The 2007 Spike in Arctic Ocean SST

INTRODUCTION

The reasons for the drastic decline in Arctic Sea ice during 2007 include the reversal of Arctic Ocean currents, polar amplification exacerbated by of a string of El Nino events (2002/03, 2004/05, 2006/07) with no La Ninas to counteract them, the Arctic Oscillation, and others. Emphasizing the magnitude of that decline, the Arctic Ocean SST anomaly graph in my post Optimally Interpolated SST (OI.v2 SST) versus Extended Reconstructed SST (ERSST.v2) Data showed a significant spike in Arctic Ocean SST in 2007. To save you a click, the following is a graph of OI.v2 SST anomaly data for the Arctic Ocean [65N-90N] from November 1981 to October 2008. It clearly shows the anomalous 2007 rise in SST.

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Figure 1

The majority of the unusual sea ice loss in 2007 took place in and north of (moving west to east from Siberia to the Alaska-Canada border) the Laptev Sea, the East Siberian Sea, the Chukchi Sea, and the Beaufort Sea. Refer to the following video (MOV format, 5.66MB) of the 2007 Arctic melt season.
http://nsidc.org/news/press/2007_seaiceminimum/images/20071017_meltseasona.mov

SEGMENTING THE ARCTIC OCEAN SST ANOMALY DATA

Figures 2 and 3 illustrate how I divided the Arctic Ocean SST anomaly data into quadrants. The coordinates I used isolate most of the affected area.
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Figure 2
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Figure 3

Figure 4 shows the Arctic SST anomaly data (OI.v2 SST) from November 1981 to October 2008, with the data divided into the quadrants shown above. Sorry about the weight of the curves, but if they were heavier, the forward curves would hide those behind. The 2007 spike in SST anomaly took place in the area identified as “Siberia-Alaska”, the purple curve, confirming that the spike in SST simply reflects the unusual ice loss north of Eastern Russia and Alaska.
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Figure 4

But the 2008 Arctic sea ice loss was nearly the same as 2007, yet in 2008, Arctic SST in that area did not climb to the 2007 temperature. The sea ice loss in 2008 appears to have been more evenly distributed than it was in 2007. Refer to Figure 5, which are comparative sea ice maps near the peaks of the melt season, September 15, 2007 and 2008.
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Figure 5

SOURCES

Comparative sea ice maps are available from Cryosphere Today:
http://igloo.atmos.uiuc.edu/cgi-bin/test/print.sh

Optimally Interpolated Sea Surface Temperature Data (OI.v2 SST) is available through the NOAA National Operational Model Archive & Distribution System (NOMADS).
http://nomads.ncdc.noaa.gov/#climatencdc

Optimally Interpolated SST (OI.v2 SST) versus Extended Reconstructed SST (ERSST.v2) Data

INTRODUCTION

I would prefer to use ERSST.v3 in all posts since it’s the most up-to-date version of SST data, but I have yet to find a simple way to download time-series data for it. For short-term data, however, monthly Optimally Interpolated SST (OI.v2 SST) data is available from NOMADS from November 1981 to present. The OI.v2 SST data provides better resolution than ERSST.v2, but it’s obviously not a long-term data set. The improvements are discussed in the Reynolds et al paper (2002) “An Improved In Situ and Satellite SST Analysis for Climate”, Journal of Climate, 15, 1609-1625.
ftp://ftp.emc.ncep.noaa.gov/cmb/sst/papers/oiv2pap

This post provides a visual comparison of OI.v2 SST and ERSST.v2 SST data for the period that the two data sets overlap, November 1981 to present. As you will note, the OI.v2 SST data illustrates more detail for the Southern Hemisphere and the extreme high latitudes. For this reason, I’ve elected to use it as the source for future monthly SST updates.

THE DATA SETS WITH THE GREATEST DIFFERENCES

As noted above, the differences between OI.v2 and ERSST.v2 SST data for the Arctic and the Southern Ocean are significant. They are illustrated in the following two graphs. Note the spike in the 2007 Arctic Ocean SST anomalies. I’ll do a follow-up post on that blip to illustrate its primary location.
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Arctic Ocean SST Anomalies (65 to 90N)
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Southern Ocean SST Anomalies (60 to 90S)

NINO3.4 SST ANOMALY

There are no major differences between the two data sets for NINO3.4 SST anomalies.
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NINO3.4 SST Anomalies (5S to 5N, 170W to 120W)

HEMISPHERIC AND GLOBAL SST ANOMALIES

There is little difference between the two data sets for the Northern Hemisphere, but there are significant changes in the Southern Hemisphere data. These changes to the Southern Hemisphere are then reflected in the Global SST anomaly data.
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Northern Hemisphere SST Anomalies
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Southern Hemisphere SST Anomalies
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Global SST Anomalies

