Seasonal thermohaline fluctuations in the middle Adriatic Sea

Salinity and temperature time series were analysed for the open sea stations at the transect Split-Gargano, in the middle Adriatic, for the period 1961-1980. Thermohaline fluctuations were described in terms of the principal component scores and, in addition, were compared to heat and water flux at the atmosphere-sea interface. Temperature and salinity vertical gradients in the surface layer are well related to surface fluxes during the whole year. In deeper layers this influence is visible only under the vertically homogenous conditions. Vertical fluxes of heat and salt, compared to the rate of change of the heat and salt content, point to the season with important advection effects. Vertical exchange prevails in the cold season, while horizontal exchange is considerable in the warm period

Long-term changes in hydrographic conditions in northern Adriatic and its relationship to hydrological and atmospheric processes

A very long data series (1921–2000) of hydrographic parameters (temperature, salinity and density) collected in surface and bottom layers at a station in the coastal zone in the northeastern Adriatic was analyzed. Seasonal and interannual variability of the three parameters is described on the basis of monthly and yearly averages. The seasonal cycles obtained were found to be typical for the northern Adriatic. Interannual analysis showed that there was no trend in temperature, salinity and density in the region during the interval analyzed. The long-term series of yearly means of hydrographic parameters were related to the long-term series of yearly means of several hydrological/atmospheric parameters using different time lags of between 0 and 4 years. These parameters are surface heat flux gained by insolation Qs computed for Trieste, precipitation P in Trieste, Po River discharge rate R and two atmospheric oscillation indexes, a Mediterranean Oscillation (MO) index and North Atlantic Oscillation (NAO) index. At zero time lag the interannual changes at the surface were found to be significantly related to changes in the Qs and NAO index (temperature) and R (salinity and density). At the same time lag the changes in the bottom were found to be related to the MO index (temperature, salinity and density). Additionally, bottom salinity and density were significantly related to R at a time lag of 1 year.<br><br> <b>Key words.</b> Oceanography: Physical (air-sea interactions; hydrography

First record of small tropical calanoid copepod Parvocalanus crassirostris (Copepoda, Calanoida, Paracalanidae) in the Adriatic Sea

In December 2014 the adult females and copepodites of alien paracalanid copepod Parvocalanus crassirostris were identified in the Central Adriatic port of Šibenik. The most probable transmission vector for this small copepod were ballast waters from the cargo ships that are regularly discharged at these locations. This paper is focused on P. crassirostris morphology and the state of population in the port of Šibenik. The possible path of introduction of Parvocalanus crassirostris into the Adriatic Sea is also discussed

Bora-induced currents corresponding to different synoptic conditions above the Adriatic

International audienceThe Bora wind field is characterised by strong vorticity and divergence. Several numerical experiments, in which an oceanographic model was forced with northeasterly winds having climatological alongshore variability, were performed in order to study the influence of spatial variability in the bora wind field on the surface currents in the northern Adriatic. Numerical model results showed that during bora episodes with lower speeds and fast offshore decay surface currents along transect Rovinj - Po River are predominantly in the downwind direction. On the other hand, during bora episodes with strong intensity and slow offshore decay, a cyclonic gyre due to the pronounced bora alongshore variability is formed in the northernmost part of the Adriatic Sea and the studied transect is influenced by the counter currents. Moreover, bora having a high speed and a short offshore range produces the same effect in the eastern part of the Rovinj - Po River transect as low-speed bora characterised by slow offshore decay. Eulerian current measurements performed in the northern Adriatic during bora episodes characterised by different synoptic conditions supported the numerical model findings. Surface currents during the bora episode of 8-11 February 1984 were directed downwind, whereas during the episode of 12-19 February 1984 they were directed upwind. The first episode was characterised by a deep bora layer with cyclonic activity over the western Mediterranean and Genoa Bay, whereas the second one was accompanied by temperature inversion and a southwesterly tropospheric wind above a shallow bora layer. According to the hydraulic theory developed by Smith (1985), an observed descent of isentropes during the second bora episode led to the stronger acceleration in the bora layer and its larger offshore extent. Different offshore bora decays during studied events were confirmed by a comparison of the wind data originating from the meteorological stations positioned on the opposite Adriatic coasts

