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From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: OT. Days getting longer.. ???
Date: Tue, 16 Jul 2024 19:46:41 +0200
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On 7/16/24 18:22, Martin Brown wrote:
> On 16/07/2024 15:18, Jeroen Belleman wrote:
>> On 7/16/24 13:01, jim whitby wrote:
>>>
>>> Rising sea levels caused by climate change are making the Earth "fatter"
>>> at the equator - slowing down its rotation and making the days longer.
> 
> It is pretty much uniformly distributed over the Earth's surface.
> 
>>> <https://e3.365dm.com/23/02/1920x1080/skynews-planet-earth-
>>> sun_6072574.jpg?20230228074839>
>>
>> Oh swell! So we can measure the rise in sea level by measuring
>> the length of the day. Data, anyone?
> 
> It is real - inferred from VLBI data. It is sensitive enough to detect 
> seasonal variations in the northern hemisphere summer (and has been for 
> quite a while). The asymmetry of land masses north and south of the 
> equator. When trees are in leaf in US Canada Russia forests the Earth's 
> moment of inertia is increased by the weight of sap and leaves.
> 
> https://www.researchgate.net/publication/261039439_On_the_length_of_day_with_2008-2010_VLBI_observations
> 
> Fairly recent example of such data above. This is the current global 
> solution from the Paris Observatory (seasonally detrended).
> 
> https://ivsopar.obspm.fr/24h/index.html
> 
> Most of the slowdown comes from tidal drag from sun and moon. Some 
> changes are a result of oceanic currents shifting around too.
> 
> Effects of glaciers melting can go either way depending on what altitude 
> the ice in the glacier was at (many glaciers are at high altitudes).
> 

Thank you for these references. Interesting. I was momentarily confused
by some of the French site's polar motion graphs labelled in 'as'. I
gather those are arcseconds, not attoseconds. ;-)

I see that LOD is far more involved than the OP implied. Getting an
undisputable sea level signal from LOD data is not going to be clear
cut.

Everyone appears to be worrying about phenomena deeply buried in
noise these days,

Jeroen Belleman