SST Anomalies By Global Quadrants

INTRODUCTION

Normally, I’ve been segmenting data according to ocean and hemisphere or some portion thereof. I needed a break from the series I’ve been doing on the tropics, so I decided to divide the Globe into quadrants, Figure 1, and see what oddities came to light when I plotted the SST anomalies for the four areas.

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Figure 1

As you’ll note, the simplistic approach did a reasonable job of isolating ocean data sets. There’s some overlap--Pacific with Atlantic, Atlantic with Indian, etc.--but it’s a starting point to see if there would any reason to carry an investigation further. The quadrants also include their respective portions of the Arctic and Southern Oceans, so they’re not solely those major oceans. The findings do justify that I put time into creating full ocean data sets and present them in a future post.

Note: All graphs in this post are of monthly long-term data sets, 1854 to 2008. The comparison graphs have been smoothed with 37-month filters, while the graphs of single data sets use 12-month filters. The NINO3.4 data in Figure 3 has not been smoothed.

SST ANOMALIES BY GLOBAL QUADRANTS

Figure 2 shows the SST anomalies for four segments of the globe:
- Far West - 90 to 180W (Purple)
- Near West – 0 to 90W (Red)
- Near East – 0 to 90E (Green)
- Far East – 90-180E (Blue)

The big eye catcher is the 6- to 7-year lag of the Far West SST anomalies during the late 1800s/early 1900s drop in SST. The Eastern Pacific makes up the majority of this area.
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Figure 2

There were 4 moderate El Nino events in 1896/97, 1899/1900, 1902/03, and 1904/05, Figure 3, with only 2 mild, slightly counteracting La Ninas in 1898/99 and 1903/04.
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Figure 3

The relative strengths of those El Ninos versus the La Ninas at that time are better illustrated by the NINO3.4 data that’s been smoothed with a 37-month filter. Refer to Figure 4. Could these El Ninos have delivered sufficient heat to the East Pacific to keep its SSTs from dropping at the same time as the other data sets?
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Figure 4

Figures 5 through 8 are graphs of the individual data sets for the four quadrants smoothed with 12-month filters. They’re being provided as reference. All four quadrants display the typical drop in SST anomaly from the late 1800s to the early 1900s. SSTs rise to the 1940s in the Near West, Figure 6, and Near East, Figure 7, quadrants, then decrease to the mid-1960s, when then they rise again. The spike around 1940 in the Near East data (Figure 7) is an extreme example of the abnormal rise in SST anomaly in the Indian Ocean and in parts of the Southern Hemisphere. Illustrating good portions of both hemispheres of the Pacific Ocean, the Far West, Figure 5, and Far East, Figure 8, data sets rise more gradually from 1910s to present, with a comparatively minimal rise in the 1940s.
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Figure 5

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Figure 6

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Figure 7

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Figure 8

COMPARATIVE GRAPHS

Figure 9 illustrates the SST anomalies for the Far East and Far West quadrants. The delayed decrease in the Far West SST anomaly around 1900 is very clear in this illustration. The two data sets, while they do share common overall trends, appear at times to be out of synch, as if heat is shifting back and forth across the Pacific. Which it does.

During El Nino events, the Pacific Warm Pool (contained within the Far East data set) delivers heat to the NINO3.4 area (part of the Far West data set), where it is upwelled. Through oceanic Rossby waves, the warm surface water is sent east, where it rebounds off the Central and South American Coasts. The oceanic Rossby waves then travel North and South along the coasts and westerly in multiple directions. In addition, clockwise ocean currents in the North Pacific and counterclockwise ocean currents in the South Pacific return the heat to the West Pacific (Far East data set). Refer to the following video from NASA, especially the 97/98 El Nino that starts in January 1997 with the first of two Kelvin waves travelling west to east. Note: It’s a large video, 17mb.
http://topex-www.jpl.nasa.gov/gallery/tiffs/videos/tpglobal.mpeg
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Figure 9

Figure 10 illustrates the SST anomalies for the Near East (primarily the Indian Ocean) and the Near West (primarily the Atlantic). While they follow the same overall trends, there are substantial periodic differences that do not appear to be caused by ENSO.
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Figure 10

Subtracting the Near East (Indian) from the Near West (Atlantic), creates a curve, Figure 11, that bears what appears, at first, to be a function of the Atlantic Multidecadal Oscillation (AMO).
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Figure 11

But when the curve created by subtracting the Near East from the Near West data set is compared to the AMO, the differences become obvious. See Figure 12.
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Figure 12

A comparative graph of the North Pacific Residual and “Near West Minus Near East” data shows a better correlation, but it’s not perfect. Also, it would be tough to explain.
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Figure 13

What’s that cycle induced by? Maybe that will become obvious when I divide Global SST into ocean data sets, including both hemispheres.

