April to June 2011 NODC Ocean Heat Content Anomalies (0-700Meters) Update and Comments

A NEW APPEARANCE

Due to the noise in the Ocean Heat Content anomaly data for some of the ocean basins, I’ve added 13-month running average filters to the long-term graphs.

SAME INTRODUCTION AS ALWAYS

The National Oceanographic Data Center’s (NODC) Ocean Heat Content (OHC) anomaly data for the depths of 0-700 meters are available through the KNMI Climate Explorer Monthly observations webpage. The NODC OHC dataset is based on the Levitus et al (2009) paper “Global ocean heat content (1955-2008) in light of recent instrumentation problems”. Refer to Manuscript. It was revised in 2010 as noted in the October 18, 2010 post Update And Changes To NODC Ocean Heat Content Data. As described in the NODC’s explanation of ocean heat content (OHC) data changes, the changes result from “data additions and data quality control,” from a switch in base climatology, and from revised Expendable Bathythermograph (XBT) bias calculations.

The OHC anomaly data is provided from the NODC on a quarterly basis. There it is available globally and for the ocean basins in terms of 10^22 Joules. The KNMI Climate Explorer presents the quarterly data on a monthly basis. That is, the value for a quarter is provided for each of the three months that make up the quarter, which is why the data in the following graphs appear to have quarterly steps. Furnishing it in a monthly format allows one to compare the OHC data to other datasets that are available on a monthly basis. The data is also provided on a Gigajoules per square meter (GJ/m^2) basis through the KNMI Climate Explorer, which allows for direct comparisons of ocean basins, for example, without having to account for surface area.

This update includes the data through the quarter of April to June 2011.

Let’s start the post with a couple of looks at the ARGO-era OHC anomalies.

BASIN TREND COMPARISONS

Figure 1 and 2 compare OHC anomaly trends for the ocean basins, with the Atlantic and Pacific Ocean also divided by hemisphere. Figure 1 shows the ARGO-era data, starting in 2003, and Figure 2 covers the full term of the dataset, 1955 to present. The basin with the greatest short-term ARGO-era trend is the Indian Ocean, but it has a long-term trend that isn’t exceptional. (The green Indian Ocean trend line is hidden by the dark blue Arctic Ocean trend line in Figure 2.) The basin with the greatest rise since 1955 is the North Atlantic, but it also has the largest drop during the ARGO-era. Much of the long-term rise and the short-term flattening in Global OHC are caused by the North Atlantic. If the additional long-term rise and the recent short-term decline in the North Atlantic OHC are functions of additional multidecadal variability similar to the Atlantic Multidecadal Oscillation, how long will the recent flattening of the Global OHC persist? A couple of decades?

Note also in the ARGO-era graph, Figure 1, that the South Atlantic and Indian Ocean subsets are the only ocean basins with positive linear trends. The sharp decline in the North Pacific OHC anomalies during the second quarter 2011 was great enough to drop its ARGO-era trend to just below zero.

Figure 1

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Figure 2

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Further discussions of the North Atlantic OHC anomaly data refer to North Atlantic Ocean Heat Content (0-700 Meters) Is Governed By Natural Variables. And if you’re investigating the impacts of natural variables on OHC anomalies, also consider North Pacific Ocean Heat Content Shift In The Late 1980s and ENSO Dominates NODC Ocean Heat Content (0-700 Meters) Data.

ARGO-ERA MODEL-DATA COMPARISON

Much of the discussion under this heading was first presented in the post January to March 2011 NODC Ocean Heat Content (0-700Meters) Update and Comments.I’ve attempted to clarify some of the points in this version.

Many of you will recall the discussions generated by the simple short-term comparison graph of the GISS climate model projection for global OHC versus the actual observations, which are comparatively flat. The graph is solely intended to show that since 2003 global ocean heat content (OHC) anomalies have not risen as fast as a GISS climate model projection. Tamino, after seeing the short-term model-data comparison graph in a few posts, wrote the unjustified Favorite Denier Tricks, or How to Hide the Incline. I responded with On Tamino’s Post “Favorite Denier Tricks Or How To Hide The Incline”. And Lucia Liljegren joined the discussion with her post Ocean Heat Content Kerfuffle. Much of Tamino’s post had to do with my zeroing the model-mean trend and OHC data in 2003.

While preparing the post GISS OHC Model Trends: One Question Answered, Another Uncovered, I reread the paper that presented the GISS Ocean Heat Content model: Hansen et al (2005), “Earth’s energy imbalance: Confirmation and implications”.Hansen et al (2005) provided a model-data comparison graph to show how well the model matched the OHC data. Figure 3 in this post is Figure 2 from that paper. As shown, they limited the years to 1993 to 2003 even though the NODC OHC data starts in 1955. Hansen et al (2005) chose 1993 as the start year for three reasons. First, they didn’t want to show how poorly the models hindcasted the early version of the NODC OHC data in the 1970s and 1980s. The models could not recreate the hump that existed in the early version of the OHC data. Second, at that time, the OHC sampling was best over the period of 1993 to 2003. Third, there were no large volcanic eruptions to perturb the data. But what struck me was how Hansen et al (2005) presented the data in their time-series graph. They appear to have zeroed the model ensemble mean and the observations at 1993.5. The very obvious reason they zeroed the data then was so to show how well OHC models matched the data from 1993 to 2003.

