DATE2018-05-20 12:29:39
AUTHORSA Cascella (1), S Bonomo (2,3), MA Sicré (4), D Insinga (2), P Petrosino (5), N Pelosi (2), S Schmidt (6), B Jalali (7), F Lirer (2)
  1. Istituto Nazionale di Geofisica e Vulcanologia, Pisa, Italy
  2. Istituto per l’Ambiente Marino Costiero, Napoli, Italy
  3. IBM Alberto Monroy, CNR, , Palermo, Italy
  4. Sorbonne Universités /UPMC/ CNRS-IRD-MNHN, Paris, France
  5. Dipartimento di Scienze della Terra, Università degli Studi Federico II. Napoli, Italy
  6. UMR5805 EPOC, Université de Bordeaux, Pessac, France
  7. GEOGLOB, Université de Sfax, Faculté des Sciences, Sfax, Tunisia
ABSTRACTThe high-resolution study of calcareous nannofossils from the sediment core SW104-ND14Q, recovered at 1013m water depth, furnished new information on paleoenvironmental conditions over past 2700 years in the Southern Adriatic Sea. Changes in the abundance of the main surface eutrophic species Emiliania huxleyi and the deep dweller taxa Florishaera profunda were used to reconstruct the phases of stratification/vertical mixing of the upper water column and the associated changes in productivity (Bown et al., 2009). We evaluated the relation of these changes with the climatic and atmospheric conditions acting at local and regional scale (i.e. North Atlantic Oscillation, NAO), and the possible role played by the Bimodal Oscillating System (BiOS) mechanism of Ionian circulation (Civitarese et al., 2010). Reworked coccolith abundance trend were used to reconstruct runoff/precipitation oscillations. The higher productivity values occurred during periods of negative NAO likely coupled with cyclonic phase of BiOS. The inflow of salty and nutrient- rich Levantine Intermediate Water, coupled with the growth of the strength of the South Adriatic Gyre and a stronger positive vorticity wind patterns (Shabrang et al., 2015), favour the deep vertical convection, sustaining a more well defined upper mixed layer that facilitated the flourishing of E. huxleyi. The relative drops in productivity occurred in periods of positive NAO and possible anticyclonic phase of BiOS. This may be related to the advection of less salty and nutrient- rich Modified Atlantic Water which together with the lower positive or slightly negative wind vorticity, weakens deep winter convection and shifts the primary productivity in the deep layers of photic zone favouring the increase of F. profunda relative to other Coccolithophores. The correspondence of reworked coccolith abundance trend with the flood frequency of Southern Alps would confirm that they may be used to reconstruct large scale runoff/precipitation oscillations. This research was carried out in the ambit of Italian Project of Strategic Interest NEXTDATA ( “A national system for recovery, storage, accessibility and dissemination of environmental and climatic data from mountain and marine areas” and of ERC Consolidator Grant (Project ID: 68323 ) “TIMED” Testing the role of Mediterranean thermohaline circulation as a sensor of transient climate events and shaker of North Atlantic Circulation. Bown, P. R., Dunkley Jones, T., Young_ J. R., and Randell, R., 2009. Palaeontology, Vol. 52, Part 2, 2009, pp. 457–469. Civitarese, G., Gačić, M., Lipizer, M. and Eusebi Borzelli, G. L., 2010. Biogeosciences, 7, 3987–3997. Shabrang, L., Menna, M., Pizzi, C. , Lavigne,H., Civitarese,G. and Gačić, M., 2015. Ocean Sci., 12, 233–241.