Tide Gauge Sea Level Records

1
Tide Gauge Sea Level Records

• Current use in assimilation efforts
• mostly in tide and coastal models
• 50-year GECCO estimates (low weight, minimal
  impact)
• ECCO-GODAE (on-going)
• checking assimilation results (SODA)
• Potential usefulness
• efforts extending to pre-altimeter era
• multi-decadal records
• dense time sampling relative to other data
• information on low frequency large-scale steric
  height, heat content
• concurrent with altimeter era
• dense (daily/hourly) time sampling relative to
  altimeter
• high frequency information (large-scale
  barotropic signals, equatorial waves)

2
Available data

• University of Hawaii Sea Level Center
  (hourly/daily)
• Permanent Service for Mean Sea Level (monthly)

mostly useful for delayed mode
3
Typical coverage
Total number of months with data (1992-2004)
4
Issues in using tide gauge data

• Inverted barometer correction (readily calculated
  from atmospheric surface pressure analyses not
  needed if ocean model includes pressure forcing)
• Tides (detiding procedures available need
  correction for both diurnal/semidiurnal and long
  period tides)
• Post-glacial rebound (particularly important for
  trends, corrections available from PGR models)
• Other relative signals (datum shiftsless of an
  issue for PSMSL monthly records earthquakes and
  tectonic motions sedimentation)

5
Errors

• No hard numbers available for instrument noise
  ( 1 cm for monthly estimates, likely higher for
  daily or hourly values -Pugh 2004)
• Largest errors related to representation issues
• localized effects of harbors, estuaries,
  continental shelves,
• errors in detiding, inverted barometer models
• geodetic noise

6
Effects of inverted barometer
Daily
Monthly
7
Checking optimization results
Change in correlation coefficient (optimized
minus control)
8
Data weights
cm2
9
Initial cost