UNIVERSITY of ROME “TOR VERGATA”XXV Doctoral Program

A study of the Tiber River dynamics and coastal primary production with satellite data,

circulation and primary production models

Institute of Atmospheric Sciences and Climate of the Italian National Research Council (ISAC-CNR).

Cinzia Pizzi

TIBER PLUME

Motivation

NASA MODIS - Sediment plume from the Tiber River, Italy (http://modis.gsfc.nasa.gov/)

The algal biomass activity is modified from rivers’ load:

POSITIVE EFFECT NEGATIVE EFFECT

TYRRHENIAN SEA

ROME

Rome

Motivation

POSITIVE EFFECT

NUTRIENTS INCREASE

ALGAL PRODUCTIVITY

SUPPORTS

MARINE FOOD WEB

Motivation

NEGATIVE EFFECT

POLLUTANTS(heavy metal, hydrocarb., etc.)

NUTRIENTS SURPLUS

HARMFUL ALGAL BLOOMS

DANGEROUS

• MARINE ECOSYSTEM• TOURISM• FISHING

(www.centroricerchemarine.it)

RED TIDE BLOOM

OBJECTIVES

Development of aCOASTAL MONITORING

TOOLfor the Tyrrhenian Sea

(Tiber river)

• TIBER PLUME DYNAMICS

• TIBER PLUME EFFECT

COASTAL & OFFSHORE AREAS MORE EXPOSED TO THE TIBER LOAD

MODULATION ON PRIMARY PRODUCTION

Rome

Analyzed periods

WINTER CASE STUDY

SUMMER CASE STUDY

DECEMBER 2008

NOVEMBER 2010

TypicalTiber River discharge

(860 m3/s)

Exceptional Tiber River discharge (1660 m3/s) since 1965

Typical Tiber River discharge

(210 m3/s) JULY 2010

Dataset 1) SATELLITE DATASET (MODIS/AQUA)

1. Surface Chlorophyll-a (chl - mg m-3)

2. Diffuse light attenuation coefficient at 490 nm (K490; m-1)

3. Turbid water flag (L2flag – CASE 1 or open sea water & CASE 2 or coastal water)

(December 2008, July and November 2010)

Dataset 2) MODEL DATASET (Dr. Inghilesi, ISPRA runs)

output

output

Lagrangian diffusion particles POM salinity/current fields

1) POM (Princeton Ocean Model) current, temperature, salinity fields

2) Lagrangian model (nested in POM) Trajectory/distribution of synthetic particles released at Tiber estuary

LAM (Limited Area Model) wind to force POM circulation

(December 2008, July and November 2010)

Dataset 3) Wind data

LAM WIND MODEL DATA(POM FORCING)

ASCAT WIND SATELLITE DATA(LAM WIND VALIDATION)

Wind Speed dataset

Interc. Slope MBE(m/s)

RMSE(m/s)

CorrC N. of pair

ASCAT-LAM 2.25 0.78 -0.59 2.48 0.77 41363

Results 1) LAM WIND VALIDATION WITH ASCAT

(December 2008, July and November 2010)

Dataset 4) Primary Production (PP) from VGPNN model (Vertically Generalized Production Neural Network; Scardi, 2001)

Data output:

Primary Production (PP - g C m2 day-1) for the Tyrrhenian Sea

Data input:

SATELLITE DATA (MYOCEAN products):

• Surface chlorophyll (chl - mg m-3)

• Sea Surface Temperature (SST – C°)

• Photosynthetically Available Radiation (PAR - E m-2 day-1)

MODEL DATA (Circulation POM)

• Mixed Layer Depth (MLD)

(December 2008, July and November 2010)

5 Dec.

5 Dec. 30 Dec.

Current & particle distribution (DECEMBER 2008)

Results 2) River plume dynamics

30 Dec.

Sea Surface Temperature (DECEMBER 2008)

19 Dec.

Wind & particle concentration (DECEMBER 2008)

90°

45°

Ekman

Ekm

an

wind

DECEMBER 2008

• Coastal - offshore interaction dynamics IMPORTANT

• Coastal circulation driven by offshore oceanographic features, NOT by wind

• Tiber plume moves northwestwards

25 Nov.5 Nov.

5 Nov. 25 Nov.

Sea Surface Temperature (NOVEMBER 2010)

Current & Particle distribution (NOVEMBER 2010)

Wind & particle concentration (NOVEMBER 2010)

90°

45°

Ekm

an E

kman

wind

Results 2) River plume dynamics

12 Nov.

NOVEMBER 2010

• Coastal - offshore dynamics is• partly coupled to Tyrrhenian Sea

cyclonic eddy (e.g. Nov 25)• partly wind driven (e.g. Nov 5)

• THEREFORE: Tiber plume moves both northwestwards & southeastwards

Current & particle distribution (JULY 2010)

14 Jul. 30 Jul.

Sea Surface Temperature (JULY 2010)

14 Jul. 30 Jul.

Wind & particle concentration (JULY 2010)

24 Jul.

Results 2) River plume dynamics

90°

45°

Ekman

Ekm

an

wind

JULY 2010

• The cold cyclonic gyre is absent

• Wind driven circulation

• Tiber plume moves northwestwards, southeastwards & offshore

• Plume is more mobile because the summer MLD is shallower i.e. plume is thinner.

20 Dec. 20 Dec.20 Dec.

Results 2) River plume dynamics

ModelTiber plume

CHL K490 (water transparency) Tw (coastal and offshore water)

SatelliteTiber plume

20 Dec.

Model/plume circulation well reproduces reality as seen from satellite data

Results 3) Plume effects on primary production

Comparison between Primary production and daily Tiber discharge

S. Marinella – Anzio

PP R T-st. P

Discharge

t- 7 0.72 2.02 0.07

t- 8 0.74 2.03 0.06

time lag=8 days

Results 3) Plume effects on primary production

Algal biomass seems to be favoured by

Tiber river discharge

Results 2) Plume effects on primary production

Particle concentration (Cp) model output

satellite chl (mg m-3)

P. Production PP (g C m-2 day-1)

December 2008

High PP at gyre edge:favored by submesoscale

dynamics (Lévy et al., 2001)

PP R T-st. P

Discharge

t- 3 0.67 2.340 0.04

t- 10 0.57 2.0 0.06

Results 3) Plume effects on primary production

1) Nutrients are not limiting in the control box

Hypotheses on observed summer PP variability

2) Nutrients are limiting in the control box:

NUTRIENTS SUPPLY FROM:

COASTAL UPWELLING

ZOOPLANKTON GRAZING

(TOP - DOWN CONTROL)

SUMMER AGRICULTURALFERTILIZING

Conclusions

WINTER: plume is heavily influenced by offshore structures (Tyrrhenian eddy) basin - wide dynamics important for coastal monitoring

SUMMER: plume is wind mesoscale driven (absence of organized offshore dynamic structures impact in the coast)

Model/plume circulation reasonably well reproduces reality as seen from satellite validation

PRIMARY PRODUCTION: seems more directly connected to winter peak Tiber discharge; summer correlation not likely (to be verified)

FUTURE WORK • Extension to multi-year satellite/model datasets

• Integration with in situ data (ISAC-CNR Tyrrhenian sea 2010- 2013 cruises)

THIS WORK: PROTOTYPE TOOL FOR COASTAL MONITORING

APPLICATIONS: WFD (Water Framework Directive) MFSD (Marine Framework Strategy Directive)

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