Turbulent Convergent Tidal Fronts

Pingree, R. D.; Forster, G. R.; Morrison, Gerald L.

doi:10.1017/s0025315400058653

Cited by 101 publications

(47 citation statements)

References 8 publications

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“…Early studies by Reed (1971) and Chew and Berberian (1971) provided estimates of horizontal divergence based on the relative motion of drifters deployed in the Alaskan Stream and Gulf Stream, respectively. Other studies, such as Pingree et al (1974) and Matthews et al (1993), estimated dispersion with particular emphasis on episodic instances of convergence. In the latter study (using radar), convergence was noted in 4 out of 20 days of observations.…”

Section: Introductionmentioning

confidence: 99%

Estimates of dispersion from clustered-drifter deployments on the southern flank of Georges Bank

Manning

Churchill

2006

Deep Sea Research Part II: Topical Studies in Oceanography

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Data from 16 clustered-drifter deployments are used to examine horizontal dispersion on the southern flank of Georges Bank. The spreading rates of all clusters have an average of 1.6 km d -1 with a standard deviation of 1.8 km d -1 . Both "effective" and "apparent" diffusivities are calculated for each cluster. Their ranges (i.e., -54 to 757 m 2 s -1 for effective diffusivity) are related to differences in cluster size and proximity to the tidal mixing front. Cross-bank convergence is documented for nearly 40% of the clusters. This occurs especially for clusters with centroids within 10 km of the tidal mixing front location, as deduced from conductivity, temperature, and depth transects (CTD) conducted concurrently with the cluster deployments.Estimates of turbulent dispersion (distinct from shear effects) are derived by the method of

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Section: Introductionmentioning

confidence: 99%

Estimates of dispersion from clustered-drifter deployments on the southern flank of Georges Bank

Manning

Churchill

2006

Deep Sea Research Part II: Topical Studies in Oceanography

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“…The purpose of this paper is to address the dynamics of the aggregation of wintering divers in relation to meso-and coarse-scale features of the estuarine system by analysis of data collected over a series of cruises from 1986 to 1993, and composites of CZCS-Chl data collected over the German Bight from 1978 to 1986. Aggregations of sub-surface foraging piscivorous seabirds are commonly observed at fronts between mixed and stratified waters (Pingree et al 1974, Schneider 1982, Kinder et al 1983, Hémery et al 1986, Decker & Hunt 1996, Begg & Reid 1997. However, only 2 studies are available on the linkage between seabird aggregations and estuarine fronts: Uspenski (1956, Novaya Zemlya) and Briggs et al (1987, Gulf of the Farallones).…”

Section: Introductionmentioning

confidence: 99%

Impact of estuarine fronts on the dispersal of piscivorous birds in the German Bight

Skov¹,

Prins²

2001

Mar. Ecol. Prog. Ser.

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Survey data on seabird distribution at sea, hydrographic data and optical satellite data collected for the German Bight were used to analyse the variability of the distribution of wintering redthroated diver and black-throated diver Gavia stellata/arctica in relation to oscillations of the Jutland Coastal Current (JCC) and associated surface fronts. Data collected from hydrographic stations were summarised by means of principal component analysis; the first component, reflecting characteristics of the JCC, provided a satisfactory quantitative measurement of the average meso-scale habitat used by both species. The pelagic range of divers clearly followed the outer estuarine front between surface North Sea water and the JCC, which was located between the 20 and 30 m depth contours. Despite a highly transient trailing edge of the JCC, no divers were ever observed in North Sea water. Hydrographic as well as composited satellite CZCS (Coastal Zone Color Scanner) data indicated the presence of an inner front, spanning a stronger surface salinity gradient than the outer estuarine front. The inner estuarine front was located between mixed estuarine water, with salinities between 32 and 34 psu, and the core of the estuarine water mass from the river Elbe, with salinities below 32 psu. Seven-year composite images, produced from all available CZCS-Chl (chlorophyll) data taken over the German Bight during the Nimbus-7 mission, revealed the mean distribution of the inner estuarine front as a sharp gradient between the 15 and 20 m depth contours, extending less than 10 km in longitude. The variability of the inner estuarine front was measured over a series of cruises, and it indicated a quasi-stable structure; the prevailing position of the surface front was in a zone stretching from 07°30' E at Horns Reef (55°45' N) to 07°50' E south of Amrum Bank (54°30' N), except during easterly winds when the front was advected offshore as far as 6°50' E. The recorded patches of high densities of divers were almost confined to areas within 5 km distance from the mean frontal zone. The link between divers and the inner estuarine front seemed rather persistent, as peak densities coincided with the location of this front during all cruises, while lower densities were normally observed in the core Elbe water and in the mixed water outside the front. The authors suggest that the quasi-stability and strength of the inner estuarine front give rise to a predictable location of food resources (i.e. small fish) for divers in the German Bight. Our study highlights the potential for frontal structures of the JCC to influence the marine ecosystem of the southeastern North Sea.KEY WORDS: Estuarine fronts · German Bight · Seabird foraging · Red-throated/black-throated diver · Gavia stellata/arctica Resale or republication not permitted without written consent of the publisher

