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  • 1
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    The Mediterranean water tongue and its chlorofluoromethane signal in the Iberian Basin in early summer 1989 (1993)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 98 (C5). p. 8405.
    Details
    Publication Date: 2019-09-23
    Description: Hydrographic observations from the Iberian Basin demonstrate the variability of water masses in upper and intermediate layers. The surveyed area embraces the internal front between water masses from higher latitudes and the Mediterranean outflow, exhibits several isolated Mediterranean eddy (meddy) structures at middepth, and displays the virtual source region for the Mediterranean Water (MW) tongue off the Portuguese continental slope. The description is enhanced by additional chlorofluoromethane measurements, which show anomalously high concentrations at middepth, due to mixing of MW with the overlying Atlantic waters in the Gulf of Cadiz. The geostrophic stream function shows several meddylike features that not only are remarkably extended in the depth range of the MW, but are also correlated with surface height anomalies.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/93JC00040
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    A view of the Canary Basin thermocline circulation in winter (1992)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 97 (C8). pp. 12495-12510.
    Details
    Publication Date: 2019-04-04
    Description: During January and February 1989 the recirculation of the subtropical gyre in the eastern North Atlantic was surveyed with a three-ship experiment. The analysis of hydrographic measurements and velocity data from a shipboard acoustic Doppler current profiler reveals the synoptic-scale circulation patterns and water mass distributions in the Canary Basin. The geostrophic transport stream function estimated with a horizontally varying reference level of no motion highlights the major currents in three layers representing the vertical structure of the horizontal circulation. The classical circulation scheme is shown by the stream function in the upper 200 m: the Azores, Canary, and North Equatorial currents. Unlike the deep-penetrating Azores Current, the Canary Current and the North Equatorial Current are restricted to the upper 200 m. Both carry North Atlantic Central Water along the water mass boundary with South Atlantic Central Water. South Atlantic Central Water flows through the passage between the Cape Verde archipelago and Africa via narrow currents into the area north of 14.5°N. At the southern edge of the subtropical gyre we identify an eastward flow of Antarctic Intermediate Water between 700 and 1200 m.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/92JC01095
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    New observations of Meddy Movement south of the Tejo Plateau (1992)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 19 (24). pp. 2389-2392.
    Details
    Publication Date: 2016-05-12
    Description: Mediterranean salt lenses (meddies) are a dominant factor in the salt budget of the Atlantic at middepth. In spite of their important role, their juvenile migration has not yet been directly observed. For the first time, two RAFOS float trajectories show strong evidence of a meddy along the Iberian continental slope off Lisbon. Over six weeks we obtained drift observations from two levels (629, 847 dbar). Both instruments recorded a series of loops with an azimuthal speed O (30 cm s−1) at a radius of about 25 km. Relatively high propagation speeds of several centimeters per second indicate the meddy was probably carried along with the undercurrent of Mediterranean Water. The Tejo Plateau, a prominent feature of the continental slope and a natural obstacle for the spreading Mediterranean Water tongue, appears to act as a deflector for advected meddies possibly formed by interaction of the undercurrent with the canyon-rich topography farther south.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/92GL02139
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  • 4
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    Deep Lenses of Circumpolar Water in the Argentine Basin (2002)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 107 (C1). 10.1029-10.1040.
