1. No category

OSCAHR
Observing Submesoscale Coupling At High Resolution
A.M. Doglioli, G.Grégori, J.-M. André, N.Barrier, L.Bellomo, L.Berline, F.Carlotti, V.Cornet-Barthaux, A.Costa, F.d'Ovidio, F.Diaz, M.Dugenne,
C.Estournel, O.Grosso, S.Helias-Nunige, K.Leblanc, A.Lefebvre, D.Lefevre, D.Malengros, P.Marsaleix, T.Moutin, F.Nencioli, D.Nerini, I.Pairaud,
A.Petrenko, C.Pinazo, E.Pulido, B.Quéguiner, O.Ross, G.Rougier, S.Schintu-Jacquet, I.Taupier-Letage, M.Thyssen, T.Wagener, B.Zakardjian.
Motivations – Open questions
Infrared
color
Submesoscale dynamics is a key factor in regulating biogeochemical and ecological processes. e.g.
­ Vertical velocity generates strong nutrient injections (Lévy et al., 2012). ­ Stabilisation after the winter period of maximal mixing and grazing relaxation allow phytoplankton to bloom (Chiswell 2011, Taylor and Ferrari 2011 vs Behrenfeld 2010)
Satellite images show the presence of a rich organization of small scale structures between mesoscale eddies : the submesoscale
From Klein et Lapeyre 2009
Origines :
Large­scale impact on primary production and contribution to the global biogeo­
chemical cycles.
Stirring induced by mesoscale → frontogenesis → steep density gradients
→ strong three­dimensional ageostrophic circulations :
The ecological response can rapidly propagate to the higher trophic levels (Cotté et al., 2011).
­ intense vertical velocities (e.g. Klein and Lapeyre, 2009)
­ instabilities attempting to restore the stratication in the upper mixed layer (e.g. Fox­Kemper et al., 2008)
­ local microstructure turbulence (forward energy cascade, e.g. Molemaker et al., 2010).
Impact on community competition and ecosystem distribution is considered a key aspect for the ecological conservation and management of marine resources (Cury et al., 2008).
From Klein et Lapeyre 2009
(adapted from Dickey et al., 2003)
Approaches - Challenges
Our approach : Lagrangian & adaptive strategy with innovative instrumentation
In the last decade, submesoscale dynamics has been predominatly investigated through the analysis of numerical models. (e.g. Capet et al.08)
Submesoscale parametrizations have been proposed for eddy­
resolving (B)OGCM
CytoSense and CytoPro
MVP
Modellers generally highlight the need of in situ measurements
Modellers generally highlight the need of in situ measurements at at submesoscale :
submesoscale :
MVP
a big challenge due to the ephemeral character of these structures.
Lagrangian Navigation
a big challenge due to the ephemeral character of these structures! MVP
pompe
(hydology & plankton)
Lagrangian navigation
à soufflet
(to follow the structures)
SCAMP
(microturbulence)
SCAMP High Frequency Water Pumping The OSCAHR cruise
1­8 novembre 2015 with the R/V Téthys II
+ ANTARES 42 50N 6 10E
TRANSECTS
SHORT STATIONS
Horizontal submesoscale
Vertical Microscale
●
Hull-mounted ADCP
●
SCAMP profiles 0-100m
●
Thermosalinograph & fluorescence
●
LOPC and LISST profiles 0-100m
●
MVP (CTD+Fluo+LOPC)
●
Water Pumping (0-30 m) for :
●
Automated Flow Cytometry
- Conventional Flow Cytometry
●
Surface Nutrients measumermets
- Microphytoplankton microscopy
- Nutrients
+
PLUS
CODE drifters
REMOTE SENSING (Satellite & HF Radar)
OPERATIONAL NUMERICAL MODELLING
Expected results : the cruise will provide a original set of multidisciplinary data on physical­biogeochemical coupling in the costal ocean at submesoscale
and it will allow to test and setup a new sampling strategy for future major campaings
References
P. Klein and G. Lapeyre. The Oceanic Vertical Pump Induced by Mesoscale and Submesoscale Turbulence. Ann. Rev. Mar. Sci., 1:351375, 2009.
B. Fox-Kemper, R. Ferrari, and R. Hallberg. Parameterization of Mixed Layer Eddies. Part I: Theory and Diagnosis. J. Phys. Oceanogr.,
38(6):1145-1165, 2008.
M. J. Molemaker, J. C. McWilliams, and X. Capet. Balanced and unbalanced routes to dissipation in an equilibrated Eady flow. Journal of
Fluid Mechanics, 654:35-63, 2010.
M. Lévy, R. Ferrari, P. J. S. Franks, A. P. Martin, and P. Rivière. Bringing physics to life at the submesoscale. Geophys. Res. Lett.,
39(14):L14602, 2012.
Chiswell SM (2011) Annual cycles and spring blooms in phytoplankton: don’t abandon Sverdrup completely. Mar Ecol Prog Ser 443:39-50
J. R. Taylor and R. Ferrari. On the equilibration of a symmetrically unstable front via a secondary shear instability. Journal of Fluid
Mechanics, 622:103-113, 2009.
Michael J. Behrenfeld 2010. Abandoning Sverdrup's Critical Depth Hypothesis on phytoplankton blooms. Ecology 91:977–989.
C. Cotté, F. d'Ovidio, A. Chaigneau, M. Lévy, I. Taupier Letage, B. Mate, and C. Guinet. Scale-dependent interactions of Mediterranean
whales with marine dynamics. Limnol. Oceanogr., 106(20):219-232, 2011
P. M. Cury, Y.-J. Shin, B. Planque, J. M. Durant, J.-M. Fromentin, S. Kramer Schadt, N. C. Stenseth, M. Travers, and V. Grimm.
Ecosystem oceanography for global change in fisheries. Trends Ecol Evol, 23(6):338-346, 2008.
X. Capet, J. C. McWilliams, M. J. Molemaker, and A. F. Shchepetkin. Mesoscale to Submesoscale Transition in the California Current
System. Part I: Flow Structure, Eddy Flux, and Observational Tests. J. Phys. Oceanogr., 38(1):29-43, 2008.