scholarly journals On the warming and salinification of the Mediterranean outflow waters in the North Atlantic

2004 ◽  
Vol 31 (1) ◽  
Author(s):  
Rachel A. Potter
2021 ◽  
Author(s):  
Paula Lorenzo Sánchez ◽  
Leonardo Aragão

<p>The North Atlantic Oscillation (NAO) has been widely recognized as one of the main patterns of atmospheric variability over the northern hemisphere, helping to understand variations on the North Atlantic Jet (NAJ) position and its influence on storm-tracks, atmospheric blocking and Rossby Wave breaking. Among several relevant teleconnection patterns identified through different timescales, the most prominent ones are found for northern Europe during winter months, when positive (negative) phases of NAO are related to wetter (drier) conditions. Although it is not well defined yet, an opposite connection is observed for the Mediterranean region, where negative NAO values are often associated with high precipitation. Therefore, the main goal of this study is to identify which regions and periods of the year are the most susceptible to abundant NAO-related precipitation throughout the Italian Peninsula. For doing so, the last 42 years period (1979-2020) was analysed using the Fifth Generation ECMWF Atmospheric ReAnalysis of the Global Climate (ERA5). The NAO index was calculated using the Mean Sea Level Pressure (MSLP) extracted from the nearest gridpoints to Reykjavik, Ponta Delgada, Lisbon and Gibraltar, with a time resolution of one hour and horizontal spatial resolution of 0.25ºx0.25º. Both NAO index and MSLP time series were validated for different timescales (hourly, daily, monthly and seasonal) using the Automated Surface Observing System data and the Climatic Research Unit (CRU) high-resolution dataset (based on measured data). High correlations, ranging from 0.92 to 0.98, were found for all stations, timescales and evaluated parameters. To quantify the influence of NAO over the Mediterranean region, the monthly averaged ERA5 ‘total precipitation’ data over the Italian Peninsula [35-48º N; 5-20º E] were used. As expected, the results concerning NAO x Precipitation presented the best correlations when analysed monthly, confirming some of the already known NAO signatures over the Italian Peninsula: higher correlations during winter and over the Tyrrhenian coast, and lower correlations during summer and over the Apennines, the Adriatic Sea and the Ionian Sea. On the other hand, the precipitation over the Alps and the Tunisian coast presented a remarkable signature of positive NAO values that, despite a lower statistical significance (85-90%), is in agreement with recent findings of observational studies. In addition, significant negative correlations were identified for the spring and autumn months over the Tyrrhenian area. Among those, the high correlations found during May are particularly interesting, as they follow the behaviour described in recent studies performed using the same high-resolution dataset (ERA5), which have identified an increased number of cyclones over the Mediterranean during this month. This connection suggests that NAO could also be used to explore the potential penetration of the North Atlantic depressions into the Mediterranean Basin. </p><p>Keywords: NAO; Teleconnections; ERA5; ReAnalysis; Mediterranean; Climatology.</p>


2010 ◽  
Vol 10 (7) ◽  
pp. 1379-1391 ◽  
Author(s):  
K. M. Nissen ◽  
G. C. Leckebusch ◽  
J. G. Pinto ◽  
D. Renggli ◽  
S. Ulbrich ◽  
...  

Abstract. A climatology of cyclones with a focus on their relation to wind storm tracks in the Mediterranean region (MR) is presented. Trends in the frequency of cyclones and wind storms, as well as variations associated with the North Atlantic Oscillation (NAO), the East Atlantic/West Russian (EAWR) and the Scandinavian variability pattern (SCAND) are discussed. The study is based on the ERA40 reanalysis dataset. Wind storm tracks are identified by tracking clusters of adjacent grid boxes characterised by extremely high local wind speeds. The wind track is assigned to a cyclone track independently identified with an objective scheme. Areas with high wind activity – quantified by extreme wind tracks – are typically located south of the Golf of Genoa, south of Cyprus, southeast of Sicily and west of the Iberian Peninsula. About 69% of the wind storms are caused by cyclones located in the Mediterranean region, while the remaining 31% can be attributed to North Atlantic or Northern European cyclones. The North Atlantic Oscillation, the East Atlantic/West Russian pattern and the Scandinavian pattern all influence the amount and spatial distribution of wind inducing cyclones and wind events in the MR. The strongest signals exist for the NAO and the EAWR pattern, which are both associated with an increase in the number of organised strong wind events in the eastern MR during their positive phase. On the other hand, the storm numbers decrease over the western MR for the positive phase of the NAO and over the central MR during the positive phase of the EAWR pattern. The positive phase of the Scandinavian pattern is associated with a decrease in the number of winter wind storms over most of the MR. A third of the trends in the number of wind storms and wind producing cyclones during the winter season of the ERA40 period may be attributed to the variability of the North Atlantic Oscillation.


