SO503, Spring 2005

Tide Gauge Records

You should look at the paper by Douglas and Peltier (March 2002, Physics Today), which you can get  through the Nimitz Library.

The Permanent Service for Mean Sea Level  (once at http://www.pol.ac.uk/psmsl/) contains world wide tide gauge records:

http://ilikai.soest.hawaii.edu/uhslc/iotd/index.html?136,65 --tsunami records

Part I. 

Get one of the long term records from PSMSL (Amseterdam, Liverpool, or Stockholm), and run a regression to determine the rate of sea level change here.  What are the units?  (This is an Excel task; find the data, import it, and get the regression).

Part II.

Discuss the pattern of global sea level rise from tide gauge data, and how you can use a GIS to discover this.  This is intended to be a coherent, thought out response, into which you can incorporate figures, maps, or diagrams (including even the answer to Part I).  It is not supposed to be a shotgun answer to a number of questions, for instance those on this page lower down.  We have two databases with sea level rise data, in c:\mapdata\database\tides.  The Hawaii data links to actual tidal records (daily averages) for each station.

To help you in part II, the following questions are designed to force you to see how the GIS works (make sure you understand what filters and queries are).  You can answer as few or as many as you want; you do NOT have to turn in these answers. 

We have data for 419 tide stations, courtesy of the University of Hawaii ( http://uhslc.soest.hawaii.edu/ ) and 1141 stations from PSMSL.  The duration of the Hawaii records ranges from 1 to 99 years.  The values are average sea level height by day.  The average rate of sea level rise is indicated for the stations whose record exceeds 18 years.

The MICRODEM program will now plot the locations of the tide stations, and then let you plot the tide records.  Follow the following steps to plot a tide station:

·        Start MICRODEM program.

·        Open the tides data base.

·        A map will appear with the locations of the 419 stations.

·        You can force the map to redraw with the blue arrow button over the map.

·        You can color code by duration of the record by selecting the “Plot” button on the database, and then picking "color code by numeric field", and picking Duration.

·        You can also color code by the computed Rise.

·        You can Filter the data set using the “Filter” button.  This letter set a parameter and conditions, and only see those stations that match the filter conditions.

·        You can graph a station by Picking the TS button on the map toolbar, and then clicking on the station.

·        Return to all stations using the “All stations” button.

  

Look at the record for San Francisco.

·        Use the Analyze, Linear Fit menu choice to see the best fit line.

·        The reported slope is in meters per day (the window title converts it to mm/year).

·        How much did sea level rise at San Francisco in this time interval?

·        What happened to sea level from 1940 to 1950 (convert the rate from the Linear fit to mm/yr)?

·        How much do you trust this record to accurately reflect what is happening, and how long a record would you want to see?

  

Look at the stations for the Galapagos Islands (on the equator at W90).

·        What unusual patterns can you see?

·        Do you trust the trends?

  

Look at the stations for Galveston TX and Grand Isle LA.

·        What characterizes these stations, and how good are their records?

·        What is the longest period at these stations that would appear to record dropping sea level?

·        How long do you think the record has to be to accurately reflect the sea level change in this region?

  

How many stations have a record:

·        >95 years?

·        >50 years?

·        >18 years?

 How many southern hemisphere stations have a record:

·        >95 years?

·        >50 years?

·        >18 years?

 Of the stations with a record > 18 years, how many have seen

 What 3 stations have seen the largest sea level rise, and where are they located?  What factors there could account for this rise?

 What 3 stations have seen the largest sea level drop, and where are they located?  What factors there could account for this drop?

 What is the average rate of sea level rise for all the stations? (Look at the Stats button before you despair)

 What is the average rate of sea level rise for all the stations that are seeing a rise?

 What is the average rate of sea level rise for all the stations that are seeing a drop?