Climate change and polar ice melting could be impacting the length of Earth's day

[Admin]

Humanity's activities and climate change are impacting the polar ice sheets, causing excessive melting, and this is slowing Earth's rotation, challenging official timekeeping standards.

Climate change and polar ice melting could be impacting the length of Earth's day : Read more

 

[Helio]

It would be interesting to see the data on Earth's rotation rate. There is a group that uses quasar positions to find millisecond variations in our rotation rate. Air mass movements are the main source of variations, IIRC. I recall the change in our rotation rate when the large tsunami (Indonesia) hit, though it was not the largest cause for that time period.

I would assume the ice melts would demonstrate a net increase in our rotation period, but perhaps not much.

 

[Ken Fabian]

I would assume the ice melts would demonstrate a net increase in our rotation period, but perhaps not much.

Ice melt will move mass from nearer the poles to nearer the equator; I would expect that to slow Earth's rotation. Observation (and theory) shows that ