Atlantic Meridional Overturning Circulation Data

I’ve moved to WordPress.  This post can now be found at Atlantic Meridional Overturning Circulation Data

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UPDATE

I believe this is the paper that describes the data set:
http://hal.inria.fr/docs/00/18/17/39/PDF/GRL_MOC_submit3.pdf

INTRODUCTION

In their Climate Indices webpage, the Royal Netherlands Meteorological Institute (KNMI) has an interesting historical data set available for downloading: Atlantic Meridional Overturning Circulation (AMOC).

KNMI website:
http://www.knmi.nl/about_knmi/
Climate Indices webpage:
http://climexp.knmi.nl/selectindex.cgi?someone@somewhere
ORA-S3, MOC [Sv] Meridional Overturning Circulation at 26N webpage:
http://climexp.knmi.nl/getindices.cgi?ECMWFData/AtlanticMOC26N+AMOC_ecmwf_S3+i+someone@somewhere
MOC Data in text form:
http://climexp.knmi.nl/data/iAtlanticMOC26N.dat

The monthly data set begins in January 1961 and ends in December 2005. The units are Sverdrup (Sv), where 1 Sv is equal to a volume flow rate of 10^6 cubic meters per second. The notation “ORA-S3” at the top of the data page indicates the source, which is the European Centre for Medium-Range Weather Forecasts (ECMRF). Their webpage:
http://www.ecmwf.int/
Chasing the data set farther, the ECMRF’s ORA-S3 System is described beginning on page 9 of their Autumn 2007 newsletter:
http://www.ecmwf.int/publications/newsletters/pdf/113.pdf

Enough with the background.

ATLANTIC MERIDIONAL OVERTURNING CIRCULATION DATA

Figures 1 and 2 illustrate the Atlantic Meridional Overturning Circulation (AMOC) Data from January 1961 to December 2005. In Figure 1, the data is raw. The data has been smoothed with a 12-month running average filter in Figure 2 to remove the monthly noise. At first glance, the graph of the data set doesn’t appear similar to any other data I’ve run across to date, and the 1972 spike does not to correlate with any of the usual suspects: volcanic aerosols or ENSO.


http://i33.tinypic.com/2vxlj44.jpg
Figure 1
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http://i38.tinypic.com/s6lhzc.jpg
Figure 2

The representation of AMOC bears no resemblance to the AMO. Refer to Figure 3.
http://i33.tinypic.com/viji95.jpg
Figure 3

The AMOC curve does not appear to have a basis in the High Latitude North Atlantic SST anomalies, Figure 4. Since that’s the area of AMOC subsidence, it seemed possible there might be a correlation. There’s not.
http://i34.tinypic.com/2ryjxtx.jpg
Figure 4

Maybe we need to change the appearance.

INVERTED ATLANTIC MERIDIONAL OVERTURNING CIRCULATION DATA

In Figure 5, the AMOC data has been inverted (multiplying it by -1). There are times when the inverted AMOC data may correlate with ENSO.
http://i36.tinypic.com/awqkyf.jpg
Figure 5

Figure 6 is a comparative graph of Inverted AMOC and NINO3.4 SST anomalies. I have not scaled the NINO3.4 data. I simply shifted it, changing its temperature range. Prior to 1977, there seems to be no correlation between NINO3.4 and Inverted AMOC. But, from the early 1977 to present, they correlate very well, with the exceptions of in-phase then out-of-phase response to the 1997/98 El Nino. What took place just before 1977? The Great Pacific Climate Shift of 1976.

Keep in mind that the AMOC data has been inverted in Figure 6 and that it illustrates that an increase in NINO3.4 SST anomaly causes a decrease in AMOC flow during most ENSO events from 1977 to present.
http://i33.tinypic.com/5cyglz.jpg
Figure 6

SOURCES

The source of the AMOC data is discussed in the Introduction of this post.

The Smith and Reynolds Extended Reconstructed SST (ERSST.v2) data is available through the NOAA National Operational Model Archive & Distribution System (NOMADS).http://nomads.ncdc.noaa.gov/#climatencdc

NINO3.4 Data Comparison – HADSST and ERSST.v2

INTRODUCTION

In a previous post “Standardized versus Raw (Not Standardized) NINO3.4 SST Anomaly Data” (11/13/08), which I have removed, I mistakenly attributed the differences between the two data sets to standardization. The standardized NINO3.4 SST anomaly data that I used in that post was prepared by Trenberth and Stepaniak. Trenberth and Stepaniak discuss their NINO3.4 index and its recipe here:
http://www.cgd.ucar.edu/cas/catalog/climind/TNI_N34/index.html#Sec5
Their updated 1871 to 2007 NINO3.4 data is here:
ftp://ftp.cgd.ucar.edu/pub/CAS/TNI_N34/Nino34.1871.2007.txt
Investigating the source of the Trenberth and Stepaniak NINO3.4 SST data further, it’s based on Hadley Centre HADSST data, which is available through the NCDC:
http://www.cdc.noaa.gov/Pressure/Timeseries/Data/nino34.long.data
The reference to HADSST is at the bottom of that webpage. The HADSST source is confirmed by the NCDC discussion page:
http://www.cdc.noaa.gov/Pressure/Timeseries/Nino34/

With the background of this post complete, there are underlying differences between the HADSST and ERSST.v2 NINO3.4 SST data, with the most significant differences occurring before the mid-20th Century.

