OHC Linear Trends and Recent Update of NODC OHC (0-700 Meters) Data

I’ve moved to WordPress.  This post can now be found at OHC Linear Trends and Recent Update of NODC OHC (0-700 Meters) Data

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The National Oceanographic Data Center (NODC) presented its Ocean Heat Content (OHC) data in conjunction with the Levitus et al (2009) Paper. The NODC makes the data available to the public and maintains it at their GLOBAL OCEAN HEAT CONTENT webpage. About January 20, 2010, the NODC added its 4th quarter and annual 2009 OHC data so that it covered the period of 1955 to 2009. On January 29 and February 1, 2010, the NODC also updated its 2006-and-later data. The KNMI Climate Explorer was updated in response to the 4th quarter NODC OHC additions and, on February 1, to the 2006-and-later revisions. (Thanks to Tim and Geert Jan for the timely updates.)

This post presents:
1. A brief look at impact of the revisions (corrections) to the 2006-and-later OHC data
2. OHC Trend Comparisons for individual ocean basins and hemispheres
3. An update of the global, hemispheric, and basin OHC data through December 2009

A Note About The Data Presented In This Post: This data used in the graphs (except Figure 2) was downloaded through the KNMI Climate Explorer website, which allows users to define the coordinates of the desired data subset. The data is presented in Gigajoules per square meter (GJ/m^2), not in 10^22 Joules like the NODC. In the GJ/m^2 format, subsets are easier to compare, since adjustments for surface area do not have to be made (they’ve already been made). The NODC presents quarterly data. KNMI includes those quarterly values for each corresponding month. This “squares off” the monthly data in the graphs, since the one value is the same for three consecutive months, but it permits comparisons to other monthly datasets, such as NINO3.4 SST anomalies.

REVISIONS (Corrections) TO THE 2006-AND-LATER NODC OHC DATA
I provided a quick introduction to the revisions (corrections) to the 2006-and-later OHC data in my recent post NODC Ocean Heat Content (0-700 Meters) - 2007, 2008 & 2009 Corrections. In that post, I had not noticed that the 2006 data had also been revised.

Figure 1 is a time-series graph of the updated and revised Global OHC data. The cell in the upper right-hand corner shows an earlier version, before the revisions to the 2006-and-later data. I have found nothing in the NODC OHC web pages that discuss these new corrections. Are they more corrections for ARGO biases?
http://i49.tinypic.com/jpetf4.png
Figure 1

The revisions to the 2006-and-later data shown in Figure 1 had little impact on the overall rise in the data since 1955. To confirm this, as illustrated in Figure 4 of this post, the linear trend of the revised and updated data for January 1955 through December 2009 is 0.078 GJ/meter^2/ decade. Before the revisions to the 2006-and-later data, the linear trend for the same period (not shown) was 0.079 GJ/meter^2/ decade.

-HOWEVER-
The revisions to the recent data do impact the trend of the short-term data used to illustrate the divergence between the observations and the GISS projections. This was discussed in the post NODC Ocean Heat Content (0-700 Meters) Versus GISS Projections (Corrected). In a communication with Roger Pielke Sr., James Hansen of GISS predicted an OHC accumulation of approximately 0.98*10^22 Joules per year. But the trend of the current version of the NODC OHC data (the observations) is approximately 1.5% of that GISS projection. That is, GISS projected a significant rise, while the observations have flattened significantly in recent years. The reasons for the divergence between observations and the GISS Projection were discussed in Why Are OHC Observations (0-700m) Diverging From GISS Projections? In short, GISS appears to have based its projection on the rise in OHC from the early 1990s to the early 2000s, assuming the rise was caused by changes in manmade factors and that the effect of those anthropogenic forcings would continue unabated into the future. But GISS failed to consider that the vast majority of the rise during the early 1990s to the early 2000s was caused by natural variables such as El Nino/La Nina events, the North Atlantic Oscillation, and the like, not by manmade forcings.
http://i47.tinypic.com/20kvhwn.png
Figure 2

The earlier version of that graph…
http://i37.tinypic.com/i6xtnl.png
…shows a linear trend of ~0.08*10^22 Joules/year. The current linear trend is ~0.015*10^22 Joules/year.

