Extreme winter 2012 in the Adriatic: an example of climatic effect on the BiOS rhythm

Gačić, Miroslav; Civitarese, Giuseppe; Kovačević, Vedrana; Ursella, Laura; Bensi, Manuel; Menna, Milena; Cardín, Vanessa; Poulain, Pierre-Marie; Cosoli, Simone; Notarstefano, Giulio; Pizzi, C.

doi:10.5194/os-10-513-2014

Cited by 85 publications

(125 citation statements)

References 24 publications

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“…In the cyclonic pattern (Fig. 3a), the depth of the isopycnal 28.9 kg m −3 ranges between 40 and 120 m north of 37 • N. South of 37 • N, a steep gradient, implying isopycnal southward deepening, is observed consistently with the position of the mid-Ionian jet, which is reinforced during the cyclonic regime of the NIG (Bessieres et al, 2013;Gačić et al, 2014). The shallowest isopycnals are located around 39 • N and 18 • E, offshore of the Italian coast, representing the center of the cyclone.…”

Section: Physical and Chemical Characterization Of The Nigmentioning

confidence: 69%

“…It has been demonstrated that this algorithm overestimates by a factor close to 2 [Chl a] in oligotrophic conditions ([Chl a] < 0.4 mg m −3 ) and alternative algorithms have been developed for the Mediterranean Sea (Bricaud et al, 2002;Volpe et al, 2007 The SSALTO-Duacs delayed-time maps of the absolute dynamic topography (ADT) (Rio et al, 2007) for the Mediterranean Sea (1/8 • ) computed and distributed by AVISO (http://www.aviso.altimetry.fr/, last access: January 2016) were downloaded for the period 1993-2014. As proposed by Gačić et al (2014), the sea level gradient between the north and the center of the NIG was used to determine the cyclonic-anticyclonic nature of the NIG circulation. In practice, the ADT difference between rectangles S2 (18.75-19.25 • E and 39.5-40 • N; see Fig.…”

Section: Satellite and Modeling Datamentioning

confidence: 99%

“…1b and c). Variations in horizontal circulation patterns have been detected mainly from altimetric measurements, while the vertical structure of the Ionian circulation has been inferred only recently using float and oceanographic campaign data (Gačić et al, 2014). It has been shown that the Ionian behaves as a two-layer fluid and that the decadal inversions of the NIG are generated by the spreading of the dense water formed in the Adriatic (AdDW).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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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 regimes affect both 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 distribution of isopycnals is provided, and a depth difference of about 80 m is estimated for the nitracline between the 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 onset and the date of maximum chlorophyll were affected by circulation patterns in the north Ionian. In the center of the north Ionian gyre, the bloom started in December and chlorophyll was low in March 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 explaining the interannual variability in bloom onset and intensity. Two trophic regimes were then identified in the north Ionian gyre (NIG) and they could be explained with the relative position of the MLD and nitracline.The first one is characterized by an early winter bloom onset and the absence of a chlorophyll peak in March. It was observed when circulation was anticyclonic or when winter MLD was relatively shallow. Dominant regenerated production all year and an absence of significant nutrient supplies to surface waters are proposed to explain this trophic regime. Conversely, the second trophic regime is marked by a bloom onset in late winter (i.e., February) and a chlorophyll peak in March. The chlorophyll increase was interpreted as a direct response to the nutrient enrichment of surface waters. This winter-spring bloom was observed when circulation was cyclonic and when winter mixing was relatively strong.

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Section: Physical and Chemical Characterization Of The Nigmentioning

confidence: 69%

Section: Satellite and Modeling Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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“…Following Aegean activation, the mode 2 type circulation was re-established. The AIS eastward flow was restored, the upper thermocline salinities in the eastern part of the EMed decreased after 2010, and the upper Ionian Sea circulation in 2011 reversed once more to cyclonic [Gačić et al,2014] What is the role of the atmosphere during these events? To address these questions, we investigate the long-term atmospheric forcing variability and its influence on the thermohaline functioning of the Aegean Sea.…”

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

confidence: 99%

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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“…AW intrusion into the Levantine basin is very variable and may depend on the circulation present in the Ionian (Gačić et al, 2010). In 2011 the NIG circulation was just reversing to cyclonic, as reported in Gačić et al (2014). Previously, the main effect of ∼ 5 years of anticyclonic NIG (2006NIG ( -2010, when the AW meandered in the northernmost part of the Ionian Sea, was a general increase in salinity in the Levantine basin (see the long-term analysis and discussion in Sect.…”

Section: Thermohaline Conditionsmentioning

confidence: 83%

Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?

et al. 2015

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Abstract. Temperature, salinity and oxygen data collected during April and June 2011 (M84/3 and P414 cruises respectively) are analysed to derive the oceanographic characteristics of the Eastern Mediterranean (EM) basin. These observed characteristics are compared with those from previous cruises over the period 1987-2011. As a result, the interannual and decadal variability of the EM thermohaline properties are discussed in the context of the evolution of the Eastern Mediterranean Transient (EMT) and of the general circulation of the basin. We found that the state of the EM is still far from the pre-EMT conditions, though the 2011 results possibly indicate a slow return to this status. In particular, a comparison between thermohaline property evolution deriving from interannual variability of the preconditioning and air-sea interaction (heat fluxes) in the South Adriatic and the Cretan Seas reveals aspects of the alternation of the two dense water sources (Adriatic and Aegean) during the last three decades, which have strong implications for the hydrographic characteristics of the intermediate and deep layers of the Ionian and Levantine basins.

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Extreme winter 2012 in the Adriatic: an example of climatic effect on the BiOS rhythm

Cited by 85 publications

References 24 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

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

Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?

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