An Internal Mechanism Driving the Alternation of the Eastern Mediterranean Dense/Deep Water Sources

Theocharis, Alexander; Krokos, George; Velaoras, Dimitris; Κορρές, Γεράσιμος

doi:10.1002/9781118847572.ch8

Cited by 48 publications

(78 citation statements)

References 62 publications

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“…These reversals are related to the spatial variability of the meandering AIS along with the respective reduction or restoration of the LIW/CIW flow in the North Ionian. The thermohaline pump mechanism proposed by Theocharis et al, [2014] differs from the BiOS mechanism proposed by Gačić et al [2010Gačić et al [ , 2011 Krokos et al [2014] showed that this pumping mechanism is an ongoing internal mechanism that led to the reactivation of the Aegean Sea during 2007-2009 almost a decade after the end of the EMT production period. Both Theocharis et al, [2014] and Krokos et al [2014] argue that the role of the internal mechanism seems to prevail over the long-term atmospheric influence in DWF events in the EMed.…”

Section: Deep Water In the Cretan Sea And The Eastern Mediterranean Tmentioning

confidence: 49%

“…These events are the result of salinity preconditioning in the eastern part of the EMed, i.e. the Aegean and Levantine Seas, which according to Theocharis et al, [2014] is mostly attributed to an internal oscillating thermohaline pump mechanism that affects the upper thermohaline conveyor belt of the EMed.…”

Section: Discussionmentioning

confidence: 99%

“…Data before 1986 -1987 in the EMed exist only from bottle casts at standard depth levels which makes the investigation on the existence of dCIW rather difficult. Nevertheless, several papers [Lascaratos et al, 1999;Theocharis et al, 2002b;Skliris and Lascaratos, 2004;Skliris et al, 2007;Beuvier et al, 2010;Vervatis et al, 2013;Theocharis et al, 2014] based on both observations and numerical modeling have reported a similar event taking place in the eastern part of the EMed during the 1970s. This event was salinity induced and seems to have originated through dense water formation taking place in the Aegean and/or Levantine Seas during a salinity preconditioning phase.…”

Section: Events Of Dciw Outflow and ''Emt-like'' Episodes And Their Rmentioning

confidence: 99%

“…The role of these almost decadal oscillations has been presented in Theocharis et al [2014] and Krokos et al [2014]. According to the mechanism proposed by these authors, DWF triggered by winter cooling in each active DWF subbasin (i.e., the Adriatic or the Aegean Seas) causes the outflow of dense water through the deepest layers of the straits of each active subbasin which is balanced by inflow from the upper layers.…”

Section: Events Of Dciw Outflow and ''Emt-like'' Episodes And Their Rmentioning

confidence: 99%

“…Conversely, anticyclonic upper Ionian circulation favors winter convection in the Aegean/Levantine Seas, while AW flowing into the Adriatic makes it more buoyant. Theocharis et al [2014] using numerical simulation and in situ data for the period 1960-2000 have shown the existence of a rather permanent almost decadal anticorrelated oscillation between the Adriatic and the Aegean Seas which act competitively as Dense Water Formation (DWF) sources. The authors proposed that the two DWF sources' antagonistic functioning is controlled by an internal thermohaline pump mechanism.…”

Section: Deep Water In the Cretan Sea And The Eastern Mediterranean Tmentioning

confidence: 99%

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Dense intermediate water outflow from the Cretan Sea: A salinity driven, recurrent phenomenon, connected to thermohaline circulation changes

et al. 2014

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Data collected from different platforms in the Cretan Sea during the 2000s decade present evidence of gradually increasing salinity in the intermediate and deep intermediate layers after the middle of the decade. The observed gradual salt transport toward the deeper layers indicates contributions of dense water masses formed in various Aegean Sea subbasins. The accumulation of these saline and dense water masses in the Cretan Sea finally led to outflow from both Cretan Straits, with density greater than typical Levantine/Cretan Intermediate water but not dense enough to penetrate into the deep layers of the Eastern Mediterranean. We name this outflowing water mass as dense Cretan Intermediate Water (dCIW). A retrospective analysis of in situ data and literature references during the last four decades shows that similar events have occurred in the past in two occasions: (a) in the 1970s and (b) during the Eastern Mediterranean Transient (EMT) onset (1987)(1988)(1989)(1990)(1991). We argue that these salinity-driven Aegean outflows are mostly attributed to recurrent changes of the Eastern Mediterranean upper thermohaline circulation that create favorable dense water formation conditions in the Aegean Sea through salinity preconditioning. We identify these phenomena as ''EMT-like'' events and argue that in these cases internal thermohaline mechanisms dominate over atmospheric forcing in dense water production. However, intense atmospheric forcing over an already salinity preconditioned basin is indispensable for creating massive deep water outflow from the Cretan Sea, such as the EMT event.

