SO422 Nearshore Oceanography

Tide Gauges and Global Sea Level Rise

Spring 2009

 

We have data for 419 tide stations, courtesy of the University of Hawaii (http://uhslc.soest.hawaii.edu/ ).  The duration of the 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 data file you want is a database C:\mapdata\tides\Univ_hawaii\tide_stations.dbf.

 

This will be be done in groups, and due in the Drop Box by 1330 hours on Tuesday 3 March.

 

Write a discussion on using tide gauges to determine sea level rise.  Insure that you address the following points, with examples and figures from the stations we have

The questions below are designed to get you started, and look at some of the records.  You are not required to answer the questions, but might want to incorporate some of the data in your discussion.

 

 

 

The MICRODEM program will  plot the locations of the tide stations, and then let you plot the tide records.  There are full directions in the program help file.  Follow the following steps to plot a tide station:

·        Start MICRODEM program and open a base map.

·        Open the tides data base with the DB button.  It will be in c:\mapdata\database\tides\univ_hawaii

·        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 lets you 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 on 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?

 

 

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

 

 

Installing the program and data:

For help and directions on the options that will be helpful, look in the help file for MICRODEM.  In the table of contents, go to Tutorials and Labs, Coastal Geology, Tide Gauges and Sea Level Rise.