Author(s):  
Noureddine Abid ◽  
Amin Laglaoui ◽  
Abdelhay Arakrak ◽  
Mohammed Bakkali

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.


2020 ◽  
Author(s):  
Simon Blockley ◽  
Dustin White ◽  
Rhys Timms ◽  
Paul Lincoln ◽  
Simon Armitage ◽  
...  

<p>The nature and expression of climate change in the Eastern Mediterranean, the Levant and further into Arabia is of considerable interest across a range of communities. This is in part due to the need to understand the potential for future climate forcing on environments given the complex range of climatic forcing factors that play out in the region. These include the role of prevailing winds across the Mediterranean, Northerly winds pushing down into the region during cold glacial conditions, and the influence of the Afro-Arabian Monsoon. The last glacial to interglacial period is a critical window to examine such processes, as a range of climatic signals are recorded, many of which have been proposed as correlatives of events seen in the North Atlantic. Dating issues are as ever an issue when trying to precisely compare different climate archives. To address such, the INTIMATE event stratigraphy has been developed for the North Atlantic region, with recent extensions into parts of the Mediterranean. This couples the stratigraphic framework of the Greenland Ice core records as a regional stratotype, with  a number of tephra horizons in the North Atlantic and Europe, aiding the process of correlation. The last INTIMATE event stratigraphy coupled the extended GICC05 timescale for Greenland back to 128 b2k (Blockley et al., 2014). This paper reports on attempts to test the potential for tephrochronology to be extended into the Levant and potentially Arabia, through the identification of tephra layers in sediment focussing archives, such as archaeological cave sequences. We have examined tephra presence in archaeological sites, principally in Israel, that record sediment deposition from ~30ka BP through to >100ka BP. Analyses of these records show that tephra is present in almost all of the studied sites (e.g., Kebara, Tabun, Amud, Shovakh). Moreover, tephra in these sequences can be chemically correlated to known volcanic systems, demonstrating the potential going forward to analyse long lake and marine records around the region for cryptotephra. At the same time clear challenges are emerging. Firstly, there is a range of chemistry in many of the layers and careful analyses is needed to pick apart the geochemical signal and to identify reworking, as opposed to chemically heterogeneous ash layers from a single volcano. This process is complicated by the relatively limited range of published geochemical data from some volcanic centres. This presentation will outline the current state of knowledge of key volcanic centres, particularly in the Aegean and Turkey, alongside the new Levantine data, to consider the steps needed to establish a secure extension of the INTIMATE approach into this region.</p><p>Blockley, S., et al., 2014. Quaternary Science Reviews. 106, 88-100. doi:10.1016/j.quascirev.2014.11.002.</p>


Oryx ◽  
1965 ◽  
Vol 8 (3) ◽  
pp. 185-193
Author(s):  
Arthur G. Bourne

For several hundred years the small whales of the North Atlantic and the Mediterranean and Black Seas have been hunted with varying degrees of intensity. All too often the story has been one of overhunting followed by rapid decline of stocks, but so little is known about these small whales that today it is impossible to assess their populations or the effects of present hunting on the stocks. The author recounts the history of eight species of small whale and urges the need for more research to ensure planned cropping of a valuable resource. A Canadian proposal for whale hunting as a sport is perhaps a sign of a new danger to come.


Author(s):  
A. Sabatés ◽  
M. Demestre ◽  
P. Sanchez

The study of the morphological and meristic characters of larval and adult sandeels (Gymnammodytes spp.) collected off the Catalan coast (NW Mediterranean) has revealed the co-occurrence of G. cicerelus and G. semisquamatus in the Mediterranean. The geo-graphical distribution of G. semisquamatus had hitherto been thought to be limited to the European Atlantic coasts. The comparative analysis of specimens of G. semisquamatus from the Mediterranean and from the North Atlantic has demonstrated a marked latitudinal cline in the meristic counts. An exhaustive overview is presented of the bibliography referring to the Ammodytidae family in the Mediterranean, and the validity of the numerous references is discussed. Finally, it has been shown that the accepted description of G. cicerelus included the two species: G. cicerelus and G. semisquamatus. In the present paper an up-to-date diagnosis of both species is presented.


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