TREND COMPARISONS
In the numerous posts on the NODC OHC data that precede this one, I don’t believe I’ve presented linear trend comparisons. Looking at the OHC linear trends for the individual ocean basins, Figure 3, it is very evident that the North Atlantic played a major role in the rise of global OHC since the early-to-mid 1970s. The linear trends of the OHC for most ocean basins, excluding the North and South Atlantic, are between 0.047 and 0.066 GJ/meter^2/decade. The linear trend of the North Atlantic OHC (0.205 GJ/meter^2/decade), on the other hand, is approximately 3 to 4 times those values. The South Atlantic OHC trend falls in between, suggesting an influence of the North Atlantic on the South Atlantic.
http://i50.tinypic.com/2eexa8w.png
Figure 3

BIG IFS
IF the multi-decade variations in North Atlantic OHC are similar in timing to the AMO, and IF the AMO did peak in 2005, and IF (lots of big IFs) the decline in North Atlantic OHC persists for another two plus decades, will global OHC continue to remain flat (or decline) for that long, too? Many of the other ocean basins are showing recent flattening or declines, so the North Atlantic is not alone. Regardless, a long-term decline in North Atlantic OHC (if one were to occur) would definitely not help long-term projections of a monotonous rise in OHC. And since the only variables that appear to cause significant rises in the other ocean basins are multiyear La Nina events and shifts in sea level pressure, a continued drop in North Atlantic OHC would have to be counteracted by one of those other factors.

The following are links to earlier posts that illustrate and discuss how natural variables (including ENSO events and changes in sea level pressure as represented by the North Atlantic Oscillation and North Pacific Index) are responsible for most of the rise in OHC since 1955:
ENSO Dominates NODC Ocean Heat Content (0-700 Meters) Data,
AND
North Atlantic Ocean Heat Content (0-700 Meters) Is Governed By Natural Variables,
AND
North Pacific Ocean Heat Content Shift In The Late 1980s

Figures 4 through 6 are comparison graphs of global and hemispheric OHC linear trends and the OHC linear trends for the individual ocean subsets per hemisphere.
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Figure 4
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http://i48.tinypic.com/n5qzw5.png
Figure 5
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http://i46.tinypic.com/o9k9at.png
Figure 6
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GLOBAL, HEMISPHERIC, AND INDIVIDUAL BASIN OHC UPDATE THROUGH DECEMBER 2009
For those who enjoy information overload, the following are time-series graphs of OHC data (0-700 meters) for the globe, hemispheres, and the individual ocean basins.

Note: I have no plans to perform comparisons of the data for the individual basin OHC anomalies before and after the revisions to the 2006-and-later data. I have compared the graphs I have on file, and the revisions do appear to have impacted all ocean basins. For those who wish to confirm this, you would have to download all of the following graphs, and also download the graphs from the post Update NODC (Levitus et al 2009) OHC Data Through June 2009 (Corrected). The color coding for the ocean basins have remained the same, with the exception of the Southern Ocean. The sizes of the images may vary slightly, but the corrections are still visible.

One last note: As opposed to presenting the OHC for the NINO3.4 region of the equatorial Pacific, I’ve included Tropical Pacific OHC data in the update. Here are graphs of the updated data without commentary:
http://i47.tinypic.com/5vuart.png
Figure 7 - Global OHC
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http://i50.tinypic.com/33ys42h.png
Figure 8 - Northern Hemisphere OHC
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http://i46.tinypic.com/2krfps.png
Figure 9 - Southern Hemisphere OHC
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http://i49.tinypic.com/2nut183.png
Figure 10 – Tropical Pacific OHC
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http://i45.tinypic.com/nvtgef.png
Figure 11 - North Atlantic OHC
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http://i45.tinypic.com/9pp4rq.png
Figure 12 - South Atlantic OHC
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http://i45.tinypic.com/jpc3l3.png
Figure 13 - North Pacific
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http://i50.tinypic.com/qof4wk.png
Figure 14 - South Pacific
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http://i49.tinypic.com/2ihxm6r.png
Figure 15 - Indian Ocean
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http://i48.tinypic.com/n3rb47.png
Figure 16 - Arctic Ocean
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http://i50.tinypic.com/1236qlt.png
Figure 17 - Southern Ocean

SOURCES
NODC Annual Global OHC data used in Figure 2 is available here:
ftp://ftp.nodc.noaa.gov/pub/data.nodc/woa/DATA_ANALYSIS/3M_HEAT_CONTENT/DATA/basin/yearly/h22-w0-700m.dat

The other graphs of NODC OHC data were created from data provided by the KNMI Climate Explorer website:
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere