The Climate Letter for September 28 contains an image showing a quite warm temperature anomaly covering muvh of the Arctic Ocean. The story told how the anomaly seemed not to be affected by the amount of sea ice on the surface, which was split about 50/50, nor was it detained by heavy cloud cover over almost the entire ocean. Nothing was said about water vapor coverage at the time. I have noticed that a very similar anomaly has appeared in roughly the same place every single day since then, including today—image below. One difference now is that the anomaly is stronger than before, up to about +12C in the center. Cloud cover and sea ice conditions are nearly the same as before, but sea ice presence may now be having a more active effect on temperature distribution. What I want to investigate today will focus on water vapor effects.
The next image shows two separate intrusions of water vapor moving into the ocean zone, one coming from the Bering Strait area and the other from the European side. The one from Bering Strait is less massive as it approaches the zone but more effective in penetration, digging in deeper with somewhat higher weight readings, producing the strongest part of the temperature anomaly. The European vapor mass, after exploiting its broad warming effect over a vast area extending far to the south, can be seen running into kind of a brick wall that clearly diminished its power at this point:
Let’s have a look at the source of that brick wall, by going to the Jetstream map. Along with a big jet, Greenland’s elevation stands out as half the story, just as it usually does, in common with other regions of high elevation. Notice how the Bering Strait intrusion also had a bit of jet wind to deal with, but much smaller and weaker than the other:
This is a good occasion for showing actual temperatures that come into play while establishing the Arctic anomalies. Begin with the light green +1C on the top side of the ocean, then a layer that turns into -5C, just below it, another at -10C below that, and finally -15C in the layer just above Greenland, which is where the warm anomaly has changed to cold. At the last minute I have noticed that there was a break in the cloud cover exactly where the warmest anomaly patch lies, so maybe it allowed in enough sunshine to make a difference of one or two degrees in that spot?
The real story here is that a relatively small weight of water vapor intrusion—which arrived at jetstream altitude—was enough to produce major temperature anomalies in the Arctic yesterday, and probably over no fewer than a dozen previous days in much the same way. In yesterday’s letter we saw that creators of 25 of the world’s most advanced climate forecasting models have no real interest in basing future predictions of polar temperatures on water vapor activity of this type. How many days like this will it take to get them interested?
Carl