On the Source of Mediterranean Overflow Water Property Changes

2009 ◽  
Vol 39 (8) ◽  
pp. 1800-1817 ◽  
Author(s):  
M. Susan Lozier ◽  
Laurie Sindlinger
Keyword(s):  
North Atlantic ◽  
Strait Of Gibraltar ◽  
Minimal Impact ◽  
Marginal Seas ◽  
The North ◽  
Freshwater Fluxes ◽  
The Mediterranean ◽  
Eastern North Atlantic ◽  
Property Changes ◽  
Source Waters

Abstract A recent study of the eastern North Atlantic detailed significant increases in the temperature and salinity of the Mediterranean Overflow Water (MOW) from 1950 to 2000. To examine the degree to which the source waters, which spill over the sill at the Strait of Gibraltar, could be responsible for these observations in the open Atlantic, a box model of water mass transformation by marginal seas was employed. Time series for the salinity of the inflowing North Atlantic surface waters, freshwater fluxes in the Mediterranean (evaporation and precipitation and river runoff), and the volumetric flow rates for the inflow and outflow across the Strait of Gibraltar were used to predict the salinity of the source waters to the North Atlantic from 1950 to 2000. Results from this calculation reveal that source water changes have minimal impact on MOW property changes on interannual and decadal time scales. It is suggested instead that circulation changes within the open Atlantic alter the advective–diffusive pathways of MOW such that property changes within the MOW reservoir are created.

The reproductive biology of swordfish (Xiphias gladius) in the Strait of Gibraltar

2018 ◽  
Vol 99 (3) ◽  
pp. 649-659 ◽  
Author(s):  
Noureddine Abid ◽  
Amin Laglaoui ◽  
Abdelhay Arakrak ◽  
Mohammed Bakkali
Keyword(s):  
Mediterranean Sea ◽  
North Atlantic ◽  
Fork Length ◽  
Strait Of Gibraltar ◽  
Mixing Rate ◽  
The North ◽  
Lower Jaw ◽  
The North Atlantic ◽  
The Mediterranean ◽  
First Maturity

During the period from April to September for the years 2014–2016, 998 swordfishes caught by the Moroccan artisanal longline fishery in the Strait of Gibraltar were sampled to study the reproduction of this species in this mixing area between the Mediterranean Sea and the North Atlantic. The results showed that the sex ratio is slightly in favour of males for sizes smaller than 130 cm LJFL (Lower jaw-fork length), whereas females are more numerous in sizes larger than 140 cm LJFL. Fifty per cent of females were estimated to be mature at 170 cm LJFL, while for males, the size at first maturity was estimated to be 95 cm LJFL. The swordfish spawn from June to September, probably in the Mediterranean Sea. The findings of this study suggest that the reproductive characteristics of swordfish caught in the Strait of Gibraltar are similar to those of the Mediterranean swordfish, and a high mixing rate between the Mediterranean and the North Atlantic stocks occurs in the study area.

scholarly journals A Model Analysis of the Behavior of the Mediterranean Water in the North Atlantic

2007 ◽  
Vol 37 (3) ◽  
pp. 764-786 ◽  
Author(s):  
Yanli Jia ◽  
Andrew C. Coward ◽  
Beverly A. de Cuevas ◽  
David J. Webb ◽  
Sybren S. Drijfhout
Keyword(s):  
North Atlantic ◽  
Current System ◽  
Global Ocean ◽  
Western Boundary ◽  
Depth Range ◽  
Strait Of Gibraltar ◽  
The North ◽  
The North Atlantic ◽  
The Mediterranean ◽  
Mediterranean Water

