E-FLUX: An Investigation of Eddy Dynamics in the Lee of Hawaii. OCN 621: Biological Oceanography Bob Bidigare

Transcription

1 E-FLUX: An Investigation of Eddy Dynamics in the Lee of Hawaii OCN 621: Biological Oceanography Bob Bidigare 17 February 2006

2 Isolated Vortices Isolated vortices (IVs) are formed via numerous processes including: - Direct generation by wind - Shedding from topography - Instability of wind- and thermallydriven circulations (western boundary currents and other jets) - Localized convection (2 nd baroclinic mode eddies) Examples of IVs include rings and eddies

3 Examples of Isolated Vortices Wind Generation Current-Topography Interactions Circulation Instabilities

4 Isolated Vortices Influence plankton and planktonic processes via: - Horizontal transport of biota Δ distribution (swirl velocity > translational speed) - Dispersal of IV biota to adjacent parcels (diffusion) Δ distribution - Vertical motions (upwelling and downwelling) that affect the availability of light and nutrients Δ rates of biological processes

5 Vertical Displacements of Isopycnal Surfaces Within IVs Non-linear Light Effects Exponential in PAR Exponential in PAR McGillicuddy et al. (2004)

6 Eddies 1 st baroclinic cyclones 1 st baroclinic anticyclones 2 nd baroclinic mode water eddies McGillicuddy et al. (1999)

7 Eddies PP PP PP PP PP PP Flierl & McGillicuddy (2004)

8 Eddies Enhanced biological activities have been reported for each eddy type as evidenced by measurements of carbon fixation, nutrient uptake and oxygen production (Falkowski et al. 1991, Allen et al. 1996, McNeil et al. 1999, Zhang et al. 2001) Primary production rates within these features are are thought to be stimulated by the input of growth-limiting nutrients that results from (i) the upward displacement of nutrient-rich isopycnal surfaces and (ii) larger vertical eddy diffusion coefficients

9 Hawaiian Eddies: Historical Perspective Patzert (1969) - Atmospheric forcing and eddy genesis - Eddy hydrography (CTD surveys) - Theoretical analysis and modeling Lobel and Robinson (1985, 1986) - Eddy influences on coastal currents (transport) - Role of eddies in the recruitment of larval fish

10 Hawaiian Eddies: The 1989 Eddy Study Falkowski et al. (1991) - Effects of eddy pumping on primary production rates (FRR fluorometry) Olaizola et al. (1993) - Effects of eddy pumping phytoplankton distributions and community structure Allen et al. (1996) - Effects of eddy pumping on primary productivity ( 14 C) and new production rates ( 15 N)

11 Hawaiian Eddies: Historical Perspective Lumpkin (1998) Ph.D. Dissertation Eddies and Currents of the Hawaiian Islands - Utilized Drifter, ADCP, sea level record, TOPEX altimetry and AVHRR SST data - Developed models to describe the genesis, cyclogeostrophic balance, and propagation of Hawaiian cyclonic and anti-cyclonic eddies

12 Hawaiian Lee Eddies (R o = Rossby number = ζ/ƒ, core vorticity / Coriolis parameter) Lumpkin (1998)

13 Seki et al. (2001): Cyclone Loretta September 1999 November 1999

14 Cyclone Loretta (November 1999) Seki et al. (2001)

15 Hawaiian Eddies: Historical Perspective Holland and Mitchum (2001) - Investigated the propagation of Hawaiian anticyclonic eddies using TOPEX/Posiedon imagery Seki et al. (2002) - Investigated the influence of cyclonic eddies on the distribution of the Pacific blue marlin (catch data) Chavanne et al. (2002) - Investigated the effects of the Hawaiian Islands on mean atmospheric flow (NSCAT and aircraft data)

16 Hawaiian Lee Eddies: Chavanne et al. (2002)

17 Hawaiian Lee Eddies

18 Bidigare et al. (2003): Cyclone Haulani November 2000 January 2001

19 Cyclone Haulani NEC IN OUT NEC IN OUT NEC IN OUT Pigments (0-150 m) Increase Decrease Vaillancourt et al. (2003)

20 Cyclone Haulani Vaillancourt et al. (2003)

21 PARAMETER OUTSIDE OUTSIDE HAULANI INSIDE HAULANI HAULANI IN/OUT Carbon Export Parameters 234 Th flux (dpm m -2 d -1 ) 643 ± ± > 53 μm C (μmol kg -1, 150 m) ± ± C/ 234 Th (μmol C dpm -1 ) 1.59 ± ± C Flux (mmol C m -2 d -1 ) 1.02 ± ± Primary Prod (mmol C m -2 d -1 ) 56 ± ± C Flux/C PP 1.8% Bidigare et al. (2003)