OCEAN SST ANOMALY DATA COMPARISONS

The following graphs compare SST anomalies for the Indian Ocean as a whole and for the North and South Atlantic and Pacific Oceans. As noted previously, the Southern Hemisphere data sets have the greater differences.
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North Atlantic SST Anomalies (0 to 75N, 78W to 10E)
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South Atlantic SST Anomalies (0 to 60S, 70W to 20E)
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North Pacific SST Anomalies (0 to 65N, 90 to 180W) & (0 to 65N, 100 to 180E)
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South Pacific SST Anomalies (0 to 60S, 70 to 180W) & (0 to 60S, 145 to 180E)
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Indian Ocean SST Anomalies (30N to 60S, 20 to 145E)
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SOURCE

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

Revised Ocean Heat Content

In my post The Ishii and Kimoto Proposed Update to Ocean Heat Content, I provided a link to the November 5, 2008, NASA Earth Observatory article “Correcting Ocean Cooling”. http://earthobservatory.nasa.gov/Features/OceanCooling/
Figure 1 is a copy of the graph of the Ocean Heat Content from page 4 of the article. It compares the original OHC data to the newly revised data. Unfortunately, they failed to document the depths for the data. If they did, I couldn’t find it in the article.

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Figure 1

Using the coordinate capabilities of MS Paint, I “duplicated” the graph in Figure 2 so that I could run a few quick comparisons.
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Figure 2

In Figure 3, the last few years of revised data have been deleted to make the time spans equal. Linear trends were then added. Note the minor decrease in trend between the original and the revised OHC data.
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Figure 3

Figure 4 is a comparative graph of OHC and the Multivariate ENSO Index (MEI). Regrettably, there was no simple way to scale the MEI data to make it easier to compare to OHC, so I simply left it as raw annual data. There does not appear to be a consistent reaction of OHC to ENSO events. Note how, counter-intuitively, the OHC rises and falls in synch with SST during the 1997/98 El Nino. One would expect the OHC to decrease during that El Nino since the tropical east Pacific discharged so much heat into the atmosphere, but the OHC rose. Then the variation in OHC opposes the La Nina that follows, as expected. That specific period was selected because it is not influenced by volcanic aerosols.
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Figure 4

The influence of stratospheric aerosols ejected from explosive volcanic eruptions can be seen in Figure 5. It‘s impossible, unfortunately, to draw any conclusions about the relationship between volcanic aerosols and OHC solely on this graph because volcanic aerosols are not the only significant natural variable capable of altering the amount of solar irradiance reaching the surface of the oceans.
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Figure 5

More unfortunate is the lack of long-term cloud cover data. The only cloud cover data sets I’ve found begin in 1980 or thereabouts. Refer to Figure 6, which shows a decrease (about 4 to 5%) in global Total Cloud Amount from 1986 to 2000, then an increase (about 2 to 3%) from 2000 to 2005.
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Figure 6

In Figure 7 I’ve compared OHC with annual scaled and ranged ERSST.v3 global SST data. Both display increasing trends, but the annual variability of SST far exceeds that of OHC.
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Figure 7

Figure 8 illustrates the annual change in OHC. The period of sustained volcanic aerosols from 1960 to the early 1970s clearly suppressed annual variations in OHC.
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Figure 8

CLOSING NOTE

At the end of my November 11, 2008 post about the Ishii and Kimoto proposed changes to OHC (linked above and below), I commented about the curious coincidence between the number of global ocean data profiles and the rise and fall in ocean heat content. It would be inappropriate for me to make the observation in that post but not in this, so I’ve repeated it here. While the revised OHC data in this post does not have the "hump" in the 1970s, OHC appears to have accelerated since the early 1990s. Oddly, this seems to coincide, though not perfectly in synch, with the surge in the number of readings.

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From The Ishii and Kimoto Proposed Update to Ocean Heat Content:

UPDATE (November 14, 2008): Please note that I am not implying any wrongdoing on the parts of those who calculate Ocean Heat Content. I simply found the following to be an odd coincidence, one that should be discussed.

The following is a graph of the number of global ocean data profiles accumulated monthly from 1979 to 2006 by the NCEP Global Ocean Data Assimilation System for a depth of 0-250 Meters from 90S to 90N. It’s odd that in recent years the Ocean Heat Content rises above its previous high in the 1970s, while at the same time the number of subsurface ocean temperature readings increases drastically. Then the Ocean Heat Content peak and decline about the same time as the number of readings.
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Number of Global Ocean Data Profiles

The Climate Prediction Center NCEP Global Ocean Data Assimilation System: Monthly Products webpage is here:
http://www.cpc.noaa.gov/products/GODAS/data_distribution.shtml

SOURCES

The Ocean Heat Content data was extracted from the graph in the above-linked NASA Earth Observatory article.

SATO Index data is available from GISS:
http://data.giss.nasa.gov/modelforce/strataer/tau_line.txt

Multivariate ENSO Index data is available from the NOAA Earth System Research Laboratory:
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/
Data:
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/table.html

Cloud Amount Graph is part of Figure 1 from Palle et al (2006)“Can Earth’s Albedo and Surface Temperatures Increase Together?” EOS Vol. 87, No. 4, 24 January 2006
http://www.iac.es/galeria/epalle/reprints/Palle_etal_EOS_2006.pdf