scholarly journals Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

Ocean Science ◽  
2014 ◽  
Vol 10 (3) ◽  
pp. 439-457 ◽  
Author(s):  
T. Stöven ◽  
T. Tanhua
Keyword(s):  
Deep Water ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Inverse Gaussian ◽  
Ionian Sea ◽  
One Dimensional ◽  
Levantine Basin ◽  
The Mean ◽  
The Mediterranean ◽  
Transient Tracer

Abstract. Ventilation is the primary pathway for atmosphere–ocean boundary perturbations, such as temperature anomalies, to be relayed to the ocean interior. It is also a conduit for gas exchange between the interface of atmosphere and ocean. Thus it is a mechanism whereby, for instance, the ocean interior is oxygenated and enriched in anthropogenic carbon. The ventilation of the Mediterranean Sea is fast in comparison to the world ocean and has large temporal variability. Here we present transient tracer data from a field campaign in April 2011 that sampled a unique suite of transient tracers (SF6, CFC-12, 3H and 3He) in all major basins of the Mediterranean. We apply the transit time distribution (TTD) model to the data in order to constrain the mean age, the ratio of the advective / diffusive transport and the number of water masses significant for ventilation. We found that the eastern part of the eastern Mediterranean can be reasonably described with a one-dimensional inverse Gaussian TTD (IG-TTD), and thus constrained with two independent tracers. The ventilation of the Ionian Sea and the western Mediterranean can only be constrained by a linear combination of IG-TTDs. We approximate the ventilation with a one-dimensional, two inverse Gaussian TTD (2IG-TTD) for these areas and demonstrate a possibility of constraining a 2IG-TTD from the available transient tracer data. The deep water in the Ionian Sea has a mean age between 120 and 160 years and is therefore substantially older than the mean age of the Levantine Basin deep water (60–80 years). These results are in contrast to those expected by the higher transient tracer concentrations in the Ionian Sea deep water. This is partly due to deep water of Adriatic origin having more diffusive properties in transport and formation (i.e., a high ratio of diffusion over advection), compared to the deep water of Aegean Sea origin that still dominates the deep Levantine Basin deep water after the Eastern Mediterranean Transient (EMT) in the early 1990s. The tracer minimum zone (TMZ) in the intermediate of the Levantine Basin is the oldest water mass with a mean age up to 290 years. We also show that the deep western Mediterranean has contributed approximately 40% of recently ventilated deep water from the Western Mediterranean Transition (WMT) event of the mid-2000s. The deep water has higher transient tracer concentrations than the mid-depth water, but the mean age is similar with values between 180 and 220 years.

scholarly journals Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

2013 ◽  
Vol 10 (5) ◽  
pp. 1647-1705 ◽  
Author(s):  
T. Stöven ◽  
T. Tanhua
Keyword(s):  
Mediterranean Sea ◽  
Deep Water ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Inverse Gaussian ◽  
Ionian Sea ◽  
Levantine Basin ◽  
The Mean ◽  
The Mediterranean ◽  
Transient Tracer