Abstract The behavior of the Mediterranean Water in the North Atlantic Ocean sector of a global ocean general circulation model is explored, starting from its entry point at the Strait of Gibraltar. The analysis focuses primarily on one experiment in which explicit watermass exchange between the Mediterranean Sea and the Atlantic at the Strait of Gibraltar is permitted. The model produces an exchange rate of approximately 1 Sv (Sv ≡ 106 m3 s−1). This is comparable to estimates derived from field measurements. The density of the Mediterranean outflow, however, is lower than observed, mainly because of its high temperature (more than 2°C higher than in reality). The lower density of the outflow and the model’s inadequate representation of the entrainment mixing in the outflow region cause the Mediterranean Water to settle in a depth range ∼800–1000 m in the North Atlantic, about 200 m shallower than observed. Here an interesting current system forms in response to the intrusion of the Mediterranean Water, involving three main pathways. In the first, the Mediterranean Water heads roughly westward across the basin and joins the deep western boundary current. In the second, the water travels northward along the eastern boundary reaching as far as Iceland, where it turns westward to participate in the deep circulation of the subpolar gyre. In the third, the water initially moves westward to the central Atlantic just north of 30°N before turning northwestward to reach an upwelling region at the Grand Banks off Newfoundland. At this location, the saline Mediterranean Water is drawn upward to the ocean upper layer and entrained into the North Atlantic Current system flowing to the northeastern basin; part of the current system enters the Nordic seas.

scholarly journals Teleconnection between the Atlantic Meridional Overturning Circulation and Sea Level in the Mediterranean Sea

2019 ◽  
Vol 32 (3) ◽  
pp. 935-955 ◽  
Author(s):  
Denis L. Volkov ◽  
Molly Baringer ◽  
David Smeed ◽  
William Johns ◽  
Felix W. Landerer
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
North Atlantic ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Strait Of Gibraltar ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic ◽  
The Mediterranean

The Mediterranean Sea can be viewed as a “barometer” of the North Atlantic Ocean, because its sea level responds to oceanic-gyre-scale changes in atmospheric pressure and wind forcing, related to the North Atlantic Oscillation (NAO). The climate of the North Atlantic is influenced by the Atlantic meridional overturning circulation (AMOC) as it transports heat from the South Atlantic toward the subpolar North Atlantic. This study reports on a teleconnection between the AMOC transport measured at 26.5°N and the Mediterranean Sea level during 2004–17: a reduced/increased AMOC transport is associated with a higher/lower sea level in the Mediterranean. Processes responsible for this teleconnection are analyzed in detail using available satellite and in situ observations and an atmospheric reanalysis. First, it is shown that on monthly to interannual time scales the AMOC and sea level are both driven by similar NAO-like atmospheric circulation patterns. During a positive/negative NAO state, stronger/weaker trade winds (i) drive northward/southward anomalies of Ekman transport across 26.5°N that directly affect the AMOC and (ii) are associated with westward/eastward winds over the Strait of Gibraltar that force water to flow out of/into the Mediterranean Sea and thus change its average sea level. Second, it is demonstrated that interannual changes in the AMOC transport can lead to thermosteric sea level anomalies near the North Atlantic eastern boundary. These anomalies can (i) reach the Strait of Gibraltar and cause sea level changes in the Mediterranean Sea and (ii) represent a mechanism for negative feedback on the AMOC.

Morphological and genetic variation in the North Atlantic copepod, Centropages typicus

2011 ◽  
Vol 92 (1) ◽  
pp. 99-106 ◽  
Author(s):  
Claudia Castellani ◽  
Alistair J. Lindley ◽  
Marianne Wootton ◽  
Christopher M. Lee ◽  
Richard R. Kirby
Keyword(s):  
Genetic Differentiation ◽  
North Atlantic ◽  
Haplotype Diversity ◽  
Mitochondrial Haplotype ◽  
Morphological Variations ◽  
Population Genetic Differentiation ◽  
The North ◽  
The Mediterranean ◽  
Eastern North Atlantic ◽  
Centropages Typicus

