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Monday, December 15, 2008

Sea Level Data: Global and Indian, Atlantic, and Pacific Oceans

I’ve moved to WordPress.  This post can now be found at Sea Level Data: Global and Indian, Atlantic, and Pacific Oceans
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INTRODUCTION

This post presents graphs of raw, smoothed, and annualized sea level data for Global, Indian Ocean, Atlantic Ocean, and Pacific Ocean data sets. The recently updated data is available through the University of Colorado at Boulder. Here’s a link to their Sea Level Change Overview (index) webpage:
http://sealevel.colorado.edu/index.php
and one to their Time Series Data Page:
http://sealevel.colorado.edu/results.php

In addition, graphs of the annual changes in sea level for those data sets are provided.

Note 1: You’ll note the graphs of the raw and smoothed data include the notation “Smoothed w/ 35-Period Filter”. The number of samplings varies per year, from 35 one year to 38 the next for example. Keep that in mind when viewing the data. To assure that the smoothing did not misrepresent the data, I’ve also presented the annual mean of the data sets in separate graphs.

Note 2: All of the data sets include the seasonal signals and they exclude the inverted-barometer adjustments.

GLOBAL SEA LEVEL

Figure 1 shows the Global Sea Level for the period of December 1992 to September 2008. Global Sea Level appears to have risen at a reasonably constant rate until mid-2005, when the rate of rise decreased.
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Figure 1

Looking at the annual data from 1993 to 2007, Figure 2, confirms the sharp deceleration in the rise of Global Sea Level in 2006 and 2007.
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Figure 2

Figure 3 illustrates the annual change in Global Sea Level from 1994 to 2007. With the exception of 2006, all values are above zero, indicating that Global Sea Levels are rising. However, the annual changes indicate that the there has been a decrease in the rate of rise over the term of the data. The curves of Global Sea Level, Figure 2 and 3, would not have flattened out if the rate of rise was accelerating.
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Figure 3

INDIAN OCEAN

The Indian Ocean Sea Level data is shown in Figure 4. Based on the smoothed data, the Indian Ocean Sea Level has not increased since early 2007. Also note the multiple swings in sea level during 1996 and 1997, leading up to the El Nino of 1997/98.
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Figure 4

Figure 5 illustrates the annual Indian Ocean Sea Level from 1993 to 2007. From 1999 to 2007, Indian Ocean Sea Level appears to have increased exponentially, but a look at the smoothed data in Figure 4 reveals that the rise has ended.
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Figure 5

Viewing the annual change in Indian Ocean Sea Level, Figure 6, reveals the significant rise in 1998 associated with the 1997/98 El Nino.
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Figure 6

ATLANTIC OCEAN

The raw and smoothed sea level data for the Atlantic Ocean is illustrated in Figure 7. The significant drop in 2002 does correspond to a sudden drop in Atlantic Ocean SST anomaly. (Refer to Figure 10 in Atlantic, Indian, and Pacific Ocean SSTs Segmented By Longitude.) Also, the Atlantic Ocean Sea Level does not appear to have risen significantly since 2005 based on the smoothed data.
http://i37.tinypic.com/2n6c1l5.jpg
Figure 7

This is confirmed by the annual Atlantic Ocean Sea Level data. Refer to Figure 8. Atlantic Ocean Sea Levels remained relatively flat in 2006, then dropped in 2007.
http://i34.tinypic.com/m7b994.jpg
Figure 8

The variability of the annual change in Atlantic Ocean Sea Level is illustrated in Figure 9.
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Figure 9

PACIFIC OCEAN

The smoothed sea level data for the Pacific Ocean, Figure 10, also appears to have flattened and decreased in recent years.

Note that in 1997 the peak in raw data of sea level (approximately June/July) preceded the El Nino peak, which occurred in October 1997 (not illustrated). And note the second large perturbation in late 2002/early 2003 that corresponds with the El Nino at that time.

It is unfortunate that the number and timing of sea level readings do not correspond with the weekly or monthly values presented for SST so that comparative graphs of Pacific Sea Level versus Pacific and NINO3.4 SST anomalies could be presented. It would be interesting to compare the timing of the rises and falls in the different data sets.
http://i34.tinypic.com/28hk7j6.jpg
Figure 10

Figure 11 illustrates the annual Pacific Ocean Sea Level data from 1993 to 2007. The impacts of the 1997/98 El Nino and subsequent multiyear La Nina are visible, as are the rise in 2002 and fall in 2003, which no longer appear disproportionate. Note that the Pacific Ocean Sea Level peaks in 2005 and has fallen in 2006 and 2007.
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Figure 11

Figure 12 illustrates the annual changes in Pacific Ocean Sea Level and SST anomaly.
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Figure 12

CLOSING NOTE

Thanks to Bill Illis for noting the flattening of the Pacific and Atlantic Ocean Sea Level curves in a comment on an earlier thread.

SOURCES

The source of the sea level data is discussed in the Introduction.

3 comments:

climatechange1 said...

This is very intereting. I wish their data extended further into the past. Any idea about how well we can consider sea level as a proxy for ocean heat content?

climatechange1 said...

I've found an extremely useful website.
http://sealevel.colorado.edu/wizard.php?dlon=146&dlat=21&map=t&fit=s&smooth=n&days=60&coor.x=195&coor.y=100

Carl

Anonymous said...

The sea level data is colloected by high precision satellite altimeters that have been in operation since 1992.

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