    Details
    Publication Date: 2018-04-18
    Description: Three deep anticyclonic eddies of a species only reported once before [ Gordon and Greengrove, 1986 ] were intersected by hydrographic lines of the World Ocean Circulation Experiment (WOCE) and South Atlantic Ventilation Experiment (SAVE) programs in the Argentine Basin. The vortices are centered near 3500 m depth at the interface between North Atlantic Deep Water and Bottom Water. They have ∼1500-m-thick cores containing Lower Circumpolar Deep Water and a dynamic influence that may span up to two thirds of the water column. As one eddy was observed just downstream of the western termination of the Falkland Escarpment, a destabilization of the deep boundary current by the sudden slope relaxation is suggested as a potential cause of eddy formation. Besides isopycnal interleaving at the eddy perimeters, strongly eroded core properties in the upper parts of the lenses, associated with low density ratios, hint at double diffusion at the top of the structures as another major decay mechanism. The presence of an eddy in the northern Argentine Basin shows the possibility for a northward drift of the vortices, in this basin at least. Deep events in recent current measurements from the Vema Channel are presented that raise the question of further equatorward motion to the Brazil Basin.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2001JC000963
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  • 5
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    The complex spreading pattern of Mediterranean Water off the Portuguese continental slope (1990)
    Pergamon Press
    In:  Deep Sea Research Part A: Oceanographic Research Papers, 37 (12). pp. 1805-1823.
    Details
    Publication Date: 2020-08-04
    Description: Two stacked outflow cores of the Mediterranean Water undercurrent pass through a broad “gateway” between Cape St. Vincent and Gettysburg Bank entering the Iberian Basin. The upper core (depth ∼750 m, σ1=31.85) shows a strong tendency to follow the contours of the Portuguese continental rise. Yet, the lower core (depth ∼1250 m, σ1=32.25) primarily meanders west and northwestward forming large blobs of Mediterranean Water. The predominance of isolated Meddy structures embedded in a background field is reflected in a long-term current meter record from the deep Iberian Basin.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0198-0149(90)90079-B
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Seven-year current meter record in the eastern North Atlantic (1988)
    Pergamon Press
    In:  Deep Sea Research Part A: Oceanographic Research Papers, 35 (8). pp. 1259-1268.
    Details
    Publication Date: 2020-08-04
    Description: Continuous current measurements at the 1000 m level were obtained in the central Canary Basin of the northeast Atlantic near 33°N, 22°W for 2398 days. Even with this very long time series no statistically significant mean current could be estimated at that level, because the energetic fluctuations are large compared to the weak mean. In the eddy scale range, i.e. at current fluctuations are scales between 47 and 455 days, a pronounced anisotropy between zonal and meridional components is apparent. For the first time in the subtropical North Atlantic gyre our data allow confirmation of the expected spectral decrease beyond the eddy scale peak in an eastern basin. With respect to future global experiments we wonder if our results from an eastern basin location are representative for the general circulation at mid-ocean sites?
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0198-0149(88)90082-9
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  • 7
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    Westward bottom currents along the margin of the South Shetland Island Arc (1988)
    Pergamon Press
    In:  Deep Sea Research Part A: Oceanographic Research Papers, 35 (2). pp. 269-301.
    Details
    Publication Date: 2020-08-04
    Description: Existing information is synthesized and new data presented to describe the flow of near-bottom water from the Weddell Sea into the Scotia Sea and westward through Drake Passage along the continental slope. The water characteristics and currents along the northern margins of the South Sandwich Island Arc are examined. Long-term current measurements in the bottom waters at locations over the outer shelf and slope and along the continental rise show persistent flow from Atlantic to Pacific along isobaths at speeds of 10–20 cm s−1. Three sources for the waters in these currents are identified and discussed. At the deepest levels, Weddell Sea Deep Water enters the Scotia Sea near 40°W through a depression in the South Scotia Arc and then flows westward, constrained by the bottom topography. This cold, fresh, oxygenated bottom water then flows west to enter Drake Passage via a gap in the Shackleton Fracture Zone at the base of the continental slope northwest of Elephant Island. Mid-depth water may flow from the Weddell Sea to the Scotia Sea through the Powell Basin (sill depth approximately 2000 m) located west of South Orkney Island near 48°W. The westward flowing waters along the shelf and upper continental slope, which are denser than those immediately offshore, may be a continuation of the Polar Slope Current from the Weddell Sea or may be derived principally by convection from the shelves of the South Sandwich Island Arc. A vertical section north of Elephant Island shows downslope convection off the shelf, analogous to the observed at many locations around Antartica.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0198-0149(88)90040-4
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  • 8
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    Cape Verde Frontal Zone (1991)
    Pergamon Press
    In:  Deep Sea Research Part A: Oceanographic Research Papers, 38 (S1). S505-S530.
