NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES Impacts of Sea Level Change and Vertical Land Movement on Tidal Datums Stephen Gill, Senior Scientist NOAA Center for Operational Oceanographic Products and Services TechSurge: Technical Support for Coastal Resiliency June 4, 2014 Norfolk, VA
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Impacts of Sea Level Change and Vertical Land Movement on Tidal Datums gill_MTS... · 2014-06-03 · TIDAL DATUMS In general, a datum is a base elevation used as a reference from
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NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Impacts of Sea Level Change and Vertical
Land Movement on Tidal Datums
Stephen Gill, Senior Scientist
NOAA Center for Operational Oceanographic Products and Services
TechSurge: Technical Support for Coastal Resiliency
June 4, 2014
Norfolk, VA
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Outline
Tidal datums and their applications
101
National Tidal Datum Epoch (NTDE)
NTDE updates and sea level change
Effects of rapid rates of vertical land
motion
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
TIDAL DATUMS
In general, a datum is a base elevation used as a reference from which to reckon heights or depths.
A tidal datum is a standard elevation defined by a certain phase of the tide from observed data.
Tidal datums are used as reference elevations for local water levels and should not be extended into areas having differing tidal and oceanographic characteristics without substantiating measurements.
In order that they may be recovered when needed, such datums are referenced by leveling surveys from the sensors to fixed points known as bench marks.
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Tidal Datum Application to Nautical Services
The vertical water level datum to which charted
soundings on a nautical chart are referred. This is
called Chart Datum.
For USA nautical Chart Datum is Mean Lower Low
Water (MLLW) for tidal areas or a Low Water Datum
(LWD) for non-tidal areas.
NOAA tide table and tide prediction products and
elevations are referenced to MLLW
Mean High Water (MHW) defines the official shoreline
for the USA.
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Maritime Boundary Applications of Tidal Datums
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
• A specific 19 year period (currently 1983-2001) that includes the longest
significant periodic tidal variation caused by the astronomic tide-
producing forces.
• Averages out meteorological, hydrologic, and oceanographic fluctuations.
• Provides a nationally consistent tidal datum network by accounting for
seasonal variations and apparent trends in sea level that affect the accuracy
of tidal datums.
• The National Water Level Observation Network (NWLON) provides the
data required to maintain the NTDE and make primary and secondary
determinations of tidal datums.
NATIONAL TIDAL DATUM EPOCH (NTDE)A common time period to which tidal datums are referenced
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
The National Water Level Observation Network
210 NWLON Stations
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
TIDE STATION HEIRARCHY FOR
DATUM DETERMINATION
SECONDARY TIDE STATION:
• minimum of 1 yr but less than 19 yrs
PRIMARY TIDE STATION:
• minimum of 19 years
• allows statistical and datum control for short term stations
TERTIARY TIDE STATION:
• more than 30 days but less than a year
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Errors in Tidal Datums and Duration of Observation
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Sewells Point, Hampton Roads Tide Station
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Tabulation of the Tide and Monthly Means
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
A First Reduction Determination of Tidal Datums – 19-year NTDE
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Published Sheet for Tidal Bench Mark Elevations – Sewells Point, Hampton Roads
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES