1.3.2. Thermohaline and optical properties of the Drvenik-Hvar-Pelješac area

Branka Grbec1(thermohaline), M ira Morović1*(optical), Frano Matić1, Vlado Dadić1, Igor Palandžić2

1-Institute of Oceanography and Fisheries, Split, Croatia2-Hydraulical Institute, Sarajevo, Bosnia and Herzegovina

PR

OF

ILE

A

200

2-20

03

PR

OF

ILE

B

200

2-20

03

PR

OF

ILE

C –

NE

RE

TV

A E

ST

UA

RY

200

2-20

03

July 2006

Strong heating caused sea

temperatures above 26 oC.

Low impact of less saline coastal waters at the surface.

Shallow thermocline, because of the absence of stronger winds.

July

200

6

Strong heating

Low salinity water (salinity < 34) occupied surface layers in the most southward part of the area.

Thermocline depth was fully developed, below 20 m.

Impact of freshwater at the surface lower than in June.

September 2006

Sep

tem

ber

200

6

Conditions during September cruise were stable with more uniform spatial distribution of temperature and salinity with respect to July.

High resolution measurements of downward irradiance and upward radiance at 14 wavelengths from UV to visible light (340; 380; 412; 443; 465; 490; 510; 532; 555; 589; 625; 665; 683; 710); PAR attenuation (400-700nm); fluorescence           

Kd=dln(Ed(z))/dz

Ku=dln(Lu(z))/dz  

KPar= dln(EPar(z))/dz

Processing:1.Determining cast options2.Selection of better cast for each measurement3.Dark callibration4.Calculations

1. Qualitative and quantitative analysis of spectrum

2. Changes with depth

2. Attenuation coefficients for every wavelength and for PAR

3. Amount of light available for photosynthesis   

4. Euphotic zone depth               

5. Optical signature of chlorophyll-like pigments

(for comparison of chlorophyll signature from remote sensing)

6. Estimates of concentration of chlorophyll-like pigments

7. Estimation of optical types

8. Estimation of different optical functions     

Ed PAR %

dept

h (m

)

1 10 1000

10

20

30

40

50

60

70

80

PAR2

PAR5

PAR7

PAR16

PAR18

PAr21

PAR22

PAR23

Ed PAR %

dept

h (m

)

1 10 1000

10

20

30

40

50

60

70

80

PAR2

PAR7

PAR16

PAR18

PAR21

PAR22

PAR23

PAR irradiance (%) relative to the subsurface in July and September

PAR attenuation coefficient (m-1

)de

pth

(m)

0.0 0.1 0.2 0.3 0.4 0.50

10

20

30

40

50

60

70

80

KPARS2

KPARS5

KPARS7

KPARS8

KPARS9

KPARS11

KPARS13

KPARS16

KPARS17

KPARS18

KPARS20

KPARS21

KPARS22

KPARS23

PAR attenuation coefficient (m -1 )

dept

h (m

)

0.0 0.1 0.2 0.3 0.4 0.50

10

20

30

40

50

60

70

80

KPAR2

KPAR5

KPAR7

KPAR8

KPAR9

KPAR11

KPAR12

KPAR13

KPAR15

KPAR16

KPAR17

KPAR18

KPAR20

KPAR21

KPAR22

KPAR23

PAR attenuation coefficients in July and September

12 July 2006 St5

wavelength (nm)

Kd (

m -

1)

0.0

0.2

0.4

0.6

0.8

1.0

300 350 400 450 500 550 600 650 700 750

depth (m)

2

11

21

31

51

71

12 July 2006 St5

wavelength (nm)

Ku (

m -

1)

0.0

0.2

0.4

0.6

0.8

1.0

300 350 400 450 500 550 600 650 700 750

2

11

21

31

51

71

depth (m)

S20 September

0

0.2

0.4

0.6

0.8

1

1.2

1.4

300 400 500 600 700 800

June S20

0

0.2

0.4

0.6

0.8

1

300 400 500 600 700 800

July September

  Figure 10. Estimated concentration of chlorophyll-like pigments in July (left) and September (right).

estimated chlorophyll concentrations (u g m 3)

dept

h (m

)

0.2 2.2 4.2 6.2 8.2 10.20

20

40

60

80

FFCHL S2

FFCHL S5

FFCHL S7

FFCHL S8

FFCHL S9

FFCHL S8

FFCHL S11

FFCHL S16

FFCHL S17

FFCHL S18

FFCHL S20

FFCHL S21

FFCHL S22

FFCHL S23

estimated chlorophyll concentrations (u g m -3)

dept

h (m

)

0.2 2.2 4.2 6.2 8.2 10.20

10

20

30

40

50

60

70

80

FFCHL S2

FFCHL S5

FFCHL S7

FFCHL S8

FFCHL S9

FFCHL S11

FFCHL S12

FFCHL S13

FFCHL S15

FFCHL S16

FFCHL S17

FFCHL S18

FFCHL S20

FFCHL S21

FFCHL S22

FFCHL S23

estimated chlorophyll concentrations (u g m -3)

dept

h (m

)

1 10 1000

10

20

30

40

50

60

70

80

FFCHL S2

FFCHL S5

FFCHL S7

FFCHL S8

FFCHL S9

FFCHL S11

FFCHL S12

FFCHL S13

FFCHL S15

FFCHL S16

FFCHL S17

FFCHL S18

FFCHL S20

FFCHL S21

FFCHL S22

FFCHL S23

Estimates of chlorophyll-like pigments concentrations for July and September 2006

In September, relative to July, the stations close to Klek-Neum Bay, in the surface 10meters, have for the order of magnitude higher estimates of chlorophyll

Chlorophyll from MODIS for July and September AVHRR temperature

According to water characterisation by Matić (2004), the three characteristic sub-regions can be distinguished:

1. Neretva River estuary (St11-St23) - surface layer of permanently low salinity but spatially and temporally changeable under local meteorological conditions;

2. channel waters (St01-St03, St07-St08) – low salinity surface water influenced by the three main rivers: Neretva, Cetina and Jadro; and

3. waters similar to the open sea (St04-St06) without considerable influence from river runoff and vertically well mixed in the cold period of year.

Stations from waters similar to the open sea have different spectrum characteristics from stations of the Neretva river estuary (Klek-Neum area); spectrum max intensity for estuary area is shifted towards longer wavelengths.

Higher attenuation coefficients (for PAR and wavelengths) in September than in July especially in the Klek-Neum area

Higher chlorophyll-like pigments concentrations estimated for September especially at the surface for most stations, than for July, especially in the Klek-Neum area

Optical characteristics are related to thermohaline characterisation

Concluding remarks