    Details
    Publication Date: 2020-08-05
    Description: The term Cape Verde Frontal Zone is introduced to characterize the southeastern corner of the subtropical gyre circulation in the North Atlantic Ocean far west of the upwelling area off the Mauretanean shelf. Two water mass fronts, one overlying the other, are identified with a quasi-synoptic set of CTD-OZ and nutrient data from November 1986. In the warm water sphere we encounter North and South Atlantic Central Water (NACWISACW) superimposed on extensions of Mediterranean outflow and Antarctic Intermediate Water. The Central Water Boundary, as the separator of NACW from SACW, represents the southeastern side of the Canary/North Equatorial Current system. It acts as a barrier between the well-ventilated, nutrient-poor inner part of the basin-wide circulation of the North Atlantic and the shadow zone with its lowly oxygenated and nutrified cross-equatorial influx. Year-long current meter records, having fluctuations over typical time scales of 5(1`90 days, attest to the highly variable nature of the Cape Verde Frontal Zone. Incidentally, we observe in the data an intrathermocline eddy, called Meddy BIRGIT, which has a double maximum in the vertical salinity structure. Simultaneous Lagrangian observations by RiCHAttDSON et al. (1989, Journal of Physical Oceanography, 19, 371-383) confirm the expected anticyclonic motion of this salt lens, which must have travelled without significant mixing for at least 2500 km from its likely generation region in the Gulf of Cadiz.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0198-0149(12)80022-7
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  • 9
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    Wind measurements from an array of oceanographic moorings and from F/SMeteor during JASIN 1978 (2012)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 88 (C14). pp. 9689-9705.
    Details
    Publication Date: 2019-04-04
    Description: During the Joint Air-Sea Interaction (JASIN) experiment conducted in the northern Rockall Trough in the summer of 1978, oceanographic moorings with surface buoys carrying wind recorders were deployed in an array designed to investigate the variability of the near-surface wind field at scales of from 2 to 200 km. The wind records together with observations taken on board the research vessels participating in JASIN have provided ground truth measurements for the sea surface wind velocity sensors on the Seasat satellite. During most of the experiment the wind field was characterized by spatial scales large in comparison with the separations between the buoys. On several occasions, spatial differences associated with cold fronts were identified, and it was possible to track the passage of the front through the array. However, quantitative analysis of the variability of the wind field was complicated both by a lack of data due to mechanical failures of some instruments and by significant differences in the performance of the diverse types of wind recorders. Reevaluation of the instruments used in JASIN and recent comparison of some of these instruments with more conventional sets of wind sensors confirm the possibility that there is significant error in the JASIN wind measurements made from the buoys. In particular, the vector-averaging wind recorder on W2, which was one of the few instruments to recover a full length record and which was chosen during a Seasat-JASIN workshop as the JASIN standard, had performance characteristics that were among the most difficult to explain.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/JC088iC14p09689
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  • 10
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    On the stationarity of temperature spectra at high horizontal wave numbers (2012)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 80 (27). pp. 3885-3891.
    Details
    Publication Date: 2019-04-04
    Description: Two examples of high wave number (one cycle per 5 m to one cycle per kilometer) temperature spectra from constant depth tow segments are presented. The first is from observations in the center of the main thermocline of the northwest Atlantic at a depth of about 700 m. Four independent estimates of the spectrum are statistically similar to one another. The result is continuous with previous results at lower wave numbers and compares favorably with the 1975 Garrett and Munk internal wave model prediction. The second example is from a tow through a surface mixed layer, at a depth of 26 m, in a nearby area. In contrast to the above, it describes the lack of stationarity of the near-surface spectrum; a result reminiscent of the frequency spectra observed by Sabinin.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/JC080i027p03885
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