Abrupt climate shift in the Western Mediterranean Sea

Schröeder, Katrin; Chiggiato, Jacopo; Bryden, Harry L.; Borghini, Mireno; Ismail, S. Ben

doi:10.1038/srep23009

Cited by 146 publications

(172 citation statements)

References 31 publications

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“…Consistent with the amplification of the global ocean water cycle and salinity mean patterns, the Mediterranean Sea underwent a strong salinification since the 1950s (Rohling and Bryden 1992;Bethoux and Gentili 1999;Rixen et al 2005;Vargas-Yanez et al 2010;Skliris et al 2014b;Borghini et al 2014;Schroeder et al 2016). In particular, below 1000 m depth the Mediterranean basin exhibited the strongest salinity gain in the World Ocean since 1950 (Skliris et al 2014b), whereas the increased salinity signal of the Mediterranean Overflow Water (MOW) is also clearly depicted at intermediate depths (1000-1500 m) in Fig.…”

Section: Introductionmentioning

confidence: 62%

“…In particular, we find largest salinity increases of order 0.015 pss/decade at intermediate/deep layers of the South Aegean Sea linked with the Eastern Mediterranean Transient over the late 1980s/early 1990s (Klein et al 1999;Theocharis et al 1999), and at the bottom layer of the Ligurian-Provencal basin mainly associated with the Western Mediterranean Transient (WMT), a climatic shift started in mid-2000s with several strong deep water formation events abruptly increasing bottom layer salinity (e.g. Schroeder et al 2016). Full-depth volume-averaged salinity change over 1950-2015 in En4 is stronger in WMED (0.079 ± 0.011) than in EMED (0.059 ± 0.013) ( Fig.…”

Section: Surface Freshwater Flux Changesmentioning

confidence: 99%

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Mediterranean sea water budget long-term trend inferred from salinity observations

et al. 2018

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Changes in the Mediterranean water cycle since 1950 are investigated using salinity and reanalysis based air-sea freshwater flux datasets. Salinity observations indicate a strong basin-scale multi-decadal salinification, particularly in the intermediate and deep layers. Evaporation, precipitation and river runoff variations are all shown to contribute to a very strong increase in net evaporation of order 20-30%. While large temporal uncertainties and discrepancies are found between E-P multidecadal trend patterns in the reanalysis datasets, a more robust and spatially coherent structure of multi-decadal change is obtained for the salinity field. Salinity change implies an increase in net evaporation of ~ 8 to 12% over 1950-2010, which is considerably lower than that suggested by air-sea freshwater flux products, but still largely exceeding estimates of global water cycle amplification. A new method based on water mass transformation theory is used to link changes in net evaporation over the Mediterranean Sea with changes in the volumetric distribution of salinity. The water mass transformation distribution in salinity coordinates suggests that the Mediterranean basin salinification is driven by changes in the regional water cycle rather than changes in salt transports at the straits.

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Section: Introductionmentioning

confidence: 62%

Section: Surface Freshwater Flux Changesmentioning

confidence: 99%

Mediterranean sea water budget long-term trend inferred from salinity observations

et al. 2018

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“…Another important portion of the newly formed deep waters could also get trapped inside very coherent submesoscale eddies responsible for their propagation toward the basin interior as shown by Testor andGascard [2003, 2006]. Recent abrupt changes in the WMDW characteristics have been shown to eventually propagate to Gibraltar in about 3 years, subsequently impacting the Mediterranean overflow [Schroeder et al, 2016].…”

Section: Introductionmentioning

confidence: 99%

Scales and dynamics of Submesoscale Coherent Vortices formed by deep convection in the northwestern Mediterranean Sea

et al. 2016

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Since 2010, an intense effort in the collection of in situ observations has been carried out in the northwestern Mediterranean Sea thanks to gliders, profiling floats, regular cruises, and mooring lines. This integrated observing system enabled a year‐to‐year monitoring of the deep waters formation that occurred in the Gulf of Lions area during four consecutive winters (2010–2013). Vortical structures remnant of wintertime deep vertical mixing events were regularly sampled by the different observing platforms. These are Submesoscale Coherent Vortices (SCVs) characterized by a small radius (∼5–8 km), strong depth‐intensified orbital velocities (∼10–20 cm s−1) with often a weak surface signature, high Rossby (∼0.5) and Burger numbers O(0.5–1). Anticyclones transport convected waters resulting from intermediate (∼300 m) to deep (∼2000 m) vertical mixing. Cyclones are characterized by a 500–1000 m thick layer of weakly stratified deep waters (or bottom waters that cascaded from the shelf of the Gulf of Lions in 2012) extending down to the bottom of the ocean at ∼2500 m. The formation of cyclonic eddies seems to be favored by bottom‐reaching convection occurring during the study period or cascading events reaching the abyssal plain. We confirm the prominent role of anticyclonic SCVs and shed light on the important role of cyclonic SCVs in the spreading of a significant amount (∼30%) of the newly formed deep waters away from the winter mixing areas. Since they can survive until the following winter, they can potentially have a great impact on the mixed layer deepening through a local preconditioning effect.

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“…Since the 1950s, the heat and salt content of BW have increased steadily. This increase has heavily intensified since 1985 (Rixen et al, 2005;Krahmann and Schott, 1998 (Schroeder et al, 2016). Within two years, BW ex-perienced an increase in potential temperature and salinity of 0.038 • C and 0.016, respectively (Schroeder et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Hydrography and circulation west of Sardinia in June 2014

Knoll¹,

Borrione

Fiekas³

et al. 2017

Ocean Sci.

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Abstract. In the frame of the REP14-MED sea trial in June 2014, the hydrography and circulation west of Sardinia, observed by means of gliders, shipborne CTD (conductivity, temperature, depth) instruments, towed devices, and vesselmounted ADCPs (acoustic doppler current profilers), are presented and compared with previous knowledge. So far, the circulation is not well-known in this area, and the hydrography is subject to long-term changes. Potential temperature, salinity, and potential density ranges as well as core values of the observed water masses were determined. Modified Atlantic Water (MAW), with potential density anomalies below 28.72 kg m −3 , showed a salinity minimum of 37.93 at 50 dbar. Levantine Intermediate Water (LIW), with a salinity maximum of about 38.70 at 400 dbar, was observed within a range of 28.72<σ /(kg m −3 ) < 29.10. MAW and LIW showed slightly higher salinities than previous investigations. During the trial, LIW covered the whole area from the Sardinian shelf to 7 • 15 E. Only north of 40 • N was it tied to the continental slope. Within the MAW, a cold and saline anticyclonic eddy was observed in the southern trial area. The strongest variability in temperature and salinity appeared around this eddy, and in the southwestern part of the domain, where unusually low saline surface water entered the area towards the end of the experiment. An anticyclonic eddy of Winter Intermediate Water was recorded moving northward at 0.014 m s −1 . Geostrophic currents and water mass transports calculated across zonal and meridional transects showed a good agreement with vessel-mounted ADCP measurements. Within the MAW, northward currents were observed over the shelf and offshore, while a southward transport of about 1.5 Sv occurred over the slope. A net northward transport of 0.38 Sv across the southern transect decreased to zero in the north. Within the LIW, northward transports of 0.6 Sv across the southern transects were mainly observed offshore, and decreased to 0.3 Sv in the north where they were primarily located over the slope. This presentation of the REP14-MED observations helps to further understand the long-term evolution of hydrography and circulation in the Western Mediterranean, where considerable changes occurred after the Eastern Mediterranean Transient and the Western Mediterranean Transition.

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Abrupt climate shift in the Western Mediterranean Sea

Cited by 146 publications

References 31 publications

Mediterranean sea water budget long-term trend inferred from salinity observations

Mediterranean sea water budget long-term trend inferred from salinity observations

Scales and dynamics of Submesoscale Coherent Vortices formed by deep convection in the northwestern Mediterranean Sea

Hydrography and circulation west of Sardinia in June 2014

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