1. Preliminary Results from the Global Ocean Simulations with the Baringer-Price-Yang Marginal Sea Boundary Condition Model
Wanli Wu, William Large and Gokhan Danabasoglu
National Center for Atmospheric Research
OUTLINE
Baringer-Price-Yang Marginal Sea Boundary Condition (MSBC) model
Implementation of the MSBC model into POP
Preliminary Results
Ongoing and Future work

2. The Strait of Gibraltar
Geometry parameters:
Location: (36N,6W)
Width (W): 20km
Sill depth (D): 280m
Shelf-slope break (ssb) depth: 400m
Slope of ssb: 0.012

3. The MSBC model (Baringer & Price, 1997, Price & Yang, 1997)
Exchange dynamics (Bryden & Stommel, 1984; Bryden & Kinder, 1991)
Outflow/inflow fluxes: Ms=-Mi = 0.07 g ’1/2 D 3/2 W, g’=g(rs-ri)/rs
Entrainment & Product: (Baringer & Price, 1994; Price and Yang, 1997)
Entrainment rate ~~ Froude number F=g’a/f (g’h)1/2
Product water flux is given by Mp=MsF2/3
Entrained water flux is then given by Me=-(Mp+Mi)
Their steady MSBC process model requires
Climatological T & S profiles from the open ocean water properties, and
Climatological fresh water flux (E-P) and heat flux (Q) of the marginal sea
to derive density difference (rs-ri)
then --> mass transport (volume fluxes)
Density difference was given by E-P, and heat fluxes over the Mediterranean Based on assumption: Mass, heat and salt conservation
Observed product water ~ 900~1200m
Entrained level determined by the strait geometry (~400m)

4. Implementation of the MSBC model into POP
Implementation of the process model into POP (~3o) to simulate water transport crossing the Gibraltar Strait
The strait is currently closed in the model
Use instantaneous Ti, Ts, Si and Ss from model instead of climatological Ti, Si, E-P and Q,
Time-varying MSBC,
Based on T & S profiles to compute density difference , then volume fluxes: Ms (Mi), Me and Mp
From volume fluxes --> velocity (Ui, Us, Ue, Up), then replace the zero velocity and (T&S) fluxes (UT, US) on the open ocean and marginal sea interface.
Experiments: 50-year POP runs with/without MSBC

7. Outflow water properties
model
observed
sources
mean inflow transport (sv)
0.9
0.9~1.8
Bryden et al, 1989
seasonality: Max
Min
Amp
March
August 6%
Spring
Fall
Bormans et al., 1986
current velocity(m/s)
0.64
0.6
Baringer et al., 1997
salinity difference(psu)
1.80
2.12
Product water
depth(m)
salinity (psu)
potential temperature (C)
815~985
37.15
13.82
915
36.46
12.74
Price & Yang, 1997

12. Summary
A time-dependent Marginal Sea Boundary Condition (MSBC) model was implemented to an OGCM, and applied for the Gibraltar Strait overflow.
The model with MSBC simulated reasonable water properties and seasonal cycle of the water exchange through the Strait.
The model with MSBC also realistically reproduced the warm and saline tongue in the North Atlantic.

13. Ongoing Research and Future Work (open for discussion!)
Testing the same scheme in POP with higher resolution (~1o with open strait)
Implement the MSBC into other places like Faroe Bank Channel, Denmark Strait.
Long-term ocean alone simulation
Coupled simulation for climate impact study