Satellite Derived Dynamic Ocean Currents in the Arctic. Jens Olaf Pepke Pedersen Polar DTU / DTU Space

Transcription

1 Satellite Derived Dynamic Ocean Currents in the Arctic Jens Olaf Pepke Pedersen Polar DTU / DTU Space

2 Benefits of exploiting ocean currents Benjamin Franklins map of the Gulf Stream (1769) 2 Polar DTU, Danmarks Tekniske Universitet

3 Modern oceanography: Challenger expedition of HMS Challenger in St. Thomas Harbor (1876) 3 Polar DTU, Danmarks Tekniske Universitet

4 Ocean currents (1911) 4 Polar DTU, Danmarks Tekniske Universitet

5 Atmospheric circulations Polar DTU, Danmarks Tekniske Universitet

6 Polar DTU, Danmarks Tekniske Universitet Surface currents driven by winds

7 Arctic currents Jeanette attempt to reach North Pole (1879), sinks : wreckage from Jeannette found on an ice floe near Julianehåb (now Qaqortoq) Polar DTU, Danmarks Tekniske Universitet

8 Fram expedition ( ) Nansen Polar DTU, Danmarks Tekniske Universitet The Fram Drift

9 Arctic currents Currents determined by - Dominant winds - Inflow from Pacific Ocean (0.5 m heigth difference at Bering Strait) - Outflow from rivers (2½ x Bering Strait) Polar DTU, Danmarks Tekniske Universitet

10 Early attempt at route optimization Jens Munk ( ) Tries to find a way to India through the North West Passage Spends the winter in Hudson Bay. Only 3 of his 64 men crew returns home. 10 Polar DTU, Danmarks Tekniske Universitet

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15 BlueSIROS SIROS = Satellite Integrated Route Optimisation Service. Near Real Time Marine Route Optimisation Service Integrating Satellite Derived Dynamic Ocean Currents. Funded by ESA Collaboration between DTU Space, DTU Transport, DHI and Danish Defence Centre for Operational Oceanography 9 month Feasibility study Potential users involved: Maersk Marine Technology Norden DFDS Seaways Danish Maritime Authority Surface current map of the North Atlantic 2 year test period Funded by Orients Fond March 4, 2009, northeast Pacific Ocean 15 Polar DTU, Danmarks Tekniske Universitet

16 Study objective Feasibility of an operational system for marine route optimisation, which integrates forecasts of ocean currents based on near-real time satellite altimetry data. Enabling shipping companies to minimize fuel consumption -> reduce air pollution and fuel costs. 15 years of seafaring experience using weather routing: Reduced fuel consumption by 6% Reduced ship rough weather damages by 73% Costs of maintenance by 29 % Cargo damage lawsuits by 87% Length of ship delays due to unfavourable weather by 80% 16 Polar DTU, Danmarks Tekniske Universitet

17 Ocean currents (wind driven) Ekmann spiral Polar DTU, Danmarks Tekniske Universitet

18 Current measurements at sea Polar DTU, Danmarks Tekniske Universitet

19 Current measurements from land Polar DTU, Danmarks Tekniske Universitet

20 Argo floats Comprised of three subsystems: Hydraulics: control buoyancy adjustment via an inflatable external bladder, so the float can surface and dive. Microprocessors: deal with function control and scheduling. Data transmission system: controls communication with satellite. Approx. Weight: 25 Kg Max. operating depth: 2000m Crush depth: 2600m Polar DTU, Danmarks Tekniske Universitet

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22 Argo Deployments began in 2000 and continue today at the rate of about 800 per year Polar DTU, Danmarks Tekniske Universitet

23 Jason & Argo Argonauts on their ship Argo (detail from Athenian red-figure clay vase, BC) Led by Jason they sailed to Colchis on the Black Sea (modern Georgia) and brought back the famous Golden Fleece (detail from Athenian red-figure clay vase, BC) 23 Polar DTU, Danmarks Tekniske Universitet

24 Altimetric Observations 1. Where is the satellite? 2. The distance from the satellite to the ocean. Accurate radar (or laser) ranging to the sea surface based on accurate time-determination d = t * c / 2 c must be adjusted slighly for propagation through ionosphere and troposphere. Sea surface heigth caused by other factors than gravity SSH = Height sat Range Height sat is determined using GPS Polar DTU, Danmarks Tekniske Universitet

25 Corrections Polar DTU, Danmarks Tekniske Universitet

26 Orbit Parameters Coverage of sea surface depends on the orbit parameters (inclination of the orbit plane and repeat period). JASON - 10 Days Satellite Repeat period Track spacing Inclination Sentinel-3 30 days 95 km 98 JASON days 315 km 66.5 Cryosat days 7 km 88 Polar DTU, Danmarks Tekniske Universitet

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28 Ocean currents Satellite altimeter: determines sea surface relative to reference ellipsoid Shape of sea surface -> information on geoid and the ocean circulation Ocean at rest: surface = geoid (+/- 100 m around ellipsoid) Ocean moves: surface deviates from geoid -> information on tides and surface currents The geostrophic balance: 28 Polar DTU, Danmarks Tekniske Universitet

29 Geostrophic Currents 29 Polar DTU, Danmarks Tekniske Universitet

30 Computing surface currents Model formulation combines geostrophic, Ekman shear dynamics, surface buoyancy etc. Ocean eddies - up to about 25 cm Temperature of the upper ocean water - up to about 35 cm Tides in the deep ocean - up to 1 m Ocean currents or ocean circulation up to 2 m Topography (m) Geostrophic currents (m/s) 30 Polar DTU, Danmarks Tekniske Universitet

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32 Using ocean eddies 32 Polar DTU, Danmarks Tekniske Universitet

33 Data + models available: Near real-time estimates of currents, wind speed, and wave height Newly developed vessel drift model for bulk carriers for both deep and shallow waters: predicts the ships behaviour encountering wind, waves and currents (inputs: geometric and operational characteristics of the ship, stability and hydrostatic data, ship position) 33 Polar DTU, Danmarks Tekniske Universitet

34 Data + models available: Near real-time estimates of currents, wind speed, and wave height Integrate in standard ocean modelling and forecasts Estimated savings on trans-atlantic route (average speed of 16 knots): 7.5% when riding favourable currents 4.5% when avoiding unfavourable currents 34 Polar DTU, Danmarks Tekniske Universitet

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36 Challenges in the Arctic Region General metocean data less accurate Safety requirements for maritime traffic in the Arctic are higher (safety of the ship and its crew, and the environment) Defence Centre for Operational Oceanography (DCOO) represents a user with requirements for optimisation of complex operations during adverse conditions such as search and rescue operations. Low inclination of the Jason-2 & -3 orbits ( 66 ) preclude them covering the Arctic oceans. Only European Sentinels will be capable of providing EO information for marine route optimisation in the Arctic Ocean. Communication towards the ships has limited bandwidth, which may restrict the amount of information transmitted. Jason 3 launched 17 January 2016 (Sentinel 3A in Febuary 2016) 36 Polar DTU, Danmarks Tekniske Universitet

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