Abstract. Ventilation is the prime pathway for ocean surface perturbations, such as temperature anomalies, to be relayed to the ocean interior. It is also the conduit for gas exchange between atmosphere and ocean and thus the mechanism whereby, for instance, the interior ocean is oxygenated and enriched in anthropogenic carbon. The ventilation of the Mediterranean Sea is fast in comparison to the world ocean and has large temporal variability, so that quantification of Mediterranean Sea ventilation rates is challenging and very relevant for Mediterranean oceanography and biogeochemistry. Here we present transient tracer data from a field-campaign in April 2011 that sampled a unique suite of transient tracers (SF6, CFC-12, tritium and 3He) in all major basins of the Mediterranean. We apply the Transit Time Distribution (TTD) model to the data which then constrain the mean age, the ratio of the advective/diffusive transport mechanism, and the presence, or not, of more than one significant (for ventilation) water mass. We find that the eastern part of the Eastern Mediterranean can be reasonable described with a one dimensional Inverse Gaussian (1IG) TTD, and thus constrained with two independent tracers. The ventilation of the Ionian Sea and the Western Mediterranean can only be constrained by a multidimensional TTD. We approximate the ventilation with a two-dimensional Inverse Gaussian (2IG) TTD for these areas and demonstrate one way of constraining a 2IG-TTD from the available transient tracer data. The deep water in the Ionian Sea has higher mean ages than the deep water of the Levantine Basin despite higher transient tracer concentrations. This is partly due to the deep water of Adriatic origin having more diffusive properties in the transport and formation, i.e. a high ratio of diffusion over advection, compared to the deep water of Aegean Sea origin that still dominates the deep Levantine Basin deep water after the Eastern Mediterranean Transient (EMT) in the early 1990s. We also show that the deep Western Mediterranean has approximately 40% contribution of recently ventilated deep water from the Western Mediterranean Transition (WMT) event of the mid-2000s. The deep water has higher transient tracer concentrations than the mid-depth water, but the mean age is similar.

scholarly journals Changes in ventilation of the Mediterranean Sea during the past 25 year

Ocean Science ◽  
2014 ◽  
Vol 10 (1) ◽  
pp. 1-16 ◽  
Author(s):  
A. Schneider ◽  
T. Tanhua ◽  
W. Roether ◽  
R. Steinfeldt
Keyword(s):  
Mediterranean Sea ◽  
Deep Water ◽  
Adriatic Sea ◽  
Western Mediterranean ◽  
Tyrrhenian Sea ◽  
Deep Water Formation ◽  
Technical Problems ◽  
Water Formation ◽  
The Mediterranean ◽  
Transient Tracer

Abstract. Significant changes in the overturning circulation of the Mediterranean Sea has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transition (WMT) during the mid-2000s. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of low ventilation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

scholarly journals Diversity and Distribution of the Dinoflagellates Brachidinium, Asterodinium and Microceratium (Brachidiniales, Dinophyceae) in the open Mediterranean Sea

2011 ◽  
Vol 70 (2) ◽  
pp. 209-214 ◽  
Author(s):  
Fernando Gómez
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Life Stage ◽  
Western Mediterranean ◽  
The South ◽  
Levantine Basin ◽  
First Occurrence ◽  
Local Species ◽  
The Mediterranean ◽  
First Time

Diversity and Distribution of the DinoflagellatesBrachidinium, AsterodiniumandMicroceratium(Brachidiniales, Dinophyceae) in the open Mediterranean SeaBrachidiniacean dinoflagellates have been investigated in the open waters of the Mediterranean Sea, along a transect from the south of France to the south of Cyprus (20 June-18 July 2008).BrachidiniumandKarenia papilionaceaoften co-occurred,B. capitatumpredominating in the surface waters. The highest abundance ofBrachidiniumwere found in the upper 25min the western Mediterranean with amaximum (24 cells L-1) at a depth of 5 m in the Balearic Sea.Asterodinium(up to 4 cells L-1) was recorded below of deep chlorophyll maxima. The genusMicroceratium, only known from the tropical Indo-Pacific region, is reported for the first time in the Mediterranean Sea.Microceratiumwas found below 100min the eastern Mediterranean Sea, with the highest abundance of 8 cells L-1at 125 m depth, in the Levantine Basin. This study also illustrates for the first time specimens under the division ofBrachidiniumandMicroceratium. This first occurrence ofMicroceratiumin the Mediterranean Sea should be considered an indicator of climate warming. However, it should not be considered a non-indigenous taxon.Microceratiumis the ‘tropical morphotype’, the adaptation of a local species (a life stage ofKarenia - Brachidinium - Asterodinium) to the tropical environmental conditions that prevail in summer in the open Mediterranean Sea.

