Year-long measurement of surface currents in the Malta-Sicily Channel:
Lessons learned and implications
Malta, August 29th, 2013
Simone CosoliIstituto Nazionale di Oceanografia e Geofisica Sperimentale, Trieste
Year-long measurement of surface currents in the Malta-Sicily Channel:
Lessons learned and implications
Malta, August 29th, 2013
Simone CosoliIstituto Nazionale di Oceanografia e Geofisica Sperimentale, Trieste
Motivations-1: Marine traffic in the Malta – Sicily Channel
Oil spill density map (source: Policy research Corporation,JJoint Research Centre, European
Commission: http://serac.jrc.it
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Motivations-2: Fishing activities in the Malta – Sicily Channel
(1) Direzione generale delle politiche interne dell’unione Unita’ tematica B Politiche strutturali e di coesione – Pesca: la pesca in Sicilia – Parlamento Europeo
(2) GENERAL FISHERIES COMMISSION FOR THE MEDITERRANEAN
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Some numbers and facts(1,2):
-greatest fishing fleet in Italy as for :- number of boats (3323 boats - 24.4% national fleet @2010), - size of boats (19.3 tons avg – 14tons avg in Italy) - boat power (86.6 KW avg – 83.8 avg in Italy)
-fishing fleet:- 12-24m boats operating on a short-distance basis
(1 to 2 days trips)- >24m boats employed on long fishing trips
(3–4 weeks) in offshore waters
Motivations-2: Fishing activities in the Malta – Sicily Channel
Some numbers and facts(1,2):
-43 301 tons of captures in 2008:- 69% pelagic fishes: small-sized
big-sized
- 10% mollusc
- 21% crustacean
large amount of targeted species and over-fishing problems(1) Direzione generale delle politiche interne dell’unione Unita’ tematica B Politiche strutturali e di coesione – Pesca: la pesca in Sicilia – Parlamento Europeo(2) GENERAL FISHERIES COMMISSION FOR THE MEDITERRANEAN
Engraulis encrasicolus Sardina pilchardus
Xiphias gladius
Thunnus thynnus
Todarodes sagittatus Sepia officinalis
Parapenaeus longirostris Aristeus antennatus Nephrops norvegicus
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Motivations (yes, more): currents – ocean structures impact fish distribution and fishing activity
A conceptual model for Sardine in the Sicily Channel
(*)Lafuente et al., Influence of the surface circulation in the spawning strategy of the Sicilian Channel anchovy, ICES 2000 Annual Science Conference
Remote Ocean Sensing Workshop ROS 2013 March 13 – 14, 2013
Engraulis encrasicolus
Modification in AIS path: along-shore
transport of fish-larvae (depletion and
enrichment)
Offshore advection from AIS branches – upwelling or
northern winds – ageostrophic processesincrease mortality risks
Larvae entrapment in persistent vortices favors
fish growth
Background
ABV = Adventure Bank VortexMCC = Maltese Channel CrestISV = Ionian Shelfbreak Vortex
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Background
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Background
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Drifter tracks in the Sicily Channel (1992 – 2010)
Why not simple buoys?
Problems: Sub-optimal temporal and
spatial coverage in certain areas – oversampling in other areasCALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Why not models?Circulation Models:
3-D momentum eqtn.
continuity eqtn.
eqtn. of state
Problems:Complicated set of Differential Equations – not easy to solve
Tuning required – not always possible die to lack of data
Cannot account for ALL processes: Parametrisation of fine-scale physical processes often needed
No matter what or how complicated one makes it….some process will be missing (always)…
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
Combned TX-RX element
2 orthogonal crossed-loops
>180˚ coverage
combined TX-RX antennaintegrated in the support
mast
Why HF radars?
Italy
Compact, non invasive systems
Safe for population (avg.TX Pw. 35W)
Working continuously independently of weather conditions and sea-state
Unique spatial-temporal high-resolution not achievable with conventional instrumentation
CALYPSO Project Final Meeting, August 29, 2013, University of Malta, Valletta Campus, Valletta
TunisiaAlgeria
Libya
Sicily
Grecia
Albania
France
Italy
HF radar coverage
HF radar maps: how do they look like?
Seasonal variability in the AI-Stream as for position and extension Persistent gyre moves and stretches in time, predominant in winter
August 2012September 2012October 2012
Surface current regimes in the Malta Channel
December 2012
Persistent channel-wide cyclonic gyre (R~30 km) and less-evident anti-cyclonic gyre (R~10 km): impacts DEPEND on release location
16-12-2012
18-01-2013 20-02-2013
Persistent channel-wide cyclonic gyre (R~30 km) and less-evident anti-cyclonic gyre (R~10 km): impacts DEPEND on release location
Persistent channel-wide cyclonic gyre (R~30 km) and less-evident anti-cyclonic gyre (R~10 km): impacts DEPEND on release location
Importance for SAR activities
Importance for spill tracking
Periodic increase of NF levels @13MHz Strongest activity at afternoon-night
Lasting several hours
Affecting 1st order Bragg region interferences with radar currentsCommon problem @13MHz HF radar in the Med.Sea
RFI – removal algorithms exist – actually testing some @OGS
Filtering? Identification required first
ITU rules: HF radars can exist, but with a secondary license --license
Theoretical Noise Level (~-130dBm)
Up to 20-30 dBm fluctuations due to ?
Importance of measuring reliable current data: periodic RFI issue
Thanks for your attention!
Importance for SAR activities