This study describes phenotypic and genotypic variations in the planktonic copepod, Centropages typicus (Copepoda: Calanoida) that indicate differentiation between geographical samples. We found consistent differences in the morphology of the chela of the sexually modified fifth pereiopod (P5) of male C. typicus between samples from the Mediterranean, western North Atlantic and eastern North Atlantic. A 560 base pairs (bp) region of the C. typicus mitochondrial cytochrome c oxidase subunit I (COI) and a 462 bp fragment of the nuclear rDNA internal transcribed spacer (ITS) tandem array were analysed to determine whether these morphological variations reflect population genetic differentiation. Mitochondrial haplotype diversity was found to be high with 100 unique COI haplotypes among 116 individuals. Analysis of mtCOI variation suggested differentiation between the Mediterranean and Atlantic populations but no separation was detected within the Atlantic. Intragenomic variation in the ITS array suggested genetic differentiation between samples from the western North Atlantic and those from the eastern North Atlantic and Mediterranean. Breeding experiments would be required to elucidate the extent of genetic isolation between C. typicus from the different population centres.

scholarly journals About the seasonal and fortnightly variabilities of the Mediterranean outflow

Ocean Science ◽  
2011 ◽  
Vol 7 (3) ◽  
pp. 421-428 ◽  
Author(s):  
C. Millot ◽  
J. Garcia-Lafuente
Keyword(s):  
Time Series ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Internal Tide ◽  
Atlantic Water ◽  
Strait Of Gibraltar ◽  
The North ◽  
Mediterranean Outflow ◽  
The Mediterranean

Abstract. CTD time series from the HYDRO-CHANGES programme and INGRES projects have been collected simultaneously (2004–2008) on the shelf of Morocco and at the sills of Camarinal and Espartel in the strait of Gibraltar. They provide information that supports results recently obtained from the analysis of the two former time series, as well as from a reanalysis of GIBEX CTD profiles (1985–1986). The outflow of Mediterranean Waters, which does not show a clear seasonal variability before entering the strait, strongly mixes within the strait, due mainly to the internal tide, with the seasonally variable inflow of Atlantic Water. The outflow thus gets marked seasonal and fortnightly variabilities within the strait. Furthermore, since the outflowing waters entering the strait display marked spatial heterogeneity and long-term temporal variabilities, accurately predicting the characteristics of the Mediterranean outflow into the North Atlantic Ocean appears almost impossible.

scholarly journals <i>Syracosphaera noroiticus</i> sp. nov., and <i>S. marginaporata</i> sp. nov., (Syracosphaeraceae, Prymnesiophyta), new coccolithophorids from the Mediterranean Sea and North Atlantic Ocean

1993 ◽  
Vol 12 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Michael Knappertsbusch
Keyword(s):  
Atlantic Ocean ◽  
Mediterranean Sea ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Undescribed Species ◽  
The North ◽  
The North Atlantic ◽  
The Mediterranean ◽  
Eastern North Atlantic ◽  
Scanning Electron

Abstract. During scanning electron microscope investigations of living coccolithophorids from the Mediterranean Sea and the North Atlantic Ocean, two hitherto undescribed species of the genus Syracosphaera Lohmann, 1902 emend. Gaarder (in Gaarder and Heimdal, 1977) were found. The first species, Syracosphaera noroiticus sp. nov., was recorded in the Gulf of Lyons (Mediterranean Sea), and the second, S. marginaporata sp. nov., was found in the eastern North Atlantic.

First record of Norwegian killer whales attacking and feeding on a harbour porpoise

2015 ◽  
Vol 8 ◽  
Author(s):  
A. Mel Cosentino
Keyword(s):  
North Atlantic ◽  
Marine Mammals ◽  
First Record ◽  
Harbour Porpoise ◽  
Sperm Whales ◽  
Killer Whales ◽  
Strait Of Gibraltar ◽  
Cetacean Species ◽  
The North ◽  
Northern Bottlenose Whales