scholarly journals Changes in ventilation of the Mediterranean Sea during the past 25 yr

2013 ◽  
Vol 10 (4) ◽  
pp. 1405-1445 ◽  
Author(s):  
A. Schneider ◽  
T. Tanhua ◽  
W. Roether ◽  
R. Steinfeldt
Keyword(s):  
Mediterranean Sea ◽  
Deep Water ◽  
Adriatic Sea ◽  
Western Mediterranean ◽  
Tyrrhenian Sea ◽  
Deep Water Formation ◽  
Overturning Circulation ◽  
Water Formation ◽  
The Mediterranean ◽  
Transient Tracer

Abstract. The Mediterranean Sea has a fast overturning circulation and the deep water masses are well ventilated in comparison to the deep waters of the world ocean. Significant changes in the overturning circulation has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transit (WMT) near the mid of the decade following. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. This variability is important to understand and to monitor, because ventilation is the main process to propagate surface perturbations, such as uptake of anthropogenic CO2, into the ocean interior. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of stagnation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

scholarly journals Tracers confirm downward mixing of Tyrrhenian Sea upper waters associated with the Eastern Mediterranean Transient

2010 ◽  
Vol 7 (4) ◽  
pp. 1533-1557
Author(s):  
W. Roether ◽  
J. E. Lupton
Keyword(s):  
Deep Water ◽  
Time Scale ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
The Other ◽  
Tyrrhenian Sea ◽  
Convective Mixing ◽  
Deep Waters ◽  
Major Process ◽  
Gibraltar Strait

Abstract. Observations of tritium and 3He in the Tyrrhenian Sea, 1987–2009, confirm the enhanced convective mixing of intermediate waters into the deep waters that has been noted and associated with the Eastern Mediterranean Transient in previous studies. Our evidence for the mixing rests on increasing tracer concentrations in the Tyrrhenian deep waters, accompanied by decreases in the upper waters, which are supplied from the Eastern Mediterranean. The downward transfer is particularly evident between 1987 and 1997. Later on, information partly rests on increasing tritium-3He ages; here we correct the observed 3He for contributions released from the ocean floor. The Tyrrhenian tracer distributions are fully compatible with data upstream of the Sicily Strait and in the Western Mediterranean. The tracer data show that mixing reached to the bottom and confirm a cyclonic nature of the deep water circulation in the Tyrrhenian. They furthermore indicate that horizontal homogenization of the deep waters occurs on a time scale of several years. Various features point to a reduced impact of Western Mediterranean Deep Water (WMDW) in the Tyrrhenian during the enhanced-convection period. This is an important finding because it implies less upward mixing of WMDW, which has been named a major process to enable the WMDW to leave the Mediterranean via the Gibraltar Strait. On the other hand, the TDW outflow for several years represented a major influx of enhanced salinity and density waters into the deep-water range of the Western Mediterranean.

scholarly journals Review Article: Atmospheric conditions inducing extreme precipitation over the Eastern and Western Mediterranean

2015 ◽  
Vol 3 (6) ◽  
pp. 3687-3732 ◽  
Author(s):  
U. Dayan ◽  
K. M. Nissen ◽  
U. Ulbrich
Keyword(s):  
Extreme Precipitation ◽  
Mediterranean Basin ◽  
Heavy Rainfall ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Atmospheric Conditions ◽  
Synoptic Scale ◽  
Extreme Precipitation Events ◽  
The Mediterranean ◽  
The Mediterranean Basin

