Posts Tagged ‘Sea Level Rise’

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The Search for Acceleration, part 10, US Gulf Coast

February 17, 2014

magnifying glass 145This is part 9 of a series of posts in which I am searching for a large acceleration in sea level rise rate in the latter part of the 20th century.  Such a rise rate is needed  to reconcile the 1.8 mm per year average rise rate for the century attributed to tide gauge data and the approximately 3 mm per year rise rate for the tail end of the century attributed to the satellite data.

U.S. Gulf Coast

This region  has 4 tide gauge sites with at least 90% data completion between 1950 and 2008.  Three of the sites have data back to 1930 or earlier .  I will analyse this data in my usual manner: detrending, weighting, averaging and derivatives.

This slideshow shows my standard analysis.

This slideshow requires JavaScript.

Conclusion

One thing is certain from the above graphs: the sea level rise rate in the US Gulf Coast region has not shown an acceleration in the last part of the 20th century or the 21st century. The rise rate reached a peak in the 1940s and has been dropping since around 1970.

Keep in mind that there are many factors that contribute to the rise rate in this region.  Subsidence is the primary cause, and subsidence itself has multiple components.

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The Search for Acceleration, part 8, Hawaii

August 16, 2013

magnifying glass 145This is part 8 of a series of posts in which I am searching for a large acceleration in sea level rise rate in the latter part of the 20th century.  Such a rise rate acceleration is needed  to reconcile the 1.8 mm per year average rise rate for the century attributed to tide gauge data and the approximately 3 mm per year rise rate for the tail end of the century attributed to the satellite data.

Hawaii

There are only four tide gauge stations in Hawaii with at least 90% of the data from 1960 to 2008.  One of them has good data back to 1910.  Evaluation of this small set of data sites is very simple and I will use the usual technique of detrending, weighting, averaging and derivatives, as shown in the following slide show.  (Note that you can pause or increment the slide show forward or backward by using the buttons that appear when your cursor is placed over the image.)

This slideshow requires JavaScript.

It is very hard to make an argument in support of a century end acceleration in sea level rise rate based on this Hawaiian data.

ENSO

SInce I removed the ENSO correlated component of the sea level for Western North America and for Australia, it stands to reason that the same thing should be done for Hawaii.  See here for the math.

The top graph in the following image shows the weighted, detrended, averaged Hawaiian  sea level (white), ENSO3.4 sea surface temperature (blue),  and the component of sea level data that is orthogonal to the ENSO3.4 data (red).  The bottom graph shows the corresponding relative rise rates associated with sea level (white) and with the ENSO orthogonal component of the sea level (red).  All data is through a 5 year FWHM Gaussian filter.

Rise rate orthongonal to ENSO
The correlation is small and, if anything, subtraction of the ENSO correlated component of the sea level makes a century end acceleration look even less plausible.

See an index of the Search for Acceleration series here.

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Sources

20th century rise rate average of 1.8 mm/year

1. Church and White Global Mean Sea Level Reconstruction

2. Links to Church and White sea level data

Satellite data (about 3 mm/year): CU Sea Level Research Group

RLR tide gauge data: Permanent Service For Mean Sea Level

ENSO/Global warming relationship: Cobb, et. al., Science, 339, 1/4/13

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The Search for Acceleration, part 7, Western North America

July 30, 2013

magnifying glass 145This is part 7 of a series of posts in which I am searching for a large acceleration in sea level rise rate in the latter part of the 20th century.  Such a rise rate is needed  to reconcile the 1.8 mm per year average rise rate for the century attributed to tide gauge data and the approximately 3 mm per year rise rate for the tail end of the century attributed to the satellite data.

Western North America

This region  has 13 tide gauge sites with at least 90% data completion between 1950 and 2008.  Seven of the sites have data back to 1920 or earlier (but with some gaps).  I will analyse this data in the same manner as the Australian data.  I will start with the usual detrending, weighting, averaging and derivatives.  Then, I will find the portion of the sea level that is orthogonal to the ENSO3.4 sea surface temperature.

This slideshow shows my standard analysis.

This slideshow requires JavaScript.

 

ENSO

Like Australia, the sea level around the Western coast of North America seems to be related to the El Nino Southern Oscillation.  The following plot shows an overlay of the detrended weighted average of the 13 Western North American tide gauge sites and the NINO3.4 index from the Hadley Centre.  Both are detrended from 1920 to 2008.  Note that the ENSO data scale is inverted.

Enso and Western North America

Now I will  remove the part of the sea level data that correlates to ENSO  by breaking the sea level data down into ENSO correlated and ENSO orthogonal parts. If the ENSO orthogonal part of the sea level is truly independent of ENSO, then it shows what the sea level around Australia would look like without an ENSO effect. Here is the formula for finding the ENSO orthogonal component of the of the sea level data.

 

Conclusion

The highest rise rate during the period covered by this data occurs around 1980.  But that peak was gone before the the beginning of satellite data.  The 1990s and 2000s show some high and low rise rates, but the highs are no higher than the 1930s, and the lows are lower than the 1940s.  Despite some periods of high rise rates in the 1990s and 2000s, the average rise rate does not indicate a large acceleration over the earlier part of the century.  These conclusions are the same whether or not the ENSO correlated part of the sea level is removed.

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Sources

20th century rise rate average of 1.8 mm/year

1. Church and White Global Mean Sea Level Reconstruction

2. Links to Church and White sea level data

Satellite data (about 3 mm/year): CU Sea Level Research Group

RLR tide gauge data: Permanent Service For Mean Sea Level

ENSO/Global warming relationship: Cobb, et. al., Science, 339, 1/4/13

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