There are also small and subtle differences depending on whether the NINO3.4 anomaly data has been standardized or left in its raw state. For this reason, I’ve illustrated it both ways in the following. But first, there’s the…

DIFFERENCE IN SST DATA

Figure 1 compares the HADSST and ERSST.v2 versions of NINO3.4 SST (not anomaly) data. The two track well from the mid-1950s to present. Prior to that, they diverge and the differences can be substantial.

http://i33.tinypic.com/orl1tc.jpg
Figure 1

Figure 2 illustrates the difference between the ERSST.v2 and HADSST versions of NINO3.4 SST, where the ERSST.v2 data was subtracted from the HADSST data. The difference indicates there is an underlying trend in the SST data of the ERSST.v2 version that doesn’t appear in the HADSST data.
http://i38.tinypic.com/20zw7bb.jpg
Figure 2

DIFFERENCE IN SST ANOMALY DATA

Figures 3 and 4 provide comparisons that are similar to the above, but in these graphs, SST anomaly data are compared. The same base years were used for both data sets, 1950 to 1979, which are those used in the referenced Trenberth and Stepaniak data. The comparisons of SSTs and SST anomalies are very similar.
http://i37.tinypic.com/okpfs8.jpg
Figure 3
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http://i34.tinypic.com/1585i6t.jpg
Figure 4

DIFFERENCE IN STANDARDIZED SST ANOMALY DATA

In Figures 5 and 6, I took the process one step farther and compared standardized versions of the ERSST.v2 and HADSST NINO3.4 data. There are subtle differences between the raw and standardized data sets, though you’d have to flip between the images to see them. The most obvious is that the variations have been exaggerated by the standardization process. This can be seen by comparing the temperature scales and the peaks of the major El Nino events.

A note about the standardization used: I followed the recipe given by Trenberth and Stepaniak in the first link above, with the following exception: I did NOT smooth the data with a 5-month filter prior to normalization.
http://i33.tinypic.com/2dl2lie.jpg
Figure 5
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http://i34.tinypic.com/5cllxk.jpg
Figure 6

CLOSING COMMENT

In the earlier post that I’ve just deleted, I had included graphs of the Trenberth and Stepaniak NINO3.4 data for use as references. The following are those graphs. The data in Figure 7 has not been filtered by me. Figures 8 and 9 have been smoothed, with 12- and 25-month filters.
http://i36.tinypic.com/vq5y83.jpg
Figure 7
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http://i33.tinypic.com/8zha43.jpg
Figure 8
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http://i38.tinypic.com/10nxs84.jpg
Figure 9

SOURCES

The source of the HADSST data is discussed in the introduction, above.

The Smith and Reynolds Extended Reconstructed SST (ERSST.v2) data is available through the NOAA National Operational Model Archive & Distribution System (NOMADS).http://nomads.ncdc.noaa.gov/#climatencdc

The reasons for smoothing ENSO-related data with a 25-month filter are discussed here:
http://bobtisdale.blogspot.com/2008/11/different-way-to-look-at-nino34-data.html

For Example, Bob Tisdale Commented...

UPDATE (2-19-09): And yet another website attributing this comment to me. MacCompanion:
http://www.maccompanion.com/macc/archives/November2008/Greenware/GlobalCooling.htm
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Being misquoted is one thing, having a thoughtful comment by another blogger attributed to me is another.

I discovered on a number of blogs that I was said to have made the following comment:
"If the Antarctic is getting warmer, as claimed, than (sic) why has the ice cover there increased by far more than that 'lost' at the arctic? 

If the arctic is loosing (sic) ice at an 'increasing rate', than why has this year seen record early ice formation and record extent? 

If the earth is getting warmer, than why have record low temperatures and record early snowfalls been occurring across the Northern hemisphere this year (and temperatures becoming lower for the last 5 years)?"

An example from the Pure Energy Systems (PesWiki) site:
http://peswiki.com/index.php/Directory:Global_Cooling

I haven’t taken the time to track down who made the error first, but the above quote is part of comment made by Abigail at the Telegraph.co.UK website on their thread titled “Man is to blame for Antarctic temperature rise”.
http://www.telegraph.co.uk/earth/earthnews/3354073/Man-is-to-blame-for-Antarctic-temperature-rise.html

My comment was immediately before hers and it read:

Here are two graphs of temperature data that contradict the claims made in the article. The first is a graph of global, Northern Hemisphere, and Arctic land and sea surface temperature anomalies. Note how the Arctic temperature diverges from the global and Northern Hemisphere data after the 97/98 El Nino. Arctic temperatures then remain at the elevated level due to the influence of the subsequent El Nino events that occurred in 2002/03, 2004/05, and 2006/07. Arctic warming in response to El Nino events is consistent with the projections of coupled GCMs.
http://i34.tinypic.com/2cxasl3.jpg

The second graph is of the Sea Surface Temperature (SST) anomalies for the Southern Ocean, which is the ocean that surrounds the Antarctic. I fail to find an anthropogenic warming signal in that data. In fact, Southern Ocean SST anomalies have been decreasing since the 1980s. How does that agree with the claims made in the article?
http://i37.tinypic.com/315bzad.jpg

Sources:

http://bobtisdale.blogspot.com/2008/07/polar-amplification-and-arctic-warming.html
http://bobtisdale.blogspot.com/2008/09/ersstv3-version-of-southern-ocean-sst.html

Have a nice day.

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To those who made the mistake: please correct your attribution.

Sorry to steal your thunder, Abigail. I hope this corrects the problem.

Regards