Abstract. This review discusses published studies of heavy rainfall events over the Mediterranean Basin, combining them in a more general picture of the dynamic and thermodynamic factors and processes producing heavy rain storms. It distinguishes the Western and Eastern Mediterranean in order to point at specific regional peculiarities. The crucial moisture for developing intensive convection over these regions can be originated not only from the adjacent Mediterranean Sea but also from distant upwind sources. Transport from remote sources is usually in the mid-tropospheric layers and associated with specific features and patterns of the larger scale circulations. The synoptic systems (tropical and extra-tropical) accounting for most of the major extreme precipitation events and the coupling of circulation and extreme rainfall patterns are presented. Heavy rainfall over the Mediterranean Basin is caused at times in concert by several atmospheric processes working at different atmospheric scales, such as local convection, upper-level synoptic-scale troughs, and meso-scale convective systems. Under tropical air mass intrusions, convection generated by static instability seems to play a more important role than synoptic-scale vertical motions. Locally, the occurrence of torrential rains and their intensity is dependent on factors such as temperature profiles and implied instability, atmospheric moisture, and lower-level convergence.

scholarly journals The effect of cyclones crossing the Mediterranean region on sea level anomalies at the Mediterranean Sea coast

2019 ◽  
Author(s):  
Piero Lionello ◽  
Dario Conte ◽  
Marco Reale
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
Eastern Mediterranean ◽  
Storm Track ◽  
Western Mediterranean ◽  
Residual Water ◽  
Positive Anomaly ◽  
Western Basin ◽  
Sea Level Anomalies ◽  
The Mediterranean

Abstract. Large positive and negative sea level anomalies at the coast of the Mediterranean Sea are linked to intensity and position of cyclones moving along the Mediterranean storm track, with dynamics involving different factors. This analysis is based on a model hindcast and considers nine coastal stations, which are representative of sea level anomalies with different magnitude and characteristics. When a shallow water fetch is present, the wind around the cyclone center is the main cause of sea level positive and negative anomalies, depending on its onshore or offshore direction. The inverse barometer effect produces a positive anomaly at the coast near the cyclone pressure minimum and a negative anomaly at the opposite side of the Mediterranean Sea, because a cross-basin mean sea level pressure gradient is associated to the presence of a cyclone. Further, at some stations, negative sea level anomalies are reinforced by a residual water mass redistribution within the basin, which is associated with a transient response to the atmospheric pressure forcing. Though the link between presence of a cyclone in the Mediterranean has comparable importance for positive and negative anomalies, the relation between cyclone position and intensity is stronger for the magnitude of positive events. Area of cyclogenesis, track of the central minimum and position at the time of the event differ depending on the location where the sea level anomaly occurs and on its sign. The western Mediterranean is the main cyclogenesis area for both positive and negative anomalies, overall. Atlantic cyclones mainly produce positive sea level anomalies in the western basin. At the easternmost stations, positive anomalies are caused by Cyclogenesis in the Eastern Mediterranean. North Africa cyclogeneses are a major source of positive anomalies at the central African coast and negative anomalies at the eastern Mediterranean and North Aegean coast.

Quantification of Bioerosion by Sphaerechinus Granularis on ‘Coralugène’ Concretions of the Western Mediterranean

1997 ◽  
Vol 77 (2) ◽  
pp. 565-568 ◽  
Author(s):  
Stephane Sartoretto ◽  
Patrice Francour
Keyword(s):  
Shallow Water ◽  
Small Diameter ◽  
Western Mediterranean ◽  
Biological Agent ◽  
High Abundance ◽  
Shallow Waters ◽  
Mean Diameter ◽  
The Mean ◽  
The Mediterranean

Sphaerechinus granularis (Echinodermata: Echinidea) is involved in the erosion of ‘coralligène’ concretions in the Mediterranean. In shallow water (10 m), a high abundance of this species (>20 ind 25 m−2) is associated with small diameter individuals (56·7 ±7·7 mm). In deep clean waters (>40 m), the abundance is lower (<1 ind 25 m−2) and the mean diameter is higher (86·0±9·3 mm). Daily erosion of Corallinaceae by this species is related to the urchin diameter (r=0.87). Local variations in urchin abundance and diameter influence the amount of CaCO3 eroded annually. In shallow waters, the eroded CaCO3 mass reaches 210 g m−2 y−1 vs 16 g m−2 y−1 in coralligène concretions in deep clean waters. Sphaerechinus granularis is an important biological agent which substantially erodes the Mediterranean coralligène concretions.

