Predictive Understanding of the Oceans' Wind-Driven Circulation on Interdecadal Time Scales

Transcription

1 CCPP Mtg. Seattle, Oct , 2004 Predictive Understanding of the Oceans' Wind-Driven Circulation on Interdecadal Time Scales Michael Ghil Atmospheric & Oceanic Sciences Dept. and IGPP, UCLA Roger Temam Mathematics Dept. and ISCAM, Indiana University Motivation 1. Anthropogenic effects on climate act on a complex system characterized by natural variability on many space and time scales. 2. The ocean s wind-driven & thermohaline circulation exhibit interannual & interdecadal oscillations. 3. We concentrate on the wind-driven circulation, subject to fixed atmospheric forcings as well as coupled to atmospheric variability. Work with H. Dijkstra (CSU), Y. Feliks (IIBR, Israel, & UCLA), K. Ide (UCLA), G. Loeper (U. of Nice, France), E. Simonnet (INLN, France, & UCLA), L. Sushama (UQAM, Canada) & T. Tachim-Medjo (Florida Intl. U.)

2 Outline A. Dynamical results 1. Double-gyre results (ocean only) prescribed wind stress QG, SW & PE models, agreement with 7-yr period in NAO observations periodic wind stress effect on inertial recirculation 2. Effects of oceanic thermal front on atmosphere barotropic baroclinic B. Numerical results (see also poster) 1. High-order approximations for PE models 2. Expansion in the H/L aspect ratio 3. Inertial algorithms for the PEs

3 ! "#$% &'(( ) +*,&-.0/ : ;=<?>A@.BDCFEGIHB JLKNM <O@.PRQ KS;=TOJU8 : KNJWVX<OJLJWKS;=T ;ZY T[<OM B\H]KNV^P@_HB JL<O@QJ Basin size: 2000 x 2000 x 5 km (grid: 14 km, 15 layers) 2 1 Lateral viscosity: 80 m s, Thermal diffusivity: 2 m s density deviation Z=0 Z= 1300 m Z= 2600 m MAX = e+00 MIN = e MAX = e 01 MIN = e MAX = e 03 MIN = e Z= 4000 m MAX = e+00 MIN = e MAX = e 04 MIN = e Z (15 m) MAX = e 01 MIN = e Z (15 m)

4 ! "#$% &'(( ) +*,&-.0/ Basin size: 2000 km x 2000 km, depth: 4 km Re1 = 3333 Re2 = Rt1 = Rt2 = 000 Nb layers: 10 1 Barotropic Ψ 1 surface density deviationρ y 0.5 y x x Depth (m) ρ (kg m 3 ) Total vertical density at (0.5,0.5) 465

5 ! "#$% &'(( ) +*,&-.0/ Kinetic Energy SSA Reconstruction Data Vector vec, RC Vector ssarcvec, M=296 Original Reconstruction MEM Spectrum Data Vector ssarcvec,m= y 2.8 y ;:=<>:@?=ACBEDGFHACIKJL:@M BF+NPO$ACMQSR?=ACBUTWV A,MX 8KYZA,?@?\[^]#_` AaObFBU<c[;X F+?@Jd 79e fkrza,jb:g_hy [6<c[;N?@:@M:@NiX j;mzas<>:@nj k 7>lm_nojqprBF+?=AaO2:\[sM ]L:tOY O2Y F nh_j ul[vbo2y;_hwxo?=acm6o2:@nw[sjbn:@?@?=aao2:\[sm k 465

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7 References (papers that benefited from DOE support for in blue; DOEsupported team members in red) Dijkstra, H. A., and M. Ghil, 2004: Low-frequency variability of the large-scale ocean circulation: A dynamical systems approach, Rev. Geophys., sub judice. Feliks, Y., M. Ghil, and E. Simonnet, 2004a: Low-frequency variability in the midlatitude atmosphere induced by an oceanic thermal front, J. Atmos. Sci., 61(9), Feliks, Y., M. Ghil, and E. Simonnet, 2004b: Low-frequency variability in the mid-latitude baroclinic atmosphere induced by an oceanic thermal front, J. Atmos. Sci., to be submitted. Feliks, Y., M. Ghil, and E. Simonnet, 2004c: Interannual and interdecadal oscillations in a coupled ocean atmosphere model. in preparation. Ghil, M., Y. Feliks, and L. Sushama, 2002: Baroclinic and barotropic aspects of the wind-driven ocean circulation, Physica D, 167, Simonnet, E., 2004: Quantization of the low-frequency variability of the double-gyre circulation in the presence of bottom friction, J. Phys. Oceanogr., to be submitted. Simonnet, E., M. Ghil, K. Ide, R. Temam, and S. Wang, 2003a: Lowfrequency variability in shallow-water models of the wind-driven ocean circulation. Part I: Steady-state solutions. J. Phys. Oceanogr., 33,

8 Simonnet, E., M. Ghil, K. Ide, R. Temam, and S. Wang, 2003b: Lowfrequency variability in shallow-water models of the wind-driven ocean circulation. Part II: Time-dependent solutions. J. Phys. Oceanogr., 33, Simonnet, E., T. Tachim-Medjo, and R. Temam, 2003c: Barotropic baroclinic formulation of the primitive equations of the ocean. Appl. Analysis, 82, Simonnet, E., M. Ghil, and H.A. Dijkstra, 2004a: Homoclinic bifurcations in the quasi-geostrophic double-gyre circulation. J. Mar. Res., submitted. Simonnet, E., M. Ghil, and H.A. Dijkstra, 2004b: Quasi-homoclinic behavior of the barotropic quasi-geostrophic double-gyre circulation. Chaos, to be submitted. Simonnet, E., T. Tachim-Medjo, and R. Temam, 2004c: Barotropicbaroclinic formulation of the primitive equations of the ocean, Applicable Analysis, 82: Simonnet, E., T. Tachim-Medjo, and R. Temam, 2004d: Higher-order approximation equations for the primitive equations of the ocean, Proc. Erice Conf. PDEs (J.-L. Lions & G. Stampacchia Festschrift), in press. Simonnet, E., T. Tachim-Medjo, and R. Temam, 2004e: On the order of magnitude of the baroclinic flow in the primitive equations of the ocean. Annali Mat. Pura Applicata, to appear. Sushama, L. U., K. Ide and M. Ghil, 2004: Spatio-temporal variability in a mid-latitude ocean basin subject to periodic wind forcing, J. Mar. Res., to be submitted.