Figure 3

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The ARGO-era model-data comparison graph in this post, Figure 4, is also zeroed at the start year, 2003, but I’ve done that to show how poorly the models now match the data. I’m not sure why my zeroing the data in 2003 is so difficult for some people to accept. Hansen et al (2005) zeroed at 1993 to show how well the models recreated the rise in OHC from 1993 to 2003, but some bloggers attempt to criticize my graphs when I zero the data in 2003 to show how poorly the models match the data after that. The reality is, the flattening of the Global OHC anomaly data was not anticipated by those who created the models. This of course raises many questions, one of which is, if the models did not predict the flattening of the OHC data in recent years, much of which is based on the drop in North Atlantic OHC, did the models hindcast the rise properly from 1955 to 2003? Apparently not. This was discussed further in the post Why Are OHC Observations (0-700m) Diverging From GISS Projections?

Figure 4 compares the ARGO-era Ocean Heat Content observations to the model projection, which is an extension of the linear trend determined by Hansen et al (2005), for the period of 1993 to 2003. Over that period, the modeled OHC rose at 0.6 watt-years per year. I’ve converted the watt-years to Gigajoules using the conversion factor readily available through Google: 1 watt years = 31,556,926 joules. With the recent seasonal declines in Global Ocean Heat Content anomalies, the model projection is rising at a rate that’s more than 10 times higher than the observations since 2003. 10 times higher.

Figure 4

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HOW LONG UNTIL THE MODELS ARE SAID TO HAVE FAILED?

I asked the question in Figure 4, If The Observations Continue To Diverge From The Model Projection, How Many Years Are Required Until The Model Can Be Said To Have Failed? I raised a similar question in the post 2nd Quarter 2011 NODC Global OHC Anomalies last week, and in the WattsUpWithThat cross post Global Ocean Heat Content Is Still Flat, a blogger stated, in effect, that 8 ½ years was not long enough to reject the models.If we scroll up to Figure 3, Figure 2 from Hansen et al (2005), we can see that Hansen et al (2005) used only 11 years to confirm their Model E hindcast was a good match for the Global Ocean Heat Content anomaly observations. Can we then assume that the same length of time will be long enough to say the model has failed during the ARGO era?

And as noted in OHC update from last quarter, it’s really a moot point. Hansen et al (2005) shows that the model mean has little-to-no basis in reality. They describe their Figure 3 (provided here as Figure 5 in modified form) as, “Figure 3 compares the latitude-depth profile of the observed ocean heat content change with the five climate model runs and the mean of the five runs. There is a large variability among the model runs, revealing the chaotic ‘ocean weather’ fluctuations that occur on such a time scale. This variability is even more apparent in maps of change in ocean heat content (fig. S2). Yet the model runs contain essential features of observations, with deep penetration of heat anomalies at middle to high latitudes and shallower anomalies in the tropics.” I’ve deleted the illustrations of the individual model runs in Figure 5 for an easier visual comparison of the graphics of the observations and the model mean. I see no similarities between the two. None.

Figure 5

GLOBAL

The Global OHC data through June 2011 is shown in Figure 6. It continues to be remarkably flat since 2003, especially when one considers the magnitude of the rise that took place during the 1980s and 1990s from 1983 through 2003.

Figure 6

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TROPICAL PACIFIC

Figure 7 illustrates the Tropical Pacific OHC anomalies (24S-24N, 120E-90W). The major variations in tropical Pacific OHC are related to the El Niño-Southern Oscillation (ENSO). Tropical Pacific OHC drops during El Niño events and rises during La Niña events. As discussed in the update for October to December 2010, the Tropical Pacific had not as of then rebounded as one would have expected during the 2010/11 La Niña event. It finally responded a little during the first quarter of 2011, but with the drop during the most recent quarter, it appears the 2010/11 La Niña event did little to recharge the heat discharged during the 2009/10 El Nino.

Figure 7

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For more information on the effects of ENSO on global Ocean Heat Content, refer to ENSO Dominates NODC Ocean Heat Content (0-700 Meters) Data and to the animations in ARGO-Era NODC Ocean Heat Content Data (0-700 Meters) Through December 2010.

A CHANGE IN THE COORDINATES USED FOR THE NORTH ATLANTIC

I recently changed the coordinates I use for the North Atlantic in the Sea Surface Temperature anomaly updates from 0-75N, 78W-10E to 0-70N, 80W-0. I did this so that I was using the same coordinates the that NOAA/ESRL uses for their Atlantic Multidecadal Oscillation (AMO) data. I’ve now changed the coordinates I’m using in the OHC updates to 0-70N, 80W-0 for consistency between datasets. There is little difference in the OHC anomalies between the old and new coordinates as shown in Figure 8.

Figure 8

THE HEMISPHERES AND THE OCEAN BASINS

The following graphs illustrate the long-term NODC OHC anomalies for the Northern and Southern Hemispheres and for the individual ocean basins–without commentary.

(9) Northern Hemisphere

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(10) Southern Hemisphere

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(11) North Atlantic (0 to 70N, 80W to 0)

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(12) South Atlantic (0 to 60S, 70W to 20E)

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(13) North Pacific (0 to 65N, 100 to 270E, where 270E=90W)

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(14) South Pacific (0 to 60S, 120E to 290E, where 290E=70W)

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(15) Indian (60S-30N, 20E-120E)

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(16) Arctic Ocean (65 to 90N)

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(17) Southern Ocean (60 to 90S)

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AN ANIMATED COMPARISON OF OCEAN BASIN OHC ANOMALIES

I was recently asked why I did not use one scale for the y-axis in graphs of the ocean basins—that having the scale change for each basin made it difficult to compare graphs. The answer: because the rise in North Atlantic OHC anomalies is so much greater than the other ocean basins, the scale required for it skews the scaling for the other ocean basins. But for those interested, Animation 1 illustrates the OHC anomalies for each of the ocean basins, while keeping a common scale for the y-axis.

Animation 1

SOURCE

All data used in this post is available through the KNMI Climate Explorer:

http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere