A mixed‐layer study of the formation of Levantine intermediate water

Lascaratos, A.; Williams, Richard G.; Tragou, Elina

doi:10.1029/93jc00912

Cited by 127 publications

(90 citation statements)

References 19 publications

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“…However, in 5 regions where meso-scale circulation is cyclonic (e.g. South Adriatic gyre, Rhodes gyre), there are evidences of surface nutrient enrichment caused by vertical mixing (Gacic et al, 2002;Lascaratos et al, 1993;Salihoglu et al, 1990). Thus, the Eastern Mediterranean Sea likely holds both trophic regimes; one involving subsequent surface nutrients supplies by winter vertical mixing and the other not.…”

Section: Role Of the Nig Circulation Compared To The Interannual Varimentioning

confidence: 99%

Impact of decadal reversals of the North Ionian circulation on phytoplankton phenology

Lavigne¹,

Civitarese²,

Gačić³

et al. 2017

Preprint

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Abstract. In the North Ionian, water circulation is characterized by a decadal alternation of cyclonic and anticyclonic regime driven by the mechanism called BiOS (Bimodal Oscillating System). The circulation regime affects the vertical dynamics and the nutrient distribution. The North Ionian is then a good study area to investigate how changes in circulation can affect phytoplankton dynamics in oligotrophic regions. From in situ observations, for each circulation regime the averaged 15 distribution of isopycnals is provided, and a depth difference of about 80m is estimated for the nitracline between cyclonic and anticyclonic regime. Based on phytoplankton phenology metrics extracted from annual time-series of satellite ocean color data for the period 1998-2012, the cyclonic and anticyclonic regimes are compared. Results show that the average chlorophyll in March, the date of bloom initiation and the date of maximum chlorophyll were affected by circulation patterns in the North Ionian. In the center of the gyre, bloom initiation occurred in December and chlorophyll was low in March 20 when circulation was anticyclonic, whereas during the cyclonic circulation regime, a late chlorophyll peak, likely resulting from different phytoplankton dynamics, was commonly observed in March. An additional analysis shows that the winter buoyancy losses, which govern the Mixed Layer Depth (MLD) also contribute to explain the interannual variability in bloom initiation and intensity. Two scenarios involving the relative position of the MLD and nitracline are finally developed, discussed and tested with model data to explain the different phenology patterns observed in the North Ionian. 25

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Section: Role Of the Nig Circulation Compared To The Interannual Varimentioning

confidence: 99%

Impact of decadal reversals of the North Ionian circulation on phytoplankton phenology

Lavigne¹,

Civitarese²,

Gačić³

et al. 2017

Preprint

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“…The heat loss during winter time in the MAW in the EMed leads to a sufficient increase of density to form the Levantine intermediate water (LIW) at depths between 200 and 600 m (Brasseur et al, 1996;Wuest, 1961). The exact area of the LIW formation process is poorly constrained and possibly variable, but it is expected to be in the eastern part of the EMed near Rhodes (Malanotte-Rizzoli and Hecht, 1988;Lascaratos et al, 1993;Roether et al, 1998). The main volume of the LIW flows back westwards over the shallow sill between Sicily and Tunisia entering the Tyrrhenian Sea along the continental slope of Italy (Wuest, 1961).…”

Section: T Stöven and T Tanhua: Vent Med Constrained By Transientmentioning

confidence: 99%

Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

Stöven

Tanhua

2014

Ocean Sci.

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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 (SF 6 , 3 H and 3 He) 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.

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“…Our objective is to develop a mixed-layer model that can be applied over different parts of the basin by including a parameterized advection; our approach has been applied in the eastern Mediterranean [Lascaratos et al, 1993] and is similar to that used by Battisti et al [1995] for the North Atlantic. The mixed-layer thickness and density are solved for from the density budget (equation (5)) and the turbulent kinetic energy equation of the mixed-layer model [Williams, 1988] using surface density fluxes and winds, together with the parameterization for the geostrophic advection (equation (6)).…”

Section: Convective Nutrient Supply and Export Productionmentioning

confidence: 99%

Estimating the convective supply of nitrate and implied variability in export production over the North Atlantic

Williams¹,

McLaren²,

Follows³

2000

Global Biogeochemical Cycles

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A mixed‐layer study of the formation of Levantine intermediate water

Cited by 127 publications

References 19 publications

Impact of decadal reversals of the North Ionian circulation on phytoplankton phenology

Impact of decadal reversals of the North Ionian circulation on phytoplankton phenology

Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

Estimating the convective supply of nitrate and implied variability in export production over the North Atlantic

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