Comments on: Possible Error in OHC?

By: http://test.com

http://test.com — Mon, 15 Feb 2010 19:43:03 +0000

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By: Bob Tisdale

Bob Tisdale — Sun, 01 Nov 2009 22:34:08 +0000

Cohenite, the North Atlantic shows a long-term rise that appears to be caused in part by cycles in AMO/AMOC, but the South Atlantic has a more variability with a sudden upward shift in 2003.

By: cohenite

cohenite — Sun, 01 Nov 2009 21:27:33 +0000

So, the 'artifact' is mainly a factor of something in the Atlantic, predominantly the North Atlantic, data?

By: Bob Tisdale

Bob Tisdale — Sun, 01 Nov 2009 13:22:27 +0000

Here are some OHC spaghetti graphs for further discussion about the OHC shift in 2003. The first is the OHC from Jan 1955 to Jun 2009 for the North and South Atlantic, North and South Pacific, and the Indian Ocean. As you can see the biggest shift in 2003 takes place in the South Atlantic.
http://i38.tinypic.com/2q8xdu8.png

And here’s the same comparison of the major ocean basins with the data limited to Jan 2000 to Jun 2009.
http://i33.tinypic.com/w14u3n.png

Using the South Atlantic for reference, here’s a comparison of Arctic and Southern Oceans from Jan 1955 to Jun 2009. Both have sizeable increases but they appear to be part of a multiyear rises.
http://i37.tinypic.com/333v6zo.png

And here’s the same comparison of the South Pacific, Arctic and Southern Oceans with the data limited to Jan 2000 to Jun 2009.
http://i34.tinypic.com/311nspg.png

So the 2003 shift in the South Atlantic OHC seems to be the outlier. For this part of the post, I’ll borrow two graphs from my post “North Atlantic Ocean Heat Content (0-700 Meters) Is Governed By Natural Variables”:
http://bobtisdale.blogspot.com/2009/10/north-at...

The early 2000s rise in tropical South Atlantic OHC appears to lag the tropical North Atlantic by 1 to 2 years. Curious.
http://i34.tinypic.com/3532k5l.png

And the tropical North Atlantic seems to shift in response to the multiyear La Nina that followed the 1997/98 El Nino.
http://i38.tinypic.com/2jcbgvb.png

Now for two new graphs. The first is a comparison of the Low Latitude (25S-0) and Mid-To-High Latitude (60S-25S) South Atlantic from Jan 1955 to Jun 2009. The Mid-To-High Latitude OHC anomalies of the South Atlantic appear to mimic the tropical OHC anomalies, or vice versa, with the Mid-To-High Latitudes being noisier. Is the higher variability a result of the Southern Annual Mode, like the North Atlantic is impacted by the NAO? Dunno.
http://i37.tinypic.com/vqmsrd.png

And here’s the short-term version of the Low Latitude (25S-0) and Mid-To-High Latitude (60S-25S) South Atlantic OHC comparison.
http://i37.tinypic.com/1z3bif9.png

Is the 2003 OHC shift a natural effect? Is it a result of an overcorrection of ARGO biases? Dunno.

I’ll try to take a closer look at the Southern Ocean and Arctic Ocean OHC data soon.

By: Bob Tisdale

Bob Tisdale — Sun, 01 Nov 2009 08:09:39 +0000

David, sorry, I should have clarified my speculations above…that the 2003 rise would assumedly result from a lagged temporary shift in cloud cover. The rebound of tropical Pacific OHC during the recharge phase of ENSO is likely the result of atmospheric circulation changes, primarily cloud cover. What then happened to Hadley and Walker circulation, wind stress, cloud cover, etc., globally when the 1998/99/00 La Nina relaxed and ENSO conditions returned to neutral? Sorry, just thinking out loud. A three-year lag does seem excessive and unlikely.

By: davids99us

davids99us — Sun, 01 Nov 2009 01:32:50 +0000

Bob, Its not as large a change. The 2002-2003 change is the only event that large. As to the second question, you are suggesting a lower rate of heat increase leads to a higher rate of heat increase later on. It doesn't seem likely on themodynamic grounds, as impulse changes would normally be dissipating. But its not impossible is the smaller impulses are accumulating 'out of sight'. Hard to rule things out in a complex system.

By: Bob Tisdale

Bob Tisdale — Sun, 01 Nov 2009 01:27:27 +0000

David, would the 1997/98 El Nino represent the same type of statistical outlier since 1955? If the rise in 2003 is a residual effect of that El Nino, actually of the 2-year La Nina that followed it, would it then be that unusual? If that makes sense, the only thing left to determine is why there would be that long of a lag between the end of that multiyear La Nina and the OHC shift.

By: sherro

sherro — Sat, 31 Oct 2009 10:54:19 +0000

Where global measurements are involved, there is always a step where points data are converted to gridded data. This type of step is crucial in mining and has been studied deeply.

When you add satellite derived data, more and more "unusual" errors accumulate, so that difference maps will show artefacts. e.g. what was originally a surface grid with parallel, straight sides of latitude and curved sides of longitude assumes a different shape as the satellite altitude changes from drag and reburns, especially when the satellite view is inclined normal to the path. The sides of the grid cell can bulge in longitude and assume a "different" area that needs quite complex correction to both size and position.

It might be an interesting exercise to take watermelon slices, say 5 degrees apart in longitude, and compute their areas in the pole to equator quadrant, for different of the satellite and earth models. My hunch is that you will get different areas from different models at different times- especially when different satellites are used.

This might seem a bit OT, but you have to go through this process when calculating a global ocean heat content and a global ocean temperature. There is good reason to suspect that different organisations working on these data sets will produce different rsult, for reasons arising more from geometry than climate.

Currently, I'm sounding out some mining people for state of the art references to interpolation of point to grid and some surveying types on the godesy aspects of lat/long grids. In the fullness of time, I hope to have more to report.