Satellite observations of SW oceanography in 2013, and using fronts to describe ecological interactions
Peter Miller
South West Marine Ecosystems Conference 2014
4th April 2014
Plymouth Marine Laboratory
Satellite oceanography and fronts
• SW oceanography from space in 2013
• Algal blooms in 2013
• Satellite detection of ocean fronts
• Ecological applications, conservation and MPAs
MultiView composites
2001 vs 2007 vs 2013 SST
°C
Feb
Oct.
Cooler than
usual
Warmer than
usual
Earlier onset of stratification
April 2001 Apr 2013
Miller, P.I. (2009) Composite front maps for improved visibility of dynamic sea-surface features
on cloudy SeaWiFS and AVHRR data. Journal of Marine Systems, 78(3), 327-336.
A “typical” July – amazingly not stormy
Jul 2001 Jul 2013
Later breakdown of stratification
Oct. 2001 Oct. 2013
Chlorophyll-a in a ‘typical’ year
Chlorophyll-a in 2013 – lower than typical?
Longer Spring bloom
Lack of summer
dinoflagellate
blooms
Algal bloom news
• In June 2013, there was an
extensive Phaeocystis bloom
along the south Devon & Cornwall
coast.
• Could this have depleted the
nutrients to reduce later blooms?
• In early 2014, we observed
species normally associated with
warm temperate/tropical water:
• Dinophysis tripos – Toxic
• Trichodesmium – brought by
Gulf Stream
Satellite oceanography and fronts
• SW oceanography from space in 2013
• Algal blooms in 2013
• Satellite detection of ocean fronts
• Ecological applications, conservation and MPAs
Introduction to ocean fronts
• Ocean fronts delineate the
boundary between water masses.
• Analogous to atmospheric fronts.
• Where interesting things happen…
• Areas of enhanced mixing.
• Many pelagic fish and megafauna
distributions are related to fronts.
SST map
Local window
Histogram bimodality
test and threshold
Cohesion test
Cayula, J.-F., and Cornillon, P., (1992), Edge detection algorithm for SST
images. Journal of Atmospheric and Oceanic Technology, 9, 67-80.
Front detection method
Front map
Contour following
Advantages of front detection
SST Fcomp
• 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.
Satellite oceanography and fronts
• SW oceanography from space in 2013
• Algal blooms in 2013
• Satellite detection of ocean fronts
• Ecological applications, conservation and MPAs
Jul. 1982
Frequently observed ocean fronts
Dec.1998
Nov. 2008
• Huge unique archive: >30,000
AVHRR passes 1999-2008
• Developed and tested methodology
to analyse persistent fronts in time
series
• Percentage of months in which strong
front observed = Frequent fronts
%
Summer
Miller, P.I. & Christodoulou, S. (2014) Frequent locations of ocean fronts as an
indicator of pelagic diversity: application to marine protected areas and
renewables. Marine Policy. 45, 318–329.
• Front maps were used to
prioritise candidate MPAs:
10 out of 46 offshore MPAs.
Areas of Pelagic Ecological Importance
%
Summer
Frequent fronts
Warm S
trong
Weak
Cold
Key May
2008 May
2008
Ocean fronts: from spaghetti to synoptic chart
Miller, P.I., (in preparation), A line clustering algorithm with application to simplifying ocean front maps derived from satellite data, Remote Sensing of Environment.
Warm S
trong
Weak
Cold
Key
Low High
Front distance
Low High
Front density
May
2008
Ocean front metrics
May
2008
Front side
Studying marine animal use of fronts
• Gaining evidence on different marine taxa Pirotta, E., et al. (2014) Scale-dependent foraging ecology of a marine top predator modelled using
passive acoustic data. Functional Ecology, 28(1), 206-217.
Oppel, S., et al. (2012) Comparison of five modelling techniques to predict the spatial distribution
and abundance of seabirds. Biological Conservation, 156, 94-104.
Schabetsberger, R., et al. (2013) Oceanic migration behaviour of tropical Pacific eels from Vanuatu.
Marine Ecology Progress Series, 475, 177-190.
Edwards, E.W.J., et al. (2013) Fine-scale linkage between coastally breeding seabirds and mid-
Atlantic Ridge prey communities. Deep Sea Res. II, 98B, 438-444.
• Kylie Scales
– PhD project on ocean front metrics for improving
understanding of marine animal distribution.
Scottish marine protected areas
• Advancing the methodology to
detect fronts closer to the coast
– Ocean colour fronts at 300m resolution
– Compare thermal and colour fronts
• Used to support the development of
Scotland's MPA network
– Identify areas of wider functional
importance
Hot off
the press
www.snh.gov.uk
Miller, P.I., Xu, W. & Carruthers, M. (submitted) Seasonal shelf-sea front mapping using satellite ocean colour
and temperature to support development of a marine protected area network. Deep Sea Research II.
