Posts Tagged ‘Sea Level Rise’

h1

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.

h1

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.

_________________________________________

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

h1

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.

_________________________________________

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

h1

The Search for Acceleration, part 6, Australia

July 17, 2013

magnifying glass 145This is part 6 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 that could 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.

Australia

Australia has only 5 tide gauge stations with data sets that are at least 90% complete going back to 1960, but four of those go back to 1940 or earlier.  I will analyse this data in my usual way (detrend, weight, average, and derivative).

Regional sea level rise rates are usually swamped by things other than just global effects.  In the case of Australia we may be able to disentangle one of these effects – the El Nino Southern Oscillation.  I will also consider the component of the Australian sea level data that is orthogonal to the ENSO3.4 sea surface temperature.

The slide show shows my standard analyse.

This slideshow requires JavaScript.

ENSO

The El Nino Southern Oscillation dominates the sea level around Australia.  The following plot shows an overlay of the detrended weighted average of the five Australian tide gauge sites and the NINO3.4 index from the Hadley Centre.  I am including tide gauge data after 1915 which include at least two tide gauge sites at all times and no large data gaps.  The similarities are obvious.

ENSO sea level overlay

Let’s try to remove the ENSO effect from the sea level around Australia. I will do that by breaking the sea level data down into an 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.

orthogonal formula440

The top of each of the following slides shows the weighted, detrended, averaged Australian 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 of each slide shows the corresponding relative rise rates associated with sea level (white) and with the ENSO orthogonal component of the sea level (red).  Each successive slide shows the same original data with increasing Gaussian smoothing.

The most important thing to notice is that when the ENSO influence is removed the sea level rise rate at the end of the century is significantly reduced.

ENSO and global warming

If the higher relative rise rates at the end of the century are due to ENSO, then it is interesting to ask whether ENSO fluctuations are greater now (because of global warming?) than in the past.  The best answer to this question can be found in Highly Variable El Niño-Southern Oscillation Throughout the Holocene (Cobb, et. al., Science, 339, 1/4/13).

The abstract states…

Twentieth-century ENSO variance is significantly higher than average fossil coral ENSO variance but is not unprecedented. Our results suggest that forced changes in ENSO, whether natural or anthropogenic, may be difficult to detect against a background of large internal variability.

and the body of the paper mentions…

[T]he detection (and attribution) of any changes in ENSO properties would require very long time series spanning many centuries, to the extent that detection of such changes is even possible.

[M]uch of the observed differences in ENSO variance over the past 7 ky reflect strong internal variability… Relatively robust 20th-century ENSO variability may reflect a sensitivity to anthropogenic greenhouse forcing, but definitive proof of such an effect requires much longer data sets than are currently available, given the large range of natural ENSO variability implied by the available fossil coral data.

Conclusion

According to my usual analysis the rise rate at the end of the century was clearly higher than the average (from 1940 to present), but no higher than the 1940s.   Does the reconcile the satellite data and tide gauge data?  Yes.

But, when the part of the detrended sea level that is correlated to ENSO3.4 is removed, the remaining orthogonal part of the rise rate appears to be lower at the end of the century than during the 1940s, and not particularly high compared to the rest of the century. So if my removal of the ENSO effect is correct, then there was nothing “unusual” about the rise rate at the end of the century
_________________________________________

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

h1

The Search for Acceleration, part 5, The Netherlands

July 6, 2013

magnifying glass 145This is part 5 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 that could 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 global sea level rise rate is swamped by other effects.  In most locations the yearly rise and fall of the oceans is greater than the 18 cm of sea level rise during the entire 20th century.  Geologic effects (e.g. glacial isostatic adjustment or plate tectonics) add to local and regional rise rates, making them deviate greatly from the global rise rate.

I am working under the theory that by detrending sea level data from individual (local) sites and averaging with other regional sites it should be possible to extract changes in regional sea level rise rates while bypassing the question of what the “true” sea level rise rate is in that region.

The Netherlands

Netherlands elevation

Elevation and tide gauge locations for The Netherlands.

Nobody cares more about sea level rise than the folks in The Netherlands. They have been dealing with the issue long before anybody was worried about global warming, since 20% of the country’s area is below sea level.  They have excellent sea level data spanning nearly 150 years.  This map shows land elevations in the Netherlands as well as the location of seven high quality tide gauge stations.

Here is the PSMSL data for those seven locations…

Netherlands Raw Spread

Tide gauge data for the Netherlands.

As I have mentioned before, I am not concerned with finding the sea level rise rate, but rather the change in sea level rise rate. But this set of data averages out to have a 20th century rise rate very close to the commonly reported tide gauge derived average of 1.8 mm/year. (Click on image if animation does not advance.)

sea level annotated 450ani

These seven stations also have very coherent yearly signals, created from the 2, 3, 4, 6 & 12 month Fourier components.  Note that the magnitude of the yearly signal is nearly the same as the entire average sea level rise for the entire 20th century.

