1. Long-term trends and variability in thermohaline properties of the northern Adriatic
Ivica Vilibić1, Petra Zemunik1, Natalija Dunić1, Oussama Marzouk2, Jadranka Šepić1, Hrvoje Mihanović1, Clea Denamiel1, Robert Precali3, Tamara Djakovac3
1 Institute of Oceanography and Fisheries, Split, Croatia
2 student at SeaTech, University of Toulon, Toulon, France
3 CMR, Rudjer Bošković Institute, Rovinj, Croatia
Outline:
Motivation and the data
Seasonal cycle, variability and trends
Correlation to environmental parameters
Take-home messages

2. Deep convection site (AdDW)
Motivation
SAG
EAC
WAC
rivers
Vilibić et al., DSR, 2004
Deep convection site (AdDW)
EAC
Northern Adriatic area is a key area for the Adriatic thermohaline circulation:
Large river inflow
Dense-water formation site

3. The data
Temperature and salinity data collected between 1979 and 2016 at the Po-Rovinj transect
The best sampled is the Nb line, 6 stations (from Croatia to Italy): RV001, SJ107, SJ105, SJ103 SJ101, SJ108
Between 22 and 37 samples per month at Nb line
SJ108
RV001

4. Seasonal cycle
The most of the temperature variance comes from seasonal changes
Low salinity seasonality in deep layers (> 5%), higher at surface
Seasonality in density comes from temperature

5. Interannual variationsC A
BiOS phases
A substantial interannual variability

6. Trends Strong warming, particularly in front of the Po River
Salinity trends are mostly insignificant, aside changes off the Po River
Density trends are dominantly temperature-driven

7. Trends The largest temperature trends in spring-summer
Seasonal changes in density trends are thermally- and haline-driven in the eastern and haline-driven in the western section of the transect

8. Trends
Temperature trends are not sensitive to the series length, in contrast to salinity trends

9. Correlations with drivers
NHF – monthly ECMWF net heat flux averaged over the northern Adriatic
February temperature correlated with December/January NHF, importance of preconditioning

10. Correlations with drivers
PO – monthly Po River discharge
The Po River preconditioning is more important for salinity changes off Po (July-August and November-February)

11. Correlations with drivers
TP – monthly ECMWF total precipitation averaged over the northern Adriatic
Precipitation is not the (direct) driver of the thermohaline changes in the northern Adriatic

12. Correlations with drivers
BiOS – SSH difference between centre and perimeter of the Northern Ionian Gyre
The Adriatic-Ionian Bimodal Oscillating System (BiOS) is marginally influencing the northern Adriatic salinity off Croatian coast at periods up to 1 year

13. Correlations with drivers
yearly scale
Among all regional indices, MOI (Mediterranean Oscillation Index) has the largest correlation to temperature and salinity, then EA and SCA, while NAO and EAWR are not correlated, but ...
The strongest connection is found between salinity and the BiOS at periods between 2 and 4 years

14. Take-home messages
Strong and persistent warming in the northernmost part of the Mediterranean in the last 40 years
Warming is the largest in spring-summer, following the air temperature trends
Salinity trends are a low; a change in the Po River plume dynamics occurred
Heat fluxes are shaping thermohaline properties at scales up to a few months,
River-driven freshening is acting at scales of months, up to a year,
Remote processes, i.e. the BiOS, is acting at processes up to a few years,
Consequences to the ecosystem and fisheries?