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“…In coastal systems, the format~on of zooplankton patches occurs at the scale of fronts, tidal processes and river plumes and is dominated by physical processes (Pingree et al 1974, Herman et al 1981, Gagnon & Lacroix 1982, Franks 1997. Tidal currents flowing through passes can upwell zooplankton (Thompson & Golding 1981, Thompson & Wolanski 1984 and can subsequently concentrate them in vortices and secondary circulation cells (Wolanski & Hamner 1988).…”

Section: Introductionmentioning

confidence: 99%

Comparative foraging ecology of planktivorous auklets in relation to ocean physics and prey availability

Hunt¹,

Russell²,

Coyle³

et al. 1998

Mar. Ecol. Prog. Ser.

141

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ABSTRACT. We tested the hypothesis that the spatial distributions of foraging least, crested and parakeet auklets (Aethia pusilla, A. cristatella and A. psittacula, respectively) in the shallow passes of the Aleutian Islands would be determined by physical mechanisms that control near-surface prey concentrations. We recorded currents using an Acoustic Doppler Current Profiler, volume scattering using 200 and 420 kHz scientific echosounders, and the numbers of foraging birds. Zooplankton were sampled using a multiple opening/closing net and environmental sampling system (MOCNESS). Prey choice of birds was ascertained by collecting foraging birds and examining their stomach contents. Most sampling occurred between 8 July and 6 August 1993, when we conducted 50 passages along a transect that crossed a sill between Unalga and Kavalga Islands, western Aleutian Islands, thereby samplinq the loraglng activity ot auklets at a variety of times of day and tidal phases. We found that the abundance of foraging individuals of each of the 3 auklet species was a function of tidal speed. Auklet species were selective about the species of prey taken. Regardless of tidal direct~on, crested auklets foraged on euphausiids upwclled on the upstream side of the pass, whereas least auklets consumed copepods concentrated in near-surface convergences on the downstream side. Parakeet auklets foraged over the top of the pass and took fish and invertebrates. Tidal speed and direction influenced the distance between the peak numbers of some, but not all, species of auklets. Auklet prey preferences dictated where they foraged in the pass and the physical mechanisms exploited for successful foraging. Thus, in this instance, resource partitioning by these closely related planktivores was enhanced by a spatial segregation forced by the physical processes that enhanced the availability of prey. Our findings emphasize the important role of physical processes in the structuring of marine communities.

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Turbulent Convergent Tidal Fronts

Cited by 101 publications

References 8 publications

Estimates of dispersion from clustered-drifter deployments on the southern flank of Georges Bank

Estimates of dispersion from clustered-drifter deployments on the southern flank of Georges Bank

Impact of estuarine fronts on the dispersal of piscivorous birds in the German Bight

Comparative foraging ecology of planktivorous auklets in relation to ocean physics and prey availability

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