Modes of the Adriatic long-term variability as seen on half-centurial Palagru ž a Sill series

1. Modes of the Adriatic long-term variability as seen on half-centurial Palagruža Sill series Ivica Vilibić, Hrvoje Mihanović, Jadranka Šepić, Natalija Dunić Institute of Oceanography and Fisheries, Split, Croatia, vilibic@izor.hr

2. Papers: Vilibić, I., Matijević, S., Šepić, J., Kušpilić, G., 2012. Changes in the Adriatic oceanographic properties induced by the Eastern Mediterranean Transient. Biogeosciences, 9, 2085-2097. Vilibić, I., Šepić, J., Proust, N., 2013. Weakening of thermohaline circulation in the Adriatic Sea. Climate Research, 55, 217–225. Vilibić, I., Pištalo, D., Šepić, J., 2015. Long-term variability and trends of relative geostrophic currents in the middle Adriatic. Continental Shelf Research, 93, 70-80. Vilibić, I., Čikeš Keč, V., Zorica, B., Šepić, J., Matijević, S., Džoić, T., 2015. Hydrographic conditions driving sardine and anchovy populations in a land-locked sea. Marine Mediterranean Science, in press, doi: 10.12681/mms.1120. Vilibić, I., Mihanović, H., Ivčević, A., Kušpilić, G., Milun, V., 2015. Mapping of oceanographic properties along a middle Adriatic transect by using Self-Organising Maps. Estuarine Coastal and Shelf Science, 163, 84-92. Mihanović, H., Vilibić, I., Dunić, N., Šepić, J., 2015. Mapping of decadal middle Adriatic oceanographic variability and its relation to the BiOS regime. Journal of Geophysical Research, 120, doi: 10.1002/2015JC010725..

3. Palagruža Sill • Data: • Palagruža transect • Stations P1 (528), P2 (529), P3 (216), P4 (206), P5 (199) – number of vertical profiles in brackets • 1952-2010 • temperature, salinity, DO, TIN, HPO42-

4. Vilibić et al. (BG, 2012): variability EMT  A strong footprint of EMT in all physical and chemical parameters

5. Vilibić et al. (BG, 2012): variability  Different TIN/HPO4 ratio during the EMT period indicate different origin of the intermediate water masses in the Adriatic Sea

6. Vilibić et al. (Cli. Res., 2013): trends • Heating of the Adriatic surface layer • Salinity increase, especially close to coasts • Weakening of dense water formation (northern Adriatic) • Lower LIW transport to the Adriatic Vilibić et al., CR, 2013 • Weakening of the Adriatic THC!!!

7. Vilibić et al. (CSR, 2015): model NEMOMED8 RegCM trends  RegCMs do not reproduce weakening of the Adriatic THC

8. Vilibić et al. (MMS, 2015): fisheries  Fluctuations of sardine and anchovy parameters are dependant on fluctuations of the Adriatic hydrography.

9. Mihanović et al. (JGR, 2015): BiOS patterns Application of a novel method, Self-Organizing Maps (SOM), to the Adriatic long-term thermohaline series. Motivation: To objectively map the characteristic thermohaline patterns over the Palagruža Sill. • What is the SOM method: • Objective mapping method based on neural networks • Performs a nonlinear smooth mapping of high-dimensional input data into the elements of a regular, low-dimensional (usually 2D) array. • This procedure enables that similar patterns are mapped onto neighboring regions on the map.

10. Mihanović et al. (JGR, 2015) • The data: • T, S, DO at the Palagruža Sill, 1952-2010 • SOM setup: • batch training algorithm (efficient training) • a 2x3 SOM grid (good compromise between details and graphic presentation) • rectangular lattice structure (preferable for small size SOMs) • linear initialization of unit weights(EOF decomposition and linear interpolation of the first two leading EOFs – saves time with complex data sets) • “ep” neighborhood function (gives the least smoothing to the SOM units)

11. Mihanović et al. (JGR, 2015) • Objectively extracted patterns at the transect • SOM patterns (BMUs) stand for different circulation modes of the Adriatic, reflecting in water mass and primary production dynamics

12. Mihanović et al. (JGR, 2015) • Changing the length of the dataset and the number of stations used does not largely change SOM patterns All data, gaps 1975-2010, without P4 1994-2010, no gaps

13. Mihanović et al. (JGR, 2015) • BiOS is the dominant generator of the Adriatic variability • SOM patterns of the Absolute Dynamic Topography (ADT) in the northern Ionian Sea show a strong resemblance with T-S changes along the Palagruža Sill • Assymetric ADT patternsinthenorthernIonianSea • BiOSreversalsmayberapid (within a year) or slow (2-3 years), resultingin a rapid or a slowchangesinthe Adriatic properties

14. Conclusions, thoughts, perspectives ... • Palagruža Sill is a key and last standing place in the middle and southern Adriatic where basin-wide permanent monitoring of long-term Adriatic changes has been conducted (since 1952). • Other places (Jabuka Pit, Southern Adriatic Pit) have been strongly undersampled in the last two decades • there is no plan B option for the Adriatic ocean climate monitoring, so the monitoring should be maintained in the future!!! • this data is still scientifically underexploited – an opportunity for the future, also through THEMES collaboration JP IOF long-term monitored stations and transects (1952-2015)