SOURCE

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

Tropical SST Anomalies Revisited – East Pacific Ocean

PREVIOUS POSTS IN SERIES

Tropical SST Anomalies Revisited – Introduction
http://bobtisdale.blogspot.com/2008/09/tropical-sst-anomalies-revisited.html

Tropical SST Anomalies Revisited – Atlantic Ocean
http://bobtisdale.blogspot.com/2008/09/tropical-sst-anomalies-revisited_24.html

AREAS INCLUDED

Figure 1 illustrates the geographic areas included in this post and their coordinates. They include the:
-Tropical Northeast Pacific (0-20N, 90-180W)
-Tropical Southeast Pacific (0-20S, 70-180W)
-Northeast Pacific (0-65N, 90-180W)
-Southeast Pacific (0-60S, 70-180W)
-Northeast Pacific Upwelling Area (32-48N, 116-132W)
-Southeast Pacific Upwelling Area (16-48S, 70-78W)
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Figure 1

NORTHERN AND SOUTHERN TROPICAL EAST PACIFIC

The long-term (January 1854 to August 2008) SST Anomalies for the Northern and Southern Tropical East Pacific are shown in Figure 2. The data has been smoothed with an 85-month running average filter. Note how the sign of the difference between the two data sets shifts with time. Before the 1920s and after 1976, the Southern Tropical East Pacific anomalies are higher in temperature than the Northern Tropical East Pacific, and between the 1920s and 1976, the Southern Tropical East Pacific anomalies are lower in temperature than the Northern Tropical East Pacific.
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Figure 2

In Figure 3, I’ve subtracted the Southern Tropical East Pacific anomalies from the Northern Tropical East Pacific anomalies. I’ll have to examine oceanic SST dipoles in a future post.
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Figure 3

Figure 4 (raw data) shows the short-term (January 1978 to August 2008) SST Anomalies for the Northern and Southern Tropical East Pacific. The Southern Tropical East Pacific shows the greater variation.
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Figure 4

OFF TOPIC – THE GREAT PACIFIC CLIMATE SHIFT OF 1976

Refer back to Figure 2. Note the sharp rise in SST anomalies at 1976 in both Northern and Southern Tropical East Pacific data sets. Is that an indicator of the Great Pacific Climate Shift of 1976? Normally, that shift is discussed in terms of changes in the Pacific Decadal Oscillation and in El Nino frequency. There are a few papers, however, that discuss the actual shift in basin-wide Pacific SST. In Figure 5, I’ve provided a short-term graph of the Northern and Southern Tropical East Pacific SST anomalies from January 1960 to December 1985. Note how the trends before and after 1976 are different.
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Figure 5

To help illustrate the change in trend and the jump in SST, I’ve shown only the Southern Tropical East Pacific SST anomalies and added linear trend lines for two periods, from January 1960 to December 1975 and from January 1977 to December 1955, in Figure 6. Based solely on the end and start points of the two trend lines, the Southern Tropical East Pacific SST anomalies stepped up almost 0.5 deg C during 1976. When I’m finished with this series, I will examine the Pacific Ocean on a basin wide basis to determine the total impact of the Great Pacific Climate Shift.
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Figure 6

IS THE SOUTHERN OCEAN INFLUENCIAL?

In Figure 7, I’ve compared Southern Ocean SST anomaly data to Northern and Southern Tropical East Pacific SST anomalies. There appears to be little relationship between the Southern Ocean and the Tropical Pacific.
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Figure 7

However, Smith and Reynolds provided a much updated representation of the Southern Ocean in their latest version of SST data, ERSST.v3. In Figure 8, I’ve replaced the ERSST.v2 data for the Southern Ocean with the ERSST.v3 data. The Southern Ocean definitely influences the Eastern Tropical Pacific Ocean.
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Figure 8

Subtracting the Southern Ocean SST anomalies from the Northern and Southern Tropical East Pacific SST anomalies creates two curves with an apparent long-term oscillation. Refer to Figure 9. I found the overall shape of the curve in Figure 9 and the points at which the trends changed interesting. (Note that the ERSST.v3 data is only available, in simple format, in specific latitude bands and only from January 1880 to April 2008. They stopped updating it in April. For this reason, the span of the graph has been reduced.) Don’t concern yourself with the spikes at 1994, three years before the 97/98 El Nino. It’s simply a product of the smoothing.
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Figure 9

