Polar motion special update | is something pulling us toward 30 E?

[00:00:00]So, I wanted to give a update on polar motion because, you know, last week I plotted a couple charts. One was this plot that looks at polar motion over the past 50 years, and there's this, you know, fairly distinct turn around the year 2000 where things go from drifting more or less towards 78 West, and they kind of take a little bit of a track which is, you know, closer to the prime meridian.

[00:00:31]Now, the generally accepted reason why things drift towards 78 West is that Greenland's been melting. That's been displacing where the kind of net center of of gravity is, and it makes sense to me. I mean, it's in the right part of the world. It's at the right meridian to do that. So, then the question becomes, well, what changed in 2000? Well, I I don't think Greenland suddenly stopped melting, but if you do the sort of just quick and dirty visual vector subtraction, if you will, it looks as if a second vector of motion was overlaid in addition to Greenland melting. And that second vector would be something kind of roughly towards 30 East. Um, and for those of you who are familiar with ECDO theory, that meridian is conspicuous because that's where I believe at one point over the past several thousand years the pole actually was there.

[00:01:37]That's the kind of, you know, 50-year trend.

[00:01:40]On a much, much shorter time scale, over the past couple months, there have been these few little kind of curious uh speed ups where over the past couple months, uh like every 10 or 11 days or so, the velocity takes a little bit of an uptick. You can kind of see in this chart here where it goes from being blue to being green. And those those upticks are all pointed more or less towards 30 East and you know all have a pretty visible increase in the velocity.

[00:02:16]What does this mean? Well, if you are of a particularly anxious and and paranoid type, then the question that might cross your head is do we have a sudden acceleration of our net motion towards 30 East? Is something about that Meridian pulling us towards it faster now than it has been over the past you know few decades?

[00:02:42]So, how can we interrogate this to see if this is actually something to be concerned about?

[00:02:49]There is a known atmospheric phenomenon where the atmosphere can with a certain periodicity, which is near 10 days, give a very very gentle tug upon the Earth.

[00:03:03]And this is a essentially a a Rossby wave as discovered by the Swedish-American meteorologist Carl-Gustaf Rossby.

[00:03:12]More good news. This data is published on an almost hourly resolution by the Geoforschungszentrum in Germany. Don't worry, all that means is the German Research Center for Geosciences.

[00:03:26]The Geoforschungszentrum has put together this snappy webpage here where you can see and download some of their latest data on these contributions. The two key folders you want to look at here are the operational AAM and operational OAM. AAM is atmospheric angular momentum. OAM, as you you guess, is oceanic angular momentum.

[00:03:53]Now, I will confess that I was a bit lazy and I just used Claude to kind of ingest the data here and do the do the the quick math on what the anticipated contributions toward polar motion would be.

[00:04:10]And the encouraging thing here is that the timing of when you saw a when you see a spike in the atmospheric angular momentum, the timing of when you see a spike lines up with when we see these these spikes here.

[00:04:28]The direction lines up and the relative magnitude lines up. So here for um for four select dates here, the predicted direction where the which is the direction that we anticipate the pole to move based on the contribution from the atmospheric angular momentum is listed here and you know, they're typically within 10 20 degrees. That's that's pretty good. Um the timing, the fact that each of these little spikes happens at right about the same time we see the polar motion move, that means you're probably onto something. And the the last point here is on magnitude. In rough numbers, the the math says that the angular momentum from the atmosphere and ocean should be moving the pole by about maybe 1 to 2 milliarc seconds. And I mean, if you look at the speed up that we actually saw from 1 to 1 and 1/2, that's pretty close.

[00:05:30]So the the good news here is that we have a very pedestrian unscary explanation for data that might have looked a bit scary at first. And I think being able to kind of take that step back and say, "Hey, the the sky is not falling."

[00:05:48]It is maybe a point of counterbalance that is at times scarce within within this community.

[00:05:55]For those of you who want to go and kind of repeat this analysis at home, we've got the Python file here that got spat out by by Claude. Happy to to give that to you if it's useful. And this is I think a practice that if we see other odd-looking polar motion anomalies over the next, you know, months that come, this will be a good check to go and make sure that we don't have to invoke any exotic explanations for behavior which might be a lot more pedestrian.