Going global with EBSAs
• In a project with the US Duke University,
we are providing large-scale front frequency
maps to guide definition of Ecologically or
Biologically Significant Areas (EBSAs) in the
high seas. East Pacific
North Pacific NW Atlantic
Workshops to define high-seas MPAs
• Intergovernmental meetings
organised by the Convention on
Biological Diversity.
• The front maps contributed to
East Pacific EBSAs for:
– Costa Rica Dome
– Carnegie Ridge and Equatorial front
Satellite oceanography and fronts
• SW oceanography from space in 2013
• Algal blooms in 2013
• Satellite detection of ocean fronts
• Ecological applications, conservation and MPAs
Peter Miller [email protected]
Extra slides
Thermal and chlorophyll front fusion
Thermal fronts
Dilated 6 pixels Chl-a fronts
Dilated 6 pixels
Front fusion
mask
Front fusion map:
• bright/faded (fusion)
• red/blue (thermal),
• green/blue (chl-a),
• magenta/blue (overlap)
Sep.
2010
Biophysical interactions
• Co-location of many
fronts in March on Malin
Shelf.
• Notice the outer front at
the shelf-break is only a
chl-front - water may be
stratified.
Mar. 2010
Front metrics for marine ecology
Frequent fronts
Global front map
Synoptic front chart
Peter Miller, [email protected]
Composite front map
Fusion / integration
Satellite detection of oceanic fronts
26 Jun.
2009
06:37
27 Jun.
2009
19:58
Composite front maps: revealing strong fronts
Fmean Fcomp
X
Fpersist
X
Pfront Fprox
Miller, P.I., (2009) Composite front maps for improved visibility of dynamic oceanic fronts on cloudy AVHRR and SeaWiFS data, Journal of Marine Systems.
Mean gradient
Persistence Advection / proximity
Basking shark track vs. synoptic fronts
Warm
Str
ong
Weak
Cold
Key
Acknowledgements to Prof David Sims and his shark-tagging team at MBA, Plymouth 24 Aug. – 15 Oct. 2002
Kittiwake foraging radii
Acknowledgements to Natural England; RSPB staff and
volunteers (mainland), Vickie Heaney (Scilly) and Nicola
Saunders and Sophie Wheatley (Lundy).
Kittiwake productivity vs fronts
Fronts and marine biology
• Bakun’s triad: enrichment, concentration and
retention – Bakun (2006) Fronts and eddies as key structures in the
habitat of marine fish larvae. Scientia Marina.
Priede, I.G. & Miller, P.I. (2009) A basking shark tracked by satellite
with simultaneous remote sensing: reveals orientation to a
thermal front. Fisheries Research, 95(2-3), 370-372.
5.5°W 5.0°W
55.5°N
55.0°N
Firth of
Clyde,
Scotlan
d
Basking
shark
track Front
• Many pelagic fish distributions related to fronts – E.g. tuna: Worm et al. (2005)
Global patterns of predator diversity in the open oceans. Science.
– E.g. basking sharks: Fronts influence zooplankton diel migration and hence prey behaviour (Sims et al., 2005).
Front metrics for marine ecology
• Introduction to ocean fronts
• Satellite detection of ocean fronts
• Front metrics and ecological applications
• Nuts and bolts
Matchup input data format
• A text file with space-separated values (can be multiple spaces or
tabs), in these columns in this order (or Excel spreadsheet)
– latitude: decimal degrees, north positive.
– longitude: decimal degrees, east positive.
– value: any numeric value, could be the measurement for that position, or
some numeric sample identifier.
– date: in format dd/mm/yyyy.
– time: in format hh:mm. Use '12:00' if the time is unimportant or unknown.
50.5905 -2.9153 2.394 13/06/2005 12:00
50.6817 -2.9817 1.8967 27/06/2005 12:00
50.6750 -2.9817 0.945 29/06/2005 12:00
50.6613 -2.8433 1.7388 13/07/2005 12:00
50.7008 -2.7535 0.0436 30/04/2007 12:00
50.5667 -3.4200 0.2091 30/01/2008 12:00
50.4500 -3.4700 1.1 09/09/2009 12:00 . . .
Matchup output format
lat lon value EO_value st_dev offset[day] date time match_filename
54.24310 -4.76190 12.11600 -999.00000 0.00000 -999.00000 10/08/2012 14:57 Missing
54.24940 -4.79160 12.11500 -999.00000 0.00000 -999.00000 10/08/2012 10:23 Missing
54.27150 -4.74900 12.11400 -999.00000 0.00000 -999.00000 10/08/2012 07:45 Missing
54.16240 -4.79490 12.11300 0.00300 0.00000 -0.80208 09/08/2012 07:15 M2012218-
54.22490 -4.70270 12.11200 0.00220 0.00000 -1.10417 09/08/2012 14:30 M2012218-
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