Response of the Adriatic Sea to the atmospheric anomaly in 2003

Unusual weather conditions over the southern Europe and the Mediterranean area in 2003 significantly impacted the oceanographic properties of the Adriatic Sea. To document these changes, both in the atmosphere and the sea, anomalies from the normal climate were calculated. The winter 2003 was extremely cold, whereas the spring/summer period was extremely warm. The air temperature in June was more than 3 standard deviations above the average. On the other hand, precipitation and river runoff were extremely low between February and August. The response of the sea was remarkable, especially in surface salinity during spring and summer, with values at least one standard deviation above the average. Analysis of thermohaline properties in the middle Adriatic showed the importance of two phenomena responsible for the occurrence of exceptionally high salinity: (1) enhanced inflow of saline Levantine Intermediate Water (LIW) in the Adriatic, and (2) extremely low precipitation and river runoff, accompanied with strong evaporation. Two large-scale atmospheric indices: NAOI (North Atlantic Oscillation Index) and MOI (Mediterranean Oscillation Index), although generally correlated to the Adriatic climate, failed to describe anomalies in 2003. The air pressure gradients used for the definition of both indices significantly decreased in 2003 due to the presence of the high pressure areas over most of Europe and the northern Atlantic, and were actually responsible for the observed anomalies above and in the Adriatic

Analysis of phytoplankton community in the vicinity of domestic sewage outflow during stratified conditions

The response of phytoplankton community structure to anthropogenically-derived nutrient from the submarine sewage outflow was analysed in a shallow coastal area of the middle Adriatic Sea. The study was conducted during the eight-year period (2002-2010) at six stations in the Brač Channel, aiming to assess the potential change in the state of biological and environmental parameters before and after the sewage commissioning. The research was particularly focused on phytoplankton producers during the summer which is considered to be critical due to water stratification and low water dynamics. The results show an increase in phytoplankton biomass in the deep layer after the discharge activation that was significant (M-W test; U=584.5, p<0.01), but not related to any intense phytoplankton bloom or oxygen deficiency. Temporal variability of total phytoplankton abundances throughout the research period indicated a significant increase in 2005, the year following the sewage outflow activation. Pairwise Dunn's multiple comparison test emphasised the difference in the years before the sewage activation (2002, 2003) compared to 2005 (2002 vs. 2005, R=-60.92 p<0.001; 2003 vs. 2005, R=-63.92 p<0.001). This situation was soon followed by the rapid equalization in phytoplankton abundances. Considering the entire research period, there were no changes in contributions of major phytoplankton groups, but the increase in overall species diversity was recorded, supporting the view that moderate inputs may stimulate plankton taxonomic diversity in coastal ecosystems. Increased ciliate and copepod nauplii abundance was also observed but was considered to be caused by natural variability

A 55-Year Time Series Station for Primary Production in the Adriatic Sea: Data Correction, Extraction of Photosynthesis Parameters and Regime Shifts

In 1962, a series of in situ primary production measurements began in the Adriatic Sea, at a station near the island of Vis. To this day, over 55 years of monthly measurements through the photic zone have been accumulated, including close to 3000 production measurements at different depths. The measurements are conducted over a six-hour period around noon, and the average production rate extrapolated linearly over day length to calculate daily production. Here, a non-linear primary production model is used to correct these estimates for potential overestimation of daily production due to linear extrapolation. The assimilation numbers are recovered from the measured production profiles and subsequently used to model production at depth. Using the recovered parameters, the model explained 87% of variability in measured normalized production at depth. The model is then used to calculate daily production at depth, and it is observed to give on average 20% lower daily production at depth than the estimates based on linear extrapolation. Subsequently, water column production is calculated, and here, the model predicted on average 26% lower water column production. With the recovered parameters and the known magnitude of the overestimation, the time-series of water column production is then re-established with the non-linearly-corrected data. During this 55-year period, distinct regimes were observed, which were classified with a regime shift detection method. It is then demonstrated how the recovered parameters can be used in a remote sensing application. A seasonal cycle of the recovered assimilation number is constructed along with the seasonal cycle of remotely-sensed chlorophyll. The two are then used to model the seasonal cycle of water column production. An upper and a lower bound on the seasonal cycle of water column production based on remotely-sensed chlorophyll data are then presented. Measured water column production was found to be well within the range of remotely-sensed estimates. With this work, the utility of in situ measurements as a means of providing information on the assimilation number is presented and its application as a reference for remote sensing models highlighted

Izvješće Hrvatskog odbora za geodeziju i geofiziku o provedenim aktivnostima od 2019. do 2022. - podneseno Generalnoj skupštini Međunarodne unije za geodeziju i geofiziku, Berlin, Njemačka, 2023.

Content: Introduction Geodesy in Croatia, 2019–2022 Geomagnetism and aeronomy in Croatia, 2019–2022 Hydrology and physical limnology in Croatia, 2019–2022 Meteorology in Croatia, 2019–2022 Physical oceanography in Croatia, 2019–2022 Seismology in Croatia, 2019–2022Sadržaj: Uvod Geodezija u Hrvatskoj, 2019.–2022 Geomagnetizam i aeronomija u Hrvatskoj, 2019.–2022 Hidrologija i fizikalna limnologija u Hrvatskoj, 2019.–2022 Meteorologija u Hrvatskoj, 2019.–2022 Fizička oceanografija u Hrvatskoj, 2019.–2022 Seizmologija u Hrvatskoj, 2019.–202