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

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

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

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

Interannual variations C A BiOS phases A substantial interannual variability

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

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

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

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

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)

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

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

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

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?