22 Euphotic Zone Isopycnals Displacement Effects of Time on Eddy Processes in the Sargasso Sea (BATS Site) Intensifying Mature Decaying depth distance depth distance depth distance Background Nutrient injection time Background Biological response Export (1) (2) (3) (4) (5) (6) (7) Stages in an Eddy s Life Cycle Sweeney (2001)

23 E-FLUX ( eddy flux ) Experiment Funded by the National Science Foundation Investigators - Claudia Benitez-Nelson (USC) - Bob Bidigare and Sue Brown (UH) - Tommy Dickey (UCSB) - Mike Landry (SIO) - Carrie Leonard (BAE Systems Spectral Solutions) - Paul Quay (UW) Collaborators: D. Karl, C. Mahaffey, M. Saito, P. Falkowski, M. Rappé, W. Cai & K. Richards, Y. Chao & F. Chai

24 E-FLUX Experiment E-Flux Goal: Provide in situ estimates of the upper and lower limits of mesoscale eddy effects on local biogeochemical cycling such that they can be used to test, evaluate, and reformulate the various models for assessing eddy influences on larger regional and basin spatial scales E-Flux hypothesis: The interaction of the NE trade winds with the Hawaiian Island topography acts as a trigger to set in motion a cascade of events that results in an increased carrying capacity of this subtropical ecosystem and enhanced rates of particulate matter export E-FLUX website:

25 E-Flux Hypothesis

26 E-FLUX Research Objectives Determine how (mechanistically) and where production, planktonic community biomass and export flux are enhanced in an eddy flow field Quantify the net effects of first baroclinic mode cyclonic eddies on trophic processes and carbon export relative to the ambient oligotrophic system

27 State-of-the-art techniques utilized during E-Flux to identify and quantify physical-chemical-biological interactions on a variety of time and space scales

28 State-of-the-art techniques utilized during E-Flux to identify and quantify physical-chemical-biological interactions on a variety of time and space scales

29 Euphotic Zone Isopycnals Displacement E-FLUX Experiment E-Flux was designed to study three main phases of the eddy life cycle: - Spin-up (E-Flux II): January Mature (E-Flux III): March Relaxation (E-Flux I): 4-22 November 2004 Intensifying Mature Decaying depth distance depth distance depth distance Background Background time Nutrient injection Biological response Export (1) (2) (3) (4) (5) (6) (7)

30 E-Flux III: Preliminary Findings (March , R/V Wecoma) Depiction of the E-Flux III study region: 50-m current vectors and 45-m density contours clearly show the presence of Cyclone Opal whose diameter was over 200 km (T. Dickey)

31 E-FLUX III: Cyclone Opal Dickey et al. (2005)

32 E-FLUX III: Thermal imagery

33 Bidigare et al. (2005)

34 E-FLUX III: Drifter data Bidigare et al. (2005)

35 E-FLUX III: Cyclone Opal Dickey et al. (2005)

36 E-FLUX: Cyclone Opal Dickey et al. (2005)

37 E-FLUX: Transect 3 Density (σ t ) Chl a (mg L -1 ) Velocity (m s -1 ) Dickey et al. (2005)

38 Bidigare et al. (2005)

39 E-FLUX III: Transect 3 F m : ~ [Chl a] F v /F m : ~ Φ max Bibby & Falkowski (2005)

40 Cyclone Opal: Phytoplankton OUT (> 8 μm fraction, 500 ml) IN (> 8 μm fraction, 500 ml) S. L. Brown (2005)

41 Cyclone Opal: IN Station Time-series Bidigare et al. (2005)

42 Future Directions Couple these in situ measurements with highresolution 3-D circulation/food web models Regional Ocean Modeling System (ROMS) ROMS, in its 3-level (15-, 5-, 1.5-km) nested version, has been successfully tested in the Monterey Bay during a real-time (August 2003) field experiment; Both in situ and satellite observations have been assimilated into ROMS to produce a month-long reanalysis fields Yi Chao (JPL)