Modeling Tides for Southern Modeling Tides for Southern Ocean GLOBECOcean GLOBEC
Susan Howard and Laurence Padman
Earth & Space ResearchEarth & Space Research
MotivationMotivation
• Tidal currents are “noise” in ship ADCP
records. A model helps us remove them to
highlight the mean circulation.
• Tides contribute to benthic stirring and
pycnocline mixing.
• Ocean-applied stresses on the sea-ice base
affect ice kinematics and surface buoyancy
exchanges.
TopicsTopics
• 2-D model
Description of model
Results
Validation
• 3-D model (preliminary work):
Description of model
Results
2-D Model: CATS2-D Model: CATS
Resolution: The resolution is 1/4o E/W and 1/12o N/S (~10 km at 70oS).
Forced by height fields along 58oS obtained from the Oregon State University TPXO5.1 global tidal solution.
CATSCATS
Model
Domain
2-D Model: CATS2-D Model: CATS
Resolution: The resolution is 1/4o E/W and 1/12o N/S (~10 km at 70oS).
Forced by height fields along 58oS obtained from the Oregon State University TPXO5.1 global tidal solution.
Bathymetry: modified ETOPO-5.
Constituents: K1,O1,P1,Q1, M2,S2,N2,K2,Mm,Mf.
K1 M2
CATS ModelCATS Model
• Mean tidal speed
10 Constituents
• Weak tides except at shelf break
• Tides at shelf break diurnal (TVW)
• Currents will be affected by bathymetry
Tidal Signal in DriftersTidal Signal in Drifters
• Max speeds
15 cm s-1
• Diurnal band
only
• Speed varies
with position &
spring neap cycle
• Evidence of
strong tides near
shelf break
CATS vs. Moorings CATS vs. Moorings
3-D Model: POM3-D Model: POM
Resolution: The resolution is 1/8o E/W and 1/15o N/S (~8 km).
(we want to work toward a 2-4 km res.)
Forced by normal flow at open boundaries (taken from CATS).
POMPOM
Model Domain
(preliminary)
3-D Model: POM3-D Model: POM
Resolution: The resolution is 1/8o E/W and 1/15o N/S (~8 km).
Forced by normal flow at open boundaries (taken from CATS).
Bathymetry: modified ETOPO5.
Constituents: K1 and M2, modeled separately.
K1K1
Adelaide Island
M2
Adelaide Island
K1
Adelaide Island
M2
M2 M2
ConclusionsConclusions
• Tidal currents are quite weak except at the shelf break.
• Internal tides may be generated by both diurnal and semidiurnal flows across the upper continental slope.
• Surface tidal currents move the ice pack around, and may also increase open-water fraction.
• Lots of room for model improvements!
AcknowledgementsAcknowledgements
We would like to thank Dick Limeburner
for providing us with drifter data and Lana
Erofeeva for help with tide modeling.
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