Posts Tagged ‘sea level’

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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.

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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 9, the Baltic Sea

October 23, 2013

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 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.

The Baltic Sea

There are 22 tide gauge stations in the Baltic Sea area that are at least 90% data complete from 1960 to 2005.  Eighteen of those are 90% complete all the way back to 1930 and ten are 90% complete back to 1900.  The weighting (using a 200 km threshold) is nearly constant for the entire 20th century (see weighting graph below).  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.)

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Conclusion

The following graph makes clear that the Baltic Sea tide gauge data DOES reconcile the sea level rise rate from the tide gauge data with the higher late century rise rate from the satellite data.

Baltic Sea Detrended Acceleration annotated 2
On the other hand, the tide gauge sea level rise rate immediately before the era of satellite data is higher than rise rate after….

Baltic Sea Detrended Acceleration annotated 3

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

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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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