Netherlands Yearly signal

Now, lets consider the weighted, detrended data to derive the relative acceleration. (Click on image if animation does not work.)

Netherlands weighted and detrened 450ani

Conclusion

The Netherlands tide gauge data if of the highest quality and long duration.  All seven stations cover 1870 to the present.  The detrended sea level rise rate does indicate that the overall sea level rise rate for last two decades of the 20th century was a few mm per year greater than the century’s average.  However, this very reliable data also indicates that the sea level rise rate at the beginning of the century was just as high as the end of the century.

____________________________

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

h1

The Search for Acceleration, part 4: Mea Culpa

June 30, 2013

magnifying glass 145I had a big mistake in my last two posts…

The Search for Acceleration, part 2: East Coast of North America

and

The Search for Acceleration, part 3: Japan

The error caused my rise rate calculations to be off by a factor of 12! This was because I failed to account for the monthly increments in the RLR data.  This mistake caused large errors on my conclusions, which have now been corrected.

I use National Instruments LabVIEW software for all of my coding.  LabVIEW is an advanced graphical programming platform that makes it possible to write sophisticated code in a completely graphical environment.  That is, no lines of text as in the more traditional languages like Fortran or C.  Instead, various sub-programs (or “sub-VIs” in LabView parlance) can be wired together to create complex programs that would take much longer to write other languages.

The image below shows the mistake I made.  Mea Culpa.

LabView error

h1

The Search for Acceleration, part 2: East Coast of North America

June 24, 2013

magnifying glass 145

CORRECTION: 6/30/13

The original detrended sea level rise rate graphs for this post was off by a factor of 12!.  This greatly changes my conclusion.  Incorrect information is now crossed out and is followed by corrected information in red.

This is part 2 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 that could 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 global sea level rise rate is swamped by other effects.  In most locations the yearly rise and fall of the oceans is greater than the 18 cm of sea level rise during the entire 20th century.  Geologic effects (e.g. glacial isostatic adjustment or plate tectonics) add to local and regional rise rates, making them deviate greatly from the global rise rate.

I am working under the theory that by detrending sea level data from individual (local) sites and averaging with other regional sites it should be possible to extract changes in regional sea level rise rates while bypassing the question of what the “true” sea level rise rate is in that region.

East Coast of North America

Conclusion: There is no sign of an acceleration in the sea level rise rate in the tide gauge data from the East Coast of North America.

Conclusion:  The tide gauge data for the East Coast of North America that covers that satellite sea level data era (1993 to present) does show a rise rate that is significantly higher than the tide gauge data rise rate for the 20th century.  But the sea level rise rate in the 1930s through 1940s and around 1970 was as high or higher.Whether or not this data reconciles the difference between the 20th century tide gauge rise rate average and the satellite rise rate average is still ambiguous.

I have selected the East Coast of North America, for no particular reason, as the first region to analyse.  I looked for tide gauge data along the coast such that it covered at least the period from 1960 to 2008 with 90% of all monthly data accounted for.  Usable sites ranged from Nova Scotia to Georgia.

Click on any animations or graphs to enlarge.
East Coast North America 90p 1960-2008 Map

The following plot shows the qualifying data spread out for easy comparison.  The key at the right shows the associate RLR data files.

East Coast North America 90p 1960-2008 Raw Spread

Averaged data

As I mentioned above, I am not concerned with finding the sea level rise rate, but rather the change in sea level rise rate. However the following data for the East Coast of North America is interesting because it shows an averaged sea level rise rate for the 20th century that is close to the satellite derived sea rate for the end of the 20th century.  This is will not be the case for most regions around the world.  If you squint the right way you can also see the change in rise rate around 1930 that shows up in the various iterations of Church and White’s derivations of 20th century sea levels.

East Coast North America 90p 1960-2008 Avg 450ani2

Detrended data

East Coast North America 90p 1960-2008 450ani corrected

The last frame of the detrended data animation is worth repeating (see below).  Notice that there is no evidence of an extreme or consistent increase in the sea level rise rate in the last two decades.  The rise rates were as great or greater in the 1940s, 1950s and 1970s than they were in the 1980s, 1990s and 2000s.  However, at least part of the satellite era (1993 to present) tide gauge data may be more than 2 mm/year greater than the average for the 20th century.  It is safe to say that the tide gauge data from the East Coast of the North America does not reconcile the difference between the 20th century rise rate average (about 1.8 mm/year) and the satellite measured average (about 3 mm/year) Whether or not this data reconciles the difference between the 20th century tide gauge rise rate average and the satellite rise rate average is still ambiguous.

East Coast North America 90p 1960-2008 Detrended Acceleration
corrected East Coast North America 90p 1960-2008 Detrended Acceleration

Follow

Get every new post delivered to your Inbox.

Join 51 other followers