If the smoothing is changed from 85 months to 12 months, Figure 10, the El Ninos and La Ninas appear at the correct times for the most part.
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Figure 10

In Figure 11, I’ve returned to a straight comparison of monthly data for the Southern Ocean and the Northern and Southern Tropical East Pacific SST anomalies for the years 1965 to 1985. The data is raw. The Southern Ocean data appears not to be the cause of the 1976 climate shift.
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Figure 11


COMPARISON TO NINO3.4

As one would expect, SSTs in the NINO3.4 area are a major influence on the SSTs of the Tropical East Pacific. Refer to Figure 12. But there are differences in the underlying trends. These differences would be caused by the additional influences of the North and South Pacific.
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Figure 12

The magnitudes of the variations caused by ENSO make a simple cause and effect evaluation difficult, which will be seen in the following, much more difficult than that of the Tropical Atlantic in the prior post.

NORTHERN TROPICAL EAST PACIFIC

Figure 13 illustrates SST anomalies for the Northeast Pacific and for the Northern Tropical East Pacific. The overall changes in trend agree with one another. There are differences in the overall amplitude of the decadal variations, which may be due to the additional thermohaline circulation/meridional overturning circulation component in the North Pacific, or due to the reductions in the effects of NINO3.4 as the perturbations are spread out over a large area, or a combination of both.
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Figure 13

Figure 14 compares the SST anomalies of the North East Pacific Upwelling area and for the Northern Tropical East Pacific.

Ocean currents do run from North to South along the North American coast, so the Upwelling area waters do feed the tropics. But ENSO events also distribute changes Northward through Rossby waves. These ENSO fed variations should then be returned over time to the tropics, creating a delayed feedback to the tropics. The North East Pacific Upwelling area is also smaller in area than the Northern Tropical East Pacific so it should reflect the variations more.
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Figure 14

Note: I could but will not attempt to extract the base NINO3.4 component from the other signals. Maybe a future post.

SOUTHERN TROPICAL EAST PACIFIC

The SST anomalies for the Southeast Pacific and for the Southern Tropical East Pacific are compared in Figure 15. Like their Northern counterparts, there are differences between the two. However, the Southern Ocean would also have an influence on these data sets.
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Figure 15


The Southern Tropical East Pacific and the coastal upwelling area off the Southwest coast of South America are compared in Figure 16. Again, like the Northern Tropics and Upwelling area, the influences of ENSO on both these data sets, along with the feedbacks due to ocean currents, would make it difficult to isolate the variables using simple tools.
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Figure 16

CLOSING COMMENTS

While I had expected to find a clearer relationship between the North and South American west coast upwelling areas and the Tropical East Pacific, I was not disappointed with this post. The relationship between the Southern Ocean (ERSST.v3) and the Tropical East Pacific (Figure 8) was revealing, especially when the negative trend in the Southern Ocean SST over the last 20+ years is considered. Will the Tropics follow? The other find I was pleased with was the 1976 SST shift that’s easily visible in the North and South Tropical East Pacific data. Refer again to Figures 2, 5, and 6.

SOURCES

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

The more recent version of the Smith and Reynolds Extended Reconstructed SST (ERSST.v3), along with land surface temperature and combined (land + ocean) surface temperatures, are available in various latitudinal bands at:
ftp://eclipse.ncdc.noaa.gov/pub/ersst/pdo
Don’t let the PDO in the address confuse you. There’s much more there. The overview for the update is here:
http://www.ncdc.noaa.gov/oa/climate/research/sst/ersstv3.php

Tropical SST Anomalies Revisited – Atlantic Ocean

PREVIOUS POST

Tropical SST Anomalies Revisited – Introduction
http://bobtisdale.blogspot.com/2008/09/tropical-sst-anomalies-revisited.html

AREAS INCLUDED

Figure 1 illustrates the geographic areas included in this post and their coordinates. They include the:
- Tropical North Atlantic (0-20N, 78W-10E)
- Tropical South Atlantic (0-20S, 50W-15E)
- North Atlantic (0-70N, 70W-10E)
- South Atlantic (0-60S, 70W-20E)
- North Atlantic Upwelling Area (12-28N, 14-24W)
- South Atlantic Upwelling Area (12-30S, 4-14E)