Seasonal ecosystem vulnerability to climatic anomalies in the Mediterranean

2021 ◽  
Author(s):  
Johannes Vogel
Keyword(s):  
Soil Moisture ◽  
Mediterranean Basin ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Ecosystem Productivity ◽  
Data Set ◽  
Ecosystem Vulnerability ◽  
Dry Conditions ◽  
The Mediterranean ◽  
The Mediterranean Basin

&lt;p&gt;The ecosystems of the Mediterranean Basin are particularly prone to climate change and related alterations in climatic anomalies. The seasonal timing of climatic anomalies is crucial for the assessment of the corresponding ecosystem impacts; however, the incorporation of seasonality is neglected in many studies. We quantify ecosystem vulnerability by investigating deviations of the climatic drivers temperature and soil moisture during phases of low ecosystem productivity for each month of the year over the period 1999 &amp;#8211; 2019. The fraction of absorbed photosynthetically active radiation (FAPAR) is used as a proxy for ecosystem productivity. Air temperature is obtained from the reanalysis data set ERA5 Land and soil moisture and FAPAR satellite products are retrieved from ESA CCI and Copernicus Global Land Service, respectively. Our results show that Mediterranean ecosystems are vulnerable to three soil moisture regimes during the course of the year. A phase of vulnerability to hot and dry conditions during late spring to midsummer is followed by a period of vulnerability to cold and dry conditions in autumn. The third phase is characterized by cold and wet conditions coinciding with low ecosystem productivity in winter and early spring. These phases illustrate well the shift between a soil moisture-limited regime in summer and an energy-limited regime in winter in the Mediterranean Basin. Notably, the vulnerability to hot and dry conditions during the course of the year is prolonged by several months in the Eastern Mediterranean compared to the Western Mediterranean. Our approach facilitates a better understanding of ecosystem vulnerability at certain stages during the year and is easily transferable to other study areas and ecoclimatological variables.&lt;/p&gt;

scholarly journals Review Article: Atmospheric conditions inducing extreme precipitation over the eastern and western Mediterranean

2015 ◽  
Vol 15 (11) ◽  
pp. 2525-2544 ◽  
Author(s):  
U. Dayan ◽  
K. Nissen ◽  
U. Ulbrich
Keyword(s):  
Extreme Precipitation ◽  
Mediterranean Basin ◽  
Heavy Rainfall ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Atmospheric Conditions ◽  
Synoptic Scale ◽  
Extreme Precipitation Events ◽  
The Mediterranean ◽  
The Mediterranean Basin

Abstract. This review discusses published studies of heavy rainfall events over the Mediterranean Basin, combining them in a more general picture of the dynamic and thermodynamic factors and processes that produce heavy rain storms. It distinguishes the western and eastern Mediterranean in order to point out specific regional peculiarities. The crucial moisture for developing intensive convection over these regions can be originated not only from the adjacent Mediterranean Sea but also from distant upwind sources. Transport from remote sources is usually in the mid-tropospheric layers and associated with specific features and patterns of the larger-scale circulations. The synoptic systems (tropical and extratropical) that account for most of the major extreme precipitation events and the coupling of circulation and extreme rainfall patterns are presented. Heavy rainfall over the Mediterranean Basin is caused at times in concert by several atmospheric processes working at different atmospheric scales, such as local convection, upper synoptic-scale-level troughs, and mesoscale convective systems. Under tropical air-mass intrusions, convection generated by static instability seems to play a more important role than synoptic-scale vertical motions. Locally, the occurrence of torrential rains and their intensity is dependent on factors such as temperature profiles and implied instability, atmospheric moisture, and lower-level convergence.

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