clivar/godae synthesis evaluation item#5: volume transport, temperature & salinity fluxes...
TRANSCRIPT
CLIVAR/GODAE Synthesis Evaluation
Item#5: volume transport, temperature & salinity fluxes through key straits:
• Indonesian throughflow (ITF)
• ACC at Drake Passage
• Florida Current at Florida Strait
Tony Lee, JPL
Some details about legends
3D-VAR
RTS smoother
ITF
ITF volume transport (Sv)
Anomaly relative to 1993-2001 mean
Total
Spinup problem
Remarkable consistency
Island Rule doesn’t work? Or effect of geometry/topography?
ITF volume transport from 1992 (Sv)
Total
Anomaly relative to 1993-2001 mean
ITF temperature flux (PW)
Total
Anomaly relative to 1993-2001 mean
ITF temperature flux from 1992
Total
Anomaly relative to 1993-2001 mean
ITF salinity flux
Total
Anomaly relative to 1993-2002 mean
ITF salinity flux from 1992
Total
Anomaly relative to 1993-2001 mean
1993-2001 averaged seasonal anomaly of ITF
ITF property flux (volume, heat, and salt) estimated by various products are overall consistent (for mean as well as for seasonal, interannual, and decadal variability: e.g., large magnitude of seasonal cycle relative to mean value, low ITF during El Nino, lack of decadal variability.
ACC
ACC volume transport
Total
Anomaly relative to 1993-2001 mean
ACC volume transport from 1992
Total
Anomaly relative to 1993-2001 mean
ACC temperature flux
Total
Anomaly relative to 1993-2001 mean
Relatively consistent decadal variability
No such large adjustment in volume transport
ACC temperature flux from 1992
Total
Anomaly relative to 1993-2001 mean
ACC salinity flux
Total
Anomaly relative to 1993-2001 mean
ACC salinity flux from 1992
Total
Anomaly relative to 1993-2001 mean
1993-2001 averaged seasonal anomaly of ACC
Relatively large difference in mean and seasonal variability, but relatively consistent on decadal time scale.
Florida Current at Florida Strait
Two different ways of computing Florida Current (FC) transport by various groups:
(1) meridional transport near 26.5N between Florida (~80W) to 75W (more consistent with cable measurements),
(2) zonal transport between Florida and Cuba (better defined in models).
The time mean of (2) is significantly smaller than that of (1) because a portion of (1) comes through a “short circuit” north of the Caribbean instead of from the loop Current (esp. in models)
FC volume transport
Anomaly relative to 1993-2001 mean
Total
Grey curve – cable data
FC volume transport from 1992
Total
Anomaly relative to 1993-2001 mean
Grey curve – cable data
Zonal (upper) and meridional (lower) Florida Current transports
Zonal: between Florida & Cuba (well-defined)
Meridional: 26.5N, 80-75W (near cables)
Grey curve – cable data
FC temperature flux
Total
Anomaly relative to 1993-2001 mean
FC temperature flux from 1992
Total
Anomaly relative to 1993-2001 mean
FC salinity flux
Total
Anomaly relative to 1993-2001 mean
FC salinity flux from 1992
Total
Anomaly relative to 1993-2001 mean
1993-2001 averaged seasonal anomaly of Florida Current
Relatively large spread, partly because of definition problem.
In most models, the flow going into the Gulf of Mexico is weak; some flow take a short cut north of Cuba to joint the Florida Current.
Summary Statistics
ITF FC ACC ITFt ITFs FCt FCs ACCt ACCs
Sv Sv Sv PW PW PW Kg/s Kg/s Kg/s
K7 -12.4 157
CRFS-A -12.9 16.6 147
CRFS-2 -13.2 24.2 147
ECCO-50yr -11.0 29.3 129 -1.0 -0.4 2.1 1.1 1.4 4.5
ECCO-SIO -10.7 30.6 154 -0.9 -0.4 2.2 1.1 1.6 5.3
ECMWF -10.6 14.8 148
GFDL -15.7 24.3 171 -1.0 -0.6 1.6 0.8 1.7 6.1
INGV -11.9 24.6 127 2.8 0.9
MOVE-G -23.4 179
ECCO-JPLKF -13.2 27.6 132 -1.2 -0.5 2.3 1.0 1.4 4.6
MCTR 3DVAR -18.7 15.0 142
MCTR KF -12.8 21.8 149
ECCO-GODAE -11.1 26.6 148 -0.9 -0.4 1.9 1.0 1.5 5.1
SODA -14.5 27.5 158 -1.2 -0.5 2.1 1.0 1.7 5.6
Obs. Analysis -10 ~ -15
31.9 120~160
1993-2001 mean transports/fluxes: For Florida Current: black - meridional transport near 26.5N, 80-75W; red – zonal transport between Florida & Cuba.
The largest mean ITF (> 23Sv): consistent with Island rule (integration of South Pacific curl)? Or effect of geometry/topography?
High mean ACC transports (170-180 Sv): too strong zonal wind? lack of form drag due to smooth topography? Small viscosity?
(all in Sv) ITF FC ACC rms dev. of FC from cable data
K7 3.5 7.0
CRFS-A 5.0 4.7 6.4 4.9
CRFS-2 5.2 4.7 6.2 5.3
ECCO-50yr 2.4 1.6 4.1 2.9
ECCO-SIO.it69 2.5 2.2 4.6 3.1
ECMWF 3.0 2.2 4.0 3.0
GFDL 2.5 2.8 5.0 3.6
INGV 3.1 5.6 3.5 5.5
MOVE-G 4.0 6.3
ECCO-JPL RTS smoother 3.0 3.0 4.1 3.4
MCTR 3DVAR 5.5 5.1 6.6 5.3
MCTR KF 3.2 1.4 4.6 2.8
ECCO-GODAE.v2.199 2.6 2.2 4.4 3.3
SODA 4.3 2.6 4.5 5.0
rms diff. among models 2.3 3.0 3.5
Measurement 2.5
1993-2001 rms variability of volume transport, rms difference among models, and rms difference from cable measurements