Ocean front maps for integrating dynamic thermal, colour and salinity features Peter Miller and Weidong Xu

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1 Ocean front maps for integrating dynamic thermal, colour and salinity features Peter Miller and Weidong Xu 44 th International Liège Colloquium on Ocean Dynamics: Remote sensing of colour, temperature and salinity 7 11 May 2012

2 Ocean fronts for integrating dynamic features Detecting ocean fronts using EO data. Front distribution maps for time-series analysis. Dynamic front animations. Integration of thermal and colour fronts, salinity and height, using GoogleEarth. Acknowledgements:

3 Satellite detection of oceanic fronts 26 Jun :37 27 Jun :58

4 Composite front maps: revealing strong fronts X X F mean F persist F comp Mean gradient P front F prox Persistence Advection / proximity Miller, P.I., (2009) Composite front maps for improved visibility of dynamic oceanic fronts on cloudy AVHRR and SeaWiFS data, Journal of Marine Systems.

5 Advantages of front detection SST F comp Does not blur dynamic features. Highlights persistent or strong gradient fronts. Miller, P.I., (2009) Composite front maps for improved visibility of dynamic oceanic fronts on cloudy AVHRR and SeaWiFS data, Journal of Marine Systems.

6 Thermal composite front map animation. Daily-rolling 7-day maps. Apr-May 2008.

7 Ocean fronts for dynamic oceanography Assist site selection for offshore engineering, minimising impact on marine animals. Provide additional information on surface physical oceanography, from 30 year satellite time-series. May reveal if there is more eddy activity at particular locations or times of year, or predictable seasonal changes in the width of a dynamic current. Integrate with current meters / ADCP, which give velocities at depth but limited regions and time span. Visualise spatial and temporal context of strong current events, and monitor in near-real time. Validation of physical models in terms of frontal locations.

8 Seasonal frequent front maps % Percentage of time for which a strong front was observed, over 10 years Fronts may be used as a proxy for pelagic biodiversity Technology used by Defra to help define Marine Protected Areas Techniques can be applied worldwide Miller, P.I. & Christodoulou, S. (accepted) Frequent locations of ocean fronts as an indicator of pelagic diversity: application to marine protected areas and renewables. Marine Policy. PML Summer

9 Ocean fronts: from spaghetti to synoptic chart Weak Strong May 2008 Key Warm Cold May 2008 Miller, P.I., (in preparation), A line clustering algorithm with application to simplifying ocean front maps derived from satellite data, Remote Sensing of Environment.

10 Merged microwave and infrared SST Weak Strong C Key Warm Cold Daily merged microwave/infrared SST: 24 Oct Composite front map Jul Global synoptic front chart Oct PML Remote Sensing Group Miller, P.I., (in preparation), Global oceanic front charts from automated analysis of merged microwave/infrared SST data.

11 N Atlantic front animation 2008 Rolling 7-day composite front maps derived from OI SST 9km, 01 Jan. 31 Dec PML

12 Chlorophyll-a front maps Monthly median chl-a Monthly chl-a front map Monthly chl-a front chart Sep Sep Sep Daily Aqua- MODIS Chl-a Monthly thermal front chart Sep. 2009

13 Global chlorophyll front map Derived from Aqua-MODIS chl-a data at 4km daily resolution.

14 SMOS Salinity data SMOS salinity data, L3 monthly from 2010, 0.25º, from CATDS Jan Sea-surface salinity: 31 psu 40 psu

15 Sea-surface height data Mean sea-level anomaly (MSLA), monthly for 2010, at 1/3º resolution Mercator projection, from AVISO. Jan SSH: -40 cm +40 cm

16 Compare thermal and colour fronts with salinity Tropical instability waves, higher salinity bounded by thermal and colour fronts. South Pacific high salinity tongue delineated only by colour density not thermal front? Pacific Ocean May 2010 PML 31 psu Salinity 40 psu

17 Compare thermal and colour fronts with SSH Close agreement between SSH and thermal front on meanders of Kurishiro current. Colocation of some thermal and colour fronts; many others are decoupled. Pacific Ocean Jan PML -40 cm SSH +40 cm

18 Integration of fronts, salinity, height GoogleEarth Demonstration PML

19 Ocean fronts for integrating dynamic features Composite front map Frequent fronts Synoptic front chart Integration Global front map Peter Miller,

20 Conclusions on fronts for integration Synoptic front chart highlights important features in ocean temperature and colour data, as discrete entities. Front contours derived from EO thermal and colour data can be combined in GoogleEarth to explore biophysical interactions. Ocean colour may reveal additional physical processes even if there is no thermal signal. Combined visualisations of ocean fronts, SSS and SSH will assist in interpretation and fusion of these datasets. Future work Statistical comparison of thermal/colour fronts, SSS, SSH. Pelagic conservation project with Dukes University/GOBI. Salinity fronts? SSH gradients? Peter Miller - pim@pml.ac.uk