Orcinus orcais a cosmopolitan species and the most widely distributed marine mammal. Its diet includes over 140 species of fish, cephalopods, sea birds and marine mammals. However, many populations are specialised on certain specific prey items. Three genetically distinct populations have been described in the North Atlantic. Population A (that includes the Icelandic and Norwegian sub-populations) is believed to be piscivorous, as is population C, which includes fish-eating killer whales from the Strait of Gibraltar. In contrast, population B feeds on both fish and marine mammals. Norwegian killer whales follow the Norwegian spring spawning herring stock. The only description in the literature of Norwegian killer whales feeding on another cetacean species is a predation event on northern bottlenose whales in 1968. Daily land-based surveys targeting sperm whales were conducted from the Andenes lighthouse using BigEyes®binoculars (25×, 80 mm). The location of animals at sea was approximated through the use of an internal reticule system and a graduated wheel. On 24 June 2012 at 3:12 am, an opportunistic sighting of 11 killer whales was made off Andenes harbour. The whales hunted and fed on a harbour porpoise. Despite these species having overlapping distributions in Norwegian waters, this is the first predatory event reported in the literature.

Temperature, Salinity and Plankton in the Eastern North Atlantic and Coastal Waters of Britain, 1957.: I. The Characterisation and Distribution of Surface Waters

1963 ◽  
Vol 20 (3) ◽  
pp. 789-826 ◽  
Author(s):  
B. McK. Bary
Keyword(s):  
North Sea ◽  
North Atlantic ◽  
Coastal Waters ◽  
Water Bodies ◽  
English Channel ◽  
Oceanic Water ◽  
Climatic Fluctuations ◽  
The North ◽  
The North Sea ◽  
Eastern North Atlantic

Monthly temperature-salinity diagrams for 1957 have demonstrated that three surface oceanic "water bodies" were consistently present in the eastern North Atlantic; two are regarded as modified North Atlantic Central water which give rise to the third by mixing. As well in the oceanic areas, large and small, high or low salinity patches of water were common. Effects of seasonal climatic fluctuations differed in the several oceanic water bodies. In coastal waters, differences in properties and in seasonal and annual cycles of the properties distinguish the waters from the North Sea, English Channel and the western entrance to the Channel.The geographic distributions of the oceanic waters are consistent with "northern" and "southern" water bodies mixing to form a "transitional" water. Within this distribution there are short-term changes in boundaries and long-term (seasonal) changes in size of the water bodies.Water in the western approaches to the English Channel appeared to be influenced chiefly by the mixed, oceanic transitional water; oceanic influences in the North Sea appear to have been from northern and transitional waters.

A longitudinal study of humpback whales in Irish waters

2015 ◽  
Vol 96 (4) ◽  
pp. 877-883 ◽  
Author(s):  
Conor Ryan ◽  
Pádraig Whooley ◽  
Simon D. Berrow ◽  
Colin Barnes ◽  
Nick Massett ◽  
...  
Keyword(s):  
Longitudinal Study ◽  
North Atlantic ◽  
Spatial Scales ◽  
Humpback Whales ◽  
Migratory Species ◽  
The Public ◽  
Photo Identification ◽  
The North ◽  
Breeding Grounds ◽  
Eastern North Atlantic

Knowledge on the ecology of humpback whales in the eastern North Atlantic is lacking by comparison with most other ocean basins. Humpback whales were historically over-exploited in the region and are still found in low relative abundances. This, coupled with their large range makes them difficult to study. With the aim of informing more effective conservation measures in Ireland, the Irish Whale and Dolphin Group began recording sightings and images suitable for photo-identification of humpback whales from Irish waters in 1999. Validated records submitted by members of the public and data from dedicated surveys were analysed to form a longitudinal study of individually recognizable humpback whales. The distribution, relative abundance and seasonality of humpback whale sighting records are presented, revealing discrete important areas for humpback whales in Irish coastal waters. An annual easterly movement of humpback whales along the southern coast of Ireland is documented, mirroring that of their preferred prey: herring and sprat. Photo-identification images were compared with others collected throughout the North Atlantic (N = 8016), resulting in matches of two individuals between Ireland and Iceland, Norway and the Netherlands but no matches to known breeding grounds (Cape Verde and West Indies). This study demonstrates that combining public records with dedicated survey data is an effective approach to studying low-density, threatened migratory species over temporal and spatial scales that are relevant to conservation and management.

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