Recent studies on the Adriatic long-term oceanographic changes

1
Recent studies on the Adriatic long-term
oceanographic changes
Ivica Vilibic Institute of Oceanography and
Fisheries, Split, Croatia, vilibic_at_izor.hr
2
Papers Vilibic, I., Matijevic, S., Šepic, J.,
Kušpilic, G., 2012. Changes in the Adriatic
oceanographic properties induced by the Eastern
Mediterranean Transient. Biogeosciences, 9,
2085-2097. Vilibic, I., Šepic, J., Proust, N.,
2013. Weakening of thermohaline circulation in
the Adriatic Sea. Climate Research, 55,
217225. Vilibic, I., Pištalo, D., Šepic, J.,
2015. Long-term variability and trends of
relative geostrophic currents in the middle
Adriatic. Continental Shelf Research, 93,
70-80. Vilibic, I., Cikeš Kec, V., Zorica, B.,
Šepic, J., Matijevic, S., Džoic, T., 2015.
Hydrographic conditions driving sardine and
anchovy populations in a land-locked sea. Marine
Mediterranean Science, in press, doi
10.12681/mms.1120. Vilibic, I., Mihanovic, H.,
Ivcevic, A., Kušpilic, G., Milun, V., 2015.
Mapping of oceanographic properties along a
middle Adriatic transect by using Self-Organising
Maps. Estuarine Coastal and Shelf Science, in
press. Mihanovic, H., Vilibic, I., Dunic, N.,
Šepic, J., 2015. Mapping of decadal middle
Adriatic oceanographic variability and its
relation to the BiOS regime. Journal of
Geophysical Research, under review.
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
Vilibic et al. (BG, 2012)
EMT
? A strong footprint of EMT in all physical and
chemical parameters
5
Vilibic et al. (BG, 2012)
? Different TIN/HPO4 ratio during the EMT period
indicate different origin of the intermediate
water masses in the Adriatic Sea
6
T, S, st, DO trends 1952-2010 significant at
95 o insignificant
Vilibic et al. (CR, 2013)
Italy
Croatia
? Trends in the last 60 years indicate a
weakening of the Adriatic THC
7
Vilibic et al. (CSR, 2015)
NEMOMED8 RegCM trends
? RegCM do not reproduce weakening of the
Adriatic THC
8
Vilibic et al. (MMS, 2015)
? Fluctuations of sardine and anchovy parameters
are dependant on fluctuations of the Adriatic
hydrography.
9
Mihanovic et al. (JGR, 2015)
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.

• The data
• T, S, DO at the Palagruža Sill, 1952-2010

• SOM setup
• batch training algorithm (efficient training)
• a 4x3 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)

10
Mihanovic et al. (JGR, 2015)

• The data
• T, S, DO at the Palagruža Sill, 1952-2010

11
Mihanovic 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
Mihanovic et al. (JGR, 2015)

• Changing the length of the dataset and the
  number of stations used does not change largely
  SOM patterns
• BIOS is the dominant generator of the Adriatic
  variability

All data, gaps
1975-2010, without P4
1994-2010, no gaps
13
Mihanovic et al. (JGR, 2015)

• SOM patterns of the Absolute Dynamic Topography
  (ADT) in northern Ionian Sea show a strong
  resemblance with T-S changes along the Palagruža
  Sill
• Assymetric ADT patterns in the northern Ionian
  Sea
• BiOS reversals may be rapid (within a year) or
  slow (2-3 years), resulting in a rapid or a slow
  changes in the Adriatic properties

14
Some SCOOL perpectives ...

• Data
• There are other long-term stations which may be
  investigated for long-term changes ? e.g. in
  coastal region coming from Pag-Konavle monitoring
  programme, D1200, ...
• ... to be used for assessment of changes in
  eastern coastal area

• Research topics
• Connecting Adriatic changes to the Ionian
  circulation
• Analysing climate hindcast and projections for
  the Adriatic decadal changes and processes (DWF,
  BiOS)
• Constructing a simple BiOS-based index
• Reconstructing oceanographic conditions from
  chronologies
• Connecting chronologies with long-term data
  measurements