Nested Models: A Synthesis Tool Tom (Zack) Powell, UC Berkeley U. S. GLOBEC Pan-Regional Synthesis Meeting Nov, Boulder, CO

“...concentrating on a few systems is preferable.” “HAS GLOBEC EVOLVED A SUCCESSFUL STRATEGY TO ATTAIN ITS GOALS?”... “...The effect of greenhouse gas-induced global change is expected to be felt in all oceans, and GLOBEC, to be truly global, could have devised a program that would simultaneously study all, or at least, many ocean ecosystems simultaneously.” - J. Knauss et al., Dec, “...Understanding how a given ecosystem will respond to global change generated by greenhouse gas warming is much more difficult and unlikely to be achieved within the lifetime of this program.” - J. Knauss et al., Dec, “SUMMARY”...

“...concentrating on a few systems is preferable.” “HAS GLOBEC EVOLVED A SUCCESSFUL STRATEGY TO ATTAIN ITS GOALS?”... “...The effect of greenhouse gas-induced global change is expected to be felt in all oceans, and GLOBEC, to be truly global, could have devised a program that would simultaneously study all, or at least, many ocean ecosystems simultaneously.” - J. Knauss et al., Dec, “...Understanding how a given ecosystem will respond to global change generated by greenhouse gas warming is much more difficult and unlikely to be achieved within the lifetime of this program.” “SUMMARY”...

1. Nested Models 2. Present Assessment 3. Future Prospects 4. Proposal OUTLINE

Nested Models

Nested Model Hierarchy in the North Pacific NPac (40 km) NEP (10 km) CCS&CGOA (3 km) PWS (1 km) 40 km10 km3 km1 km

Free surface, hydrostatic, primitive equation model Generalized, terrain-following vertical coordinates Boundary fitted, orthogonal curvilinear horizontal coordinates on an Arakawa C-grid Non-homogeneous time-stepping algorithm High-order advection schemes Accurate baroclinic pressure gradient (FV/splines) Continuous monotonic reconstruction of vertical gradients ROMS : KERNAL ATTRIBUTES

Model Setup. I. -Ocean Model: ROMS (community model) -Domain: Pacific basin; 30S to 65N, 100E to 70W. 476x238 Horizontal points, 30 vertical layers -Spinup: 10 years with climatological fluxes and daily winds -Hindcast: , NCEP winds and fluxes. Also Qscat winds

Model Setup. II. -Air-sea interaction boundary layer from COARE (Fairall et. al. 1996) -Oceanic surface boundary layer (KPP; Large et. al. 1994) -Bathymetry: ETOPO5, isobaths do not intersect coastline

Data (Bond et al.) Model (NPAC) SST anomaly

California Current

Aug SST SeaWiFS Chl Jul

Denman and Abbott 1994 (pigment, CZCS)

[P,T] decorrelation times (Denman and Abbott 1994) km km

Domain: N, W 514 x 510 x 30 gridpoints NCEP daily forcing (wind, heat flux) Initial, boundary conditions from NEP model Start: 1 Jan 2000 M-Y mixing Forward run (no data assimilation) CCS Implementation(ROMS)

. _. _. Stats ___ Calcs

Spitz et al (JGR 108)

Surface Section

Satellite Model

Present Assessment

Domain: N, 115 – 210E ROMS: 226 x 642 x 42 gridpoints Subdaily (6 hr) T42 CORE wind and fluxes (Large and Yeager) Initial/boundary conditions provided by CCSM-POP hindcast model Forward run for —includes multiple El Nino’s, Regime Shifts, and 2002 cold intrusion Daily averaged physical snapshots of velocity, temperature, etc. Especially want to thank Enrique Curchitser (Rutgers) and Kate Hedstrom (UAF) for providing these model fields. NEP Implementation

ATM OCE LNDCPLICE CCSM 3.0

Domain: N, 115 – 210E ROMS: 226 x 642 x 42 gridpoints Subdaily (6 hr) T42 CORE wind and fluxes (Large and Yeager) Initial/boundary conditions provided by CCSM-POP hindcast model Forward run for —includes multiple El Nino’s, Regime Shifts, and 2002 cold intrusion Daily averaged physical snapshots of velocity, temperature, etc. Especially want to thank Enrique Curchitser (Rutgers) and Kate Hedstrom (UAF) for providing these model fields. NEP Implementation

How well do the ROMS NEP physics match our perception and data from the real NEP ocean? 1)Compare SSH from the model with altimetry 2)Large scale climatology 3)Seasonality 4)Compare SST 5)Compare Subsurface Temperatures 6)Interannual Variability in Strength of the Alaskan Gyre Circulation and Bifurcation of the North Pacific Current (particle tracking)

Climatological Seasonal SSH Anomaly from Strub and James (2002) MODEL Both are contoured at 2cm intervals Positive SSH Anomalies Along Coast AC – Intensified CC - Weakened January SSH Anomaly

Climatological Seasonal SSH Anomaly from Strub and James (2002) MODEL Both are contoured at 2cm intervals Negative SSH Anomalies Along Coast AC – Weakened CC - Intensified July SSH Anomaly

Subsurface Temperature: Line P Seasonal Climatology Model has warmer subthermocline temperatures, and weaker cross- shore isotherm slope suggesting model is underestimating Alaska Gyre current velocity. From Line P web site

May 1987 Trajectories 1989 Trajectories 15 April – 14 June

May 1987 Trajectories 1989 Trajectories May 87 May 89

Summary 1)The current NEP model hindcast for is a significant improvement over earlier simulations. 2)Climatological SSH and SST match observations well at largest scales. 3)Model shows reasonable seasonal variation in coastal velocities (intensified AK gyre in winter; intensified CC in summer). 4)Modeled subsurface seasonal temperatures (at m) along Line P are ca. 2°C warmer than observations. 5)Alaska Gyre geostrophic transport through Line P is weak relative to observations. 6)10 m particle trajectories respond to instantaneous velocities including substantial mesoscale velocity (eddies). 7)However, is the NEP model product sufficient to use as the basis for coupled biophysical modeling of salmon, euphausiids, and LTL dynamics? 8)Temperature is important for bioenergetic models, but juvenile salmon are mostly in the upper meters (where the modeled T may be OK). 9)Mixed layer depth and stratification intensity are important for controlling nutrient flux into the euphotic zone. Increased nutrient fluxes due to weak stratification may lead to early and possibly sustained phytoplankton blooms, etc.

Future Prospects

“HAS GLOBEC EVOLVED A SUCCESSFUL STRATEGY TO ATTAIN ITS GOALS?”... “...lack of a specific program tied to investigate nutrients and food production for the targeted organisms;...” - J. Knauss et al., Dec, 1997.

NEMURO.FISH

Observations- Biological and Physical NCEP 6 hourly data (includes interannual variability) COCO – Tokyo 3-D Nemuro Zooplankton and temperature temperature time series Nemuro Pacific herring model Validation Time series output

PROPOSAL

* ROMS IMPLEMENTATIONS * * US GLOBEC OTHER * * * * * * * * * *

1. Simultaneously drive all U. S. GLOBEC regional ROMS + ecosystem models with a single, global climate model. 2. Simultaneously drive ALL GLOBEC International regional ROMS models with a single, global climate model. 3. Simultaneously drive all GLOBEC regional ROMS + E-2-E ecosystem models with a single, global climate model. Ultimately

END