VERTICAL DISTRIBUTION OF PLANKTON IN THE MIXED LAYER, TURBULENCE AND CLIMATE CHANGE

Transcription

1 VERTICAL DISTRIBUTION OF PLANKTON IN THE MIXED LAYER, TURBULENCE AND CLIMATE CHANGE Macías, D. (1,2), Ramírez Romero, E. (3),Rodríguez, A. (4), García, C.M. (3),Bruno, M. (5) (1) Scripps Institution of Oceanography (2) ICMAN CSIC. Cádiz (3) Biology Department. University of Cádiz (4) Physics Department. University of Las Palmas (5) Applied Physics Department. University of Cádiz

2 Summary : 1 Plankton turbulence interactions Theory 1.2 Empirical data (particles turbulence and sedimentation speed) 1.3 Field data (vertical structure and turbulence field) 2 Climate change scenario Theoretical considerations 2.2 Modelling simulations D. Macías et al.

3 1 Plankton turbulence interactions 1.1 Theory Kolmogorov scale (app. 0.1 cms) (Kolmogorov, 1941) Ozmidov scale (app. 100 cms) (Franks, 2005)

4 1 Plankton turbulence interactions 1.1 Theory (Kolmogorov scale) Kolmogorov eddies represent fluid motion at the scale most relevant to microbial dynamics: Biological rates Photosynthesis ( Lewis et al., 1984; Belyaev, 1992) Nutrient uptake ( Lazier & Mann, 1989; Karp Boss et al., 1996) Grazing and encounter rates ( Rothschild & Osborn, 1988; Kiorboe, 1997) Communitycomposition ( Margalefet et al.,1979) Particle

5 1 Plankton turbulence interactions 1.1 Theory (Kolmogorov scale) Vertical structure Diffusion rates Particles swept away from high vorticity regions ( intermittent effect ) Plankton vertical velocity Could this be altered by the turbulent motion? As turbulence at small scales is an isotropic movement, the vertical velocity of a falling particle should not be affected by this motion

6 1 Plankton turbulence interactions 1.1 Theory (Kolmogorov scale) Vertical structure (Wang & Maxey (1993) model) In this structure there are preferential

7 1 Plankton turbulence interactions 1.2 Empirical data (particles turbulence and sedimentation speed) (Zhou & Cheng, 2009) Only one study was made with natural plankton particles and using different methods for generate turbulence (oscillating grids and Couette) and for measure velocities (optic devices and doppler) (Ruiz, Macias & Peters, PNAS, 2004) D. Macías et al.

8 1 Plankton turbulence interactions 1.2 Empirical data (particles turbulence and sedimentation speed) (Ruiz, Macias & Peters, PNAS, 2004) Heavy particles should follows the downward region within the flow

9 1 Plankton turbulence interactions 1.3 Field data (vertical structure and turbulence field) TurboMAP: A free falling micro turbulence profiler equipped with fluorescence probe (i (simultaneous measurements of TKE and fluorescence) Hypothesis to be tested: t That turbulence could change the (Macias et al.,

10 1 Plankton turbulence interactions 1.3 Field data (vertical structure and turbulence field) Modifications of the vertical velocity of the cells DCM position (m) Alboran Sea Strait of Gibraltar Antartic r 2 =0.872 p=1.064e-019 There is usually a relationship between regions of continuous decrease of turbulence and the position of the DCM 20 DCM(m)=1.0071*Tb_gradient(m) End of turbulence gradient (m) 1,0 The magnitude (relative) of the accumulation (DCM)is related with the size (in vertical) of the turbulence gradient % relative accu mulation 0,8 0,6 0,4 0,2 r 2 =0.49; p=1.47e -05 Alboran Sea Strait of Gibraltar Antarctic 0, Size of turbulence gradient(m) D. Macías et al.

11 Summary : 1 Plankton turbulence interactions Theory 1.2 Empirical data (particles turbulence and sedimentation speed) 1.3 Field data (vertical structure and turbulence field) 2 Climate change scenario Theoretical considerations 2.2 Modelling simulations D. Macías et al.

12 2 Climate change scenario 2.1 Theoretical considerations Two main consequences of climate change on the surface ocean: 1. Increase in stratification due to higher SST deeper ML and larger thermoclines (Manabe et al., 1991; Manabe and Stouffer, 1993; Sarmiento et al., 1998; Boop et al., 2001) The most accepted effect of CC is to decrease the vertical flux of particles due to reduced dmixing ii and lower PP levelsl 2. Increase in wind forcing : Intensification of general circulation patterns (Hoskins &Valdes, 1990; Yin, 2005; Toggeweiler & Russell, 2008) D. Macías et al. More frequent and intense storms (Carnell et al., 1996; Cubasch et al., 1997; Ulbrich & Christoph, 1999) Better mixed MLandlarger turbulence gradients

13 2 Climate change scenario 2.1 Theoretical considerations Two main consequences of climate change on (Vilchis the & Balance, surface submitted) ocean: 1. Increase in stratification due to higher SST deeper ML and larger thermoclines (Manabe et al., 1991; Manabe and Stouffer, 1993; Sarmiento et al., 1998; Boop et al., 2001) The most accepted effect of CC is to decrease the vertical flux of particles due to reduced dmixing ii and lower PP levels l 2. Increase in wind forcing : D. Macías et al. Intensification of general circulation patterns More frequent and intense storms (Carnell et al., 1996; Cubasch et al., 1997; Ulbrich & Christoph, 1999) better mixed ML and larger turbulence gradients

14 2 Climate change scenario 2.1 Theoretical considerations (Deeper thermoclines and stronger mixed upper layer) Tb. gr radient Actual conditions ρ,tke,cla. DCM MLD Tb. gradien nt Future scenario ρ,tke,cla. DCM MLD

15 2 Climate change scenario 2.1 Modelling simulations 1D (vertical) model of N P interactions: C React Advect ion D

16 2 Climate change scenario 2.1 Modelling simulations 1D (vertical) model of N P interactions:

17 2 Climate change scenario 2.1 Modelling simulations 1D (vertical) model of N P interactions: Vs =variable

18 2 Climate change scenario 2.1 Modelling simulations 1D (vertical) model of N P interactions: The position of the DCM is correlated with the position of the Vs gradient Alboran Sea Strait of Gibraltar Antartic r 2 =0.872 p=1.064e-019 DCM position (m) 60 40

19 2 Climate change scenario 2.1 Modelling simulations 1D (vertical) model of N P interactions: (Ruiz, Macias & Peters, PNAS, 2004) D. Macías et al.

20 2 Climate change scenario 2.1 Modelling simulations 1D (vertical) model of N P interactions: Large cells Actual C.C. Small cells (Ruiz, Macias & Peters, PNAS, 2004) Actual C.C. +31% +42% Downwards_flux= Vs*C(h,t) (Ruiz et al., 1996) D. Macías et al.

21 CONCLUSIONS: Vertical distribution ib ti of planktonic organisms is influenced by turbulence levels Accumulation of sinking cells happen below the turbulence gradients A warmer and better mixed surface ocean will lead to deeper and larger DCMs This could enhance the vertical flux of organic particles even under the scenario of reduced PP forced by the enhanced stratification Plankton community composition could also be affected by the change in the depth where DCMs are going to be found Turbulence effect on vertical distribution should be included in models for predicting future scenarios of ocean particles fluxes D. Macías et al.

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