pérenne¹,

Pichon²

1999

J. Geophys. Res.

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Abstract. Current meter data collected in the Bay of Biscay are used with a barotropic model to study the effect of the tidal rectification on the low-frequency circulation near the shelf break. Data collected at two different locations are analyzed and show that the tidal forcing terms and the low-frequency circulation are completely different at the two locations. In order to obtain a quantitative interpretation of these differences, a tidal forcing with both M2 and S2 waves is introduced in a barotropic tidal rectification model. We focus on the rectification process due to the "stretching of the water columns" alone, in the realistic case of large-amplitude topography. A first theoretical result is that the bichromatic forcing generates a nonlinear variation of the residual current which depends on only one nondimensional parameter. This parameter is a function of the barotropic flow and of the wave frequencies. A second result is that the low-frequency circulation generated by such a rectification process (including the two waves) is twice as large in spring tide than in neap tide. Finally, the model applied to both moorings confirms that the tidal rectification is much weaker at one mooring, the northwest one, than at the other, where the tidal rectification can explain 50% of the observed low-frequency circulation.

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Structure, strength and seasonality of the slope currents in the Bay of Biscay region

Cited by 275 publications

References 22 publications

Surface Salinity Measurements—COSMOS 2005 Experiment in the Bay of Biscay

Surface Salinity Measurements—COSMOS 2005 Experiment in the Bay of Biscay

The shelf-edge current north-west of Ireland

Effect of barotropic tidal rectification on low‐frequency circulation near the shelf break in the northern Bay of Biscay

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