The Barents Sea Hotspot Isn’t So Hot

I’ve moved to WordPress.  This post can now be found at The Barents Sea Hotspot Isn’t So Hot

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Blogger Richard 1 1 1 commented about the Barents Sea hotspot in the February 2009 NOAA/NESDIS SST anomaly map posted as part of the La Niña conditions: still there thread at WattsUpWithThat, Figure 1.

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Figure 1

As a second source of SST anomaly maps, I used the NOAA NOMADS system to create a February 2009 SST anomaly chart based on the OI.v2 SST data, Figure 2. Note that of the Barents Sea SST anomalies in the OI.v2 SST depiction are quite a bit lower than the NOAA/NESDIS version. The NOAA/NESDIS shows SST anomalies as high as 4.5 to 5 deg C, while the OI.v2 SST anomalies don’t rise above 2 deg C in the Barents Sea Hotspot area.
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Figure 2

THE DIFFERENCE BETWEEN THE TWO DATASETS

For those less technically inclined, the NESDIS and the OI.v2 SST datasets both use satellite data, but the OI.v2 data is adjusted based on buoy and ship readings.

For those looking for more technical information, here are the acronyms and the links. NOAA/NESDIS uses a Polar Operational Environmental Satellite (POES) with an Advanced Very High Resolution Radiometer (AVHRR) for SST anomaly data.

NOAA/NESDIS/OSPDP main page is here:
http://www.osdpd.noaa.gov/ml/index.html
Ocean datasets are here:
http://www.osdpd.noaa.gov/ml/ocean/index.html
The reference to the POES satellite for SST anomalies is here:
http://www.osdpd.noaa.gov/ml/ocean/sst.html
Sea Surface Temperature Chart selection page:
http://www.osdpd.noaa.gov/PSB/EPS/SST/climo.html
SST Methodology is discussed here:
http://coralreefwatch.noaa.gov/satellite/methodology/methodology.html#ssta
The POES satellite is discussed here:
http://www.oso.noaa.gov/poes/index.htm

For the OI.v2 SST data, NOAA/NCDC also uses Advanced Very High Resolution Radiometer (AVHRR) satellite technology for its SST data, but they supplement it with in situ readings from ships and buoys.

A full description of the OI.v2 data is discussed in the Reynolds et al (2002) paper “An Improved In Situ and Satellite SST Analysis for Climate”:
ftp://ftp.emc.ncep.noaa.gov/cmb/sst/papers/oiv2.pdf
And the reference to AVHRR satellite data is here:
ftp://ftp.ncdc.noaa.gov/pub/data/papers/200686ams8.1rrfree.pdf

A COMPARISON DURING A “COOL” MONTH

Figure 3 is a time-series graph of OI.v2 SST anomalies of the Barents Sea Hot Spot from November 1981 to February 2009. Note that there was a significant dip in SST anomalies during 2008. SST anomalies for the Barents Sea Hotspot reached their minimum level of -0.29 deg C in August 2008, in what appears to be a lagged response to the 2007/08 La Nina event.
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Figure 3

If we refer to the NOAA/NESDIS map for August 2008, Figure 4, the hot spot in the Barents Sea still exists.
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Figure 4

The map of the OI.v2 data, Figure 5, however, reflects the reduced SST anomaly in August 2008. It also shows lower SST anomalies than the NOAA/NESDIS map at all Northern Hemisphere high latitudes above approximately 65N.
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Figure 5

Note: Do not attempt to visually compare the two OI.v2 SST anomaly maps, Figures 2 and 5, without considering the difference in the color-coded temperature anomaly scale. The scale varies per month, and there’s no way to set it to one level in NOMADS.

INSTRUCTIONS FOR MAKING OI.v2 SST ANOMALY MAPS THROUGH NOMADS

The source of the OI.v2 SST anomaly maps is the NOAA NOMADS system. Refer to the following link.http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?lite
Under “Control File”, select “monoiv2.ctl…Monthly OIv2 SST” and under “Plot Type”, select “map”. Click on “Next Page”.
For “Field”, select “ssta *OIV2 SST monthly anomaly (C) rel to 1971-2000. Under “Time”, select the desired month and year. The “default” map projection is global, though a Robinson projection might be preferable to reduce the visual importance of the high latitudes. Click on “Plot” and a new window will appear with the map.

SUMMARY

The NOAA/NESDIS SST anomaly maps appear to have a bias at high latitudes and should probably be avoided for presentations of high-latitude SST anomalies for this reason. Based on the small sampling used in this post, the NOAA/NESDIS charts seem to register significantly higher SST anomalies at high-latitudes than the OI.v2 SST data, in which the satellite data is adjusted with in situ ship and buoy readings.