>There Are Also El Nino-Induced Step Changes In The North Atlantic

>While preparing the January 2009 SST Anomaly Update post, the step changes in the North Atlantic SST anomaly dataset stood out clearly. Refer to Figure 1.
http://i43.tinypic.com/6f72ol.jpg
Figure 1

The bases for and processes that contributed to the step changes in the East Indian and West Pacific SST are discussed in:
Can El Nino Events Explain All of the Global Warming Since 1976? – Part 1
Can El Nino Events Explain All of the Global Warming Since 1976? – Part 2
Supplement To “Can El Nino Events Explain All Of The Warming Since 1976?”
Supplement 2 To “Can El Nino Events Explain All Of The Warming Since 1976?”
The processes would be different in the North Atlantic, but the effects are similar. Refer to Figure 2, which compares North Atlantic SST anomalies to scaled NINO3.4 SST anomalies. The NINO3.4 data has not been scaled to illustrate cause and effect. It is provided for timing purposes only.
http://i39.tinypic.com/z7juc.jpg
Figure 2

Using the Sato Index of Stratospheric Aerosols as a reference for timing also, Figure 3, it’s clear that the El Chichon (1982) and Mount Pinatubo (1991) eruptions disrupted the normal heat distribution of the 1982/83 and 1991/92 El Nino events and prevented the step changes at those times.
http://i43.tinypic.com/2ezsk92.jpg
Figure 3

COMPARISON TO EAST INDIAN-WEST PACIFIC SST ANOMALIES

Figure 4 is the short-term (OI.v2 SST-based) comparison of North Atlantic and East Indian-West Pacific SST anomalies from November 1981 to December 2008. The magnitudes of the two major steps are similar in scale, but there are differences in the reactions to the two volcanic eruptions. Also, the two datasets diverge after the 2002/03 El Nino, when the North Atlantic SST anomalies continue to rise. The North Atlantic SST anomalies do appear to be decreasing with time, though.
http://i39.tinypic.com/15cocop.jpg
Figure 4

I am not implying that the El Nino-induced step changes are the only contributors to North Atlantic SST variability, but they do impact it significantly. If we compare the North Atlantic and the East Indian-West Pacific SST anomalies from 1880 to present (ERSST.v2 data smoothed with 12-month filter), Figure 5, the additional impacts of Thermohaline Circulation/Meridional Overturning Circulation on the North Atlantic are also visible.
http://i43.tinypic.com/dxk01l.jpg
Figure 5

Note: Recallthat the Atlantic Meridional Overturning Circulation appears to be impacted by ENSO events as well. Refer to the post titled Atlantic Meridional Overturning Circulation Data.

THE REST OF THE OCEAN DATA (BETWEEN 60S and 65N)

With a coordinate-based system, to eliminate overlap and minimize the areas missed, the SST anomalies of the remainder of the oceans between 60S and 65 N (not included in the North Atlantic or the East Indian-West Pacific SST anomalies) had to be subdivided into three subsets:
-Northeast Pacific [0-65N, 180W-90W], Figure 6,
-Southeast Pacific-South Atlantic [60S-0, 180W-20E], Figure 7, and
-West Indian Ocean, [60S-30N, 20E-80E], Figure 8.

While there are short-term divergences, the other global ocean SST anomaly subsets follow NINO3.4 SST anomalies well.
http://i39.tinypic.com/2z5kkmh.jpg
Figure 6
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http://i39.tinypic.com/2ivehp3.jpg
Figure 7
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http://i40.tinypic.com/rwmers.jpg
Figure 8

CLOSING COMMENT

In addition to the EL Nino-induced step changes witnessed in the East Indian and West Pacific oceans, the step changes in the North Atlantic also contradict the commonly held belief that ENSO events only have short-term impacts on global temperature.

SOURCES

The NOAA Optimal Interpolated SST Analysis (OI.v2) Data is also available online through the NOAA National Operational Model Archive & Distribution System (NOMADS).
Overview:
http://www.emc.ncep.noaa.gov/research/cmb/sst_analysis/

THE ERSST.v2 data had to be accessed through the KNMI Climate Explorer website while NOMADS is being updated.
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere

The Sato Index Data is available from GISS at:
http://data.giss.nasa.gov/modelforce/strataer/
Specifically:
http://data.giss.nasa.gov/modelforce/strataer/tau_line.txt

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About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
This entry was posted in El Nino-La Nina Processes. Bookmark the permalink.

One Response to >There Are Also El Nino-Induced Step Changes In The North Atlantic

  1. Pingback: How Can Things So Obvious Be Overlooked By The Climate Science Community? | Bob Tisdale

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