poster: p2210 09 - control of mangrove abundance by decadal changes in oceanic wave fields
TRANSCRIPT
We found that changes in mangrove extent covary with the North Atlantic Oscillation winter index
1960 1965 1970 1975 1980 1985 1990 1995 2000−3
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400NAO winter indexWave heights PC1 (Expl. var. = 73%) Mangrove PC1 (Expl. var. = 75%)
Expl. covar. (SVD1) = 94.5%
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-0.02
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0.04
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70° 10°20°30°40°50°60°
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Wave heights EOF1 (Expl. var. = 73%)
►The NAO is the dominant mode of climate variability in the North Atlantic-European region. It is characterized by a large-scale seesaw pattern of sea-level pressure anomalies between the Azores High and Icelandic Low (bottom right hand corner).
►The North Atlantic trade winds are strongly coupled to the winter NAO, which leads to strengthening (weakening) wave heights during positive-NAO (negative-NAO) phases.
► Increased (decreased) wave heights favour mangrove shoreline landward (seaward) retreat (expansion).
HS NAO MS
Walcker, R., Anthony, E. J., Cassou, C., Aller, R. C., Gardel, A., Proisy, C., Martinez, J-M. & Fromard, F. (in press) Fluctuations in the extent of mangroves driven by multi-decadal changes in North Atlantic waves. Journal of Biogeography.
Mangroves are uprooted by waves
1950 20141975
We mapped changes in mangrove extent using archival remote sensing images from 1950 to 2014 in French Guiana
40
50
1950 1960 1970 1980 1990 2000 2010
Total mangrove extent (ha×10³)60
Mangrove extent
Spot cnes 2010/09/2710 km SPOT 28/02/2009
Wave exposed zoneMud bank
Amazon turbid plume
Mangrove extent
Amazone estuary
Mud bank (>340Mt)
754 Mt.an−1
150 Mt.an−1
Atlantic ocean
Brazil
Guyana
Suriname
Venezuela
FrenchGuiana
Amazon turbid plume
Amazon sediment dispersal system
We studied the natural 300-km-open coast mangrove system of French Guiana (South America)
Control of mangrove abundance by decadal changes in oceanic wave �eldsRomain Walcker, François Fromard
EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement) UMR 5245 (CNRS, UPS, INP), 118 route de Narbonne, 31062 Toulouse, [email protected] & [email protected]
► The North Atlantic Oscillation (NAO) controls mangrove forest expansion and retreat in French Guiana (South America).► This mechanism operates through wave pounding, which alters the mud substrates on which mangroves thrive.► Wave pounding increases (decreases) during positive (negative) phases of the NAO.► Over the 65 last years in French Guiana, mean winter wave heights fluctuated between 1.6m and 2.2m, leading to changes in mangrove extent of ± 15 000 ha.
Our Common Future Under Climate Change - International Scienti�c Conference 7-10 July 2015 Paris, France