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Figure 1

NORTHERN AND SOUTHERN TROPICAL ATLANTIC

The long-term (January 1854 to August 2008) SST Anomalies for the Northern and Southern Tropical Atlantic are shown in Figure 2. The data has been smoothed with an 85-month running average filter. The Southern Tropical Atlantic has the greater swing in SST over the term of the data, with much of that variation caused by a significant drop in SST from the late 1890s to 1906 and the rebound from 1906 to the mid-1920s.
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Figure 2

Figure 3 (raw data) shows the short-term (January 1978 to August 2008) SST Anomalies for the Northern and Southern Tropical Atlantic. Again, the Southern Tropical Atlantic shows the greater variation. I found two differences between the two data sets interesting. In 1984, the Southern Tropical Atlantic almost appears to be reacting to an El Nino when none took place that year; to the contrary, 84/85 included a La Nina. Also, there was a dip in Southern Tropical Atlantic SST early in 1997, before the 97/98 El Nino.
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Figure 3

Smoothing the short-term data with a 12-month filter, Figure 4, helps illustrate two things. That early 1997 dip in temperature appears it might lose its novelty and looks like it might have been part of a possible periodic oscillation. The second noticeable effect revealed by the smoothed data is the shift (rise) in the Southern Tropical Atlantic SST trend after the 97/98 El Nino.
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Figure 4

NORTHERN TROPICAL ATLANTIC

Figure 5 is a comparative graph of SST anomalies for the North Atlantic and for the Northern Tropical Atlantic. While the overall changes in trend agree with one another, it is clear that the one of the two data sets had an additional driver prior to the mid-1960s. They agree remarkably well afterwards. I have no explanation.
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Figure 5

Figure 6 is the short-term data for the North Atlantic and for the Northern Tropical Atlantic. In recent years the two data sets coincide well. The Tropical data has the greater variation, which is expected for an oceanic data set with a smaller area.
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Figure 6

In Figure 7, the Northern Tropical Atlantic data is compared to the coastal upwelling area off the Northwest coast of Africa. Those two data sets agree over the term of the data, with the upwelling area having exaggerated swings in SST. Since the Canary Current is from North to South along the West coast of Africa, the North Atlantic Upwelling area appears to drive the temperature of the Tropical North Atlantic. It must be recalled however that SSTs of those areas “upstream” of the upwelling area also impact the Tropical North Atlantic, as do the surface waters passing from the South Atlantic to the North Atlantic as part of the overall thermohaline circulation circuit.
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Figure 7

The short-term comparison of SST anomalies for the Northern Tropical Atlantic and the North Atlantic Upwelling area is illustrated in Figure 8. Again, the signals in the smaller geographic region are not dampened by area, so the variations in the Upwelling area are greater. Note that the anomaly (spike) at 2002 is greater than the value at 1998 even though the 2002/2003 El Nino was significantly smaller than the 97/98 El Nino. Interesting.
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Figure 8

SOUTHERN TROPICAL ATLANTIC

The SST anomalies for the South Atlantic and for the Southern Tropical Atlantic are compared in Figure 9. There are enough differences between the two data sets to suggest that the South Atlantic does not drive the Southern Tropical Atlantic.
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Figure 9


The Southern Tropical Atlantic and the coastal upwelling area off the Southwest coast of Africa are compared in Figure 10. Those two data sets agree over the term of the data, with the upwelling area having exaggerated swings in SST. The Benguela Current would carry the waters from the upwelling area northward along the Southwest coast of Africa to the Tropical Southern Atlantic. The South Atlantic Upwelling area appears to drive the temperature of the Tropical South Atlantic. Again, it must be remembered that SSTs of those areas “upstream” of the upwelling area also impact the Tropical South Atlantic.
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Figure 10

Figure 11 illustrates the short-term SST anomalies for the Southern Tropical Atlantic and the South Atlantic Upwelling area. Again, the signals in the smaller geographic region have greater variations. But note that the significant drop in SST immediately before the 1997/98 El Nino also appears in the upwelling data. As opposed to being a part of a possible oscillation as noted in the discussion of Figure 4, this time the plunge in SST appears anomalous. I’ll have to keep an eye out for that in other upwelling areas.
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Figure 11

For information purposes only, the last graph, Figure 12, provides a comparison of the SST anomalies for the upwelling areas for the North and South Atlantic.
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Figure 12

SOURCE

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