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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
Why 19-years for a Tidal Datum Determination?
The 18.61 – year Lunar Nodal Cycle
http://tidesandcurrents.noaa.gov/publications/Understanding_Tides_by_Steacy_finalFINAL11_30.pdf
Axis of earth’s rotation is inclined 23.452 degrees to the plane of ecliptic;
Plane of the orbit of the moon is inclined 5.145 degrees to the plane of the ecliptic;
Maximum monthly declination of the Moon varies between 28.597 and 18.307 degrees every 18.61 - years
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
The 18.61-year Lunar Cycle – the Node Factor for Tidal Constituent Amplitudes used in Tidal Analysis and
Prediction
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Long-term Variations in Monthly and Annual Mean Range of Tide
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Effects of 18.61-year Lunar Nodal Cycle at Hampton Roads
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
NATIONAL TIDAL DATUM EPOCH UPDATES
1983-01 EPOCH
NTDE UPDATES ARE REQUIRED IN ORDER TO ACCOUNT FOR
RELATIVE SEA-LEVEL CHANGE OVER TIME
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Relative Sea Level Trends at National Water Level
Observation Network (NWLON) Stations
http://tidesandcurrents.noaa.gov/sltrends/sltrends.html
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
The Relative Mean Sea level Trend at Sewells Point, Hampton Roads
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Impacts of Sea Level Rise on Tidal Heights
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
History of Tidal Datum Updates at Sewells Point, Hampton Roads
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
NTDE Updates at Sewells Point, Hampton Roads
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Effects of Vertical Land Motion and
Relative Sea Level Trends
http://tidesandcurrents.noaa.gov/sltrends/sltrends.html
* Tide stations measure sea level variation
relative to the local land.
* Sea level variations at any station can be due
to global sea level rise from climate change;
from shelf and estuarine changes in
hydrodynamics and circulation patterns due
to decadal climate oscillations; and changes
in freshwater flow into estuaries
* Long-term sea level variations can also be
due to local and regional vertical land
movement: either subsidence or uplift
• Tide gauge records do not distinguish as to
cause, but simply provide sea level variation
relative to the local land – a very important
piece of coastal intelligence for decision-making.
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Vertical Land Subsidence in Lower
Chesapeake Bay Region
Source: USGS Circular 1392
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Vertical land Motion – Subsidence in Louisiana
Source; NASA, JPL, LSU
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Tidal Datum Updates at Grand Isle LA
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Vertical Land Motion – Isostatic Rebound – Southeast Alaska
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Tidal Datum Updates at Juneau AK
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Tidal Datums and Vertical Land Motion – Recent Reports
http://tidesandcurrents.noaa.gov/publications/
NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Tidal Datums and Future Sea Level Projections
83-0102-20
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NOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICESNOAA’s CENTER for OPERATIONAL OCEANOGRAPHIC PRODUCTS and SERVICES
Questions?