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Section: Deep Water In the Cretan Sea And The Eastern Mediterranean Tmentioning

confidence: 49%

Section: Discussionmentioning

confidence: 99%

Section: Events Of Dciw Outflow and ''Emt-like'' Episodes And Their Rmentioning

confidence: 99%

Section: Events Of Dciw Outflow and ''Emt-like'' Episodes And Their Rmentioning

confidence: 99%

Section: Deep Water In the Cretan Sea And The Eastern Mediterranean Tmentioning

confidence: 99%

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Dense intermediate water outflow from the Cretan Sea: A salinity driven, recurrent phenomenon, connected to thermohaline circulation changes

et al. 2014

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A process study of the Adriatic‐Ionian System baroclinic dynamics

et al. 2016

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The driving mechanisms behind the decadal reversal of the Ionian Sea upper layer circulation recently sparked a considerable discussion in the Mediterranean scientific community. It has been suggested that the reversal can be driven by variations in wind stress curl over the basin, baroclinic dynamics acting within the Adriatic‐Ionian System (AISys) or baroclinic dynamics driven by thermohaline properties at the AISys eastern boundary. Here we perform numerical simulations in order to assess the relative importance of remote forcings (wind stress, thermohaline fluxes, thermohaline open boundary conditions) on the vorticity and energy budget of the Ionian Sea. A mechanistic understanding of the AISys dynamics is achieved with an approach based on an increasing complexity in the model forcings and domain. Our experiments suggest that wind stress does not play a leading role in the vorticity and energy budgets of the Ionian Sea. Wind stress can reinforce or weaken the circulation but it is not able to reverse its sign. Its role becomes dominant only in the absence of inflows through the Antikythira Strait and Cretan Passage. Instead, reversals in the upper layer circulation of the Ionian Sea take place only in the presence of an active boundary on the Aegean Sea/Levantine Basin side and appear to be correlated with substantial exchanges of Availalble Potential Energy between the two basins (as observed at the end of the Eastern Mediterranean Transient). From an energetic point of view, AISys can be explained therefore only if the role of the Aegean Sea is explicitly considered.

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The Response of the Aegean Sea (Eastern Mediterranean) to the Extreme 2016–2017 Winter

Velaoras

Papadopoulos

Kontoyiannis

et al. 2017

Geophysical Research Letters

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The exceptionally cold December 2016 over the Aegean Sea—one of the most important dense water formation areas of the eastern Mediterranean Sea—resulted in winter heat loss comparable to the peak Eastern Mediterranean Transient winters (1992–1993). Hydrological data sampled in March/April 2017 showed that newly produced dense waters ventilated the North Aegean deep basins up to density horizons of σθ ~ 29.35 kg/m3. The water column ventilation was unable to reach the bottom as the present upper thermohaline circulation of the eastern Mediterranean does not favor the salinity preconditioning of the Aegean Sea. In the southwest Aegean, the Myrtoan basin was ventilated by dense waters traceable farther south to the West Cretan Straits. Export of these masses from the Aegean Sea can potentially have a broader impact on the thermohaline circulation of the eastern Mediterranean.

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An Internal Mechanism Driving the Alternation of the Eastern Mediterranean Dense/Deep Water Sources

Cited by 48 publications

References 62 publications

Dense intermediate water outflow from the Cretan Sea: A salinity driven, recurrent phenomenon, connected to thermohaline circulation changes

Dense intermediate water outflow from the Cretan Sea: A salinity driven, recurrent phenomenon, connected to thermohaline circulation changes

A process study of the Adriatic‐Ionian System baroclinic dynamics

The Response of the Aegean Sea (Eastern Mediterranean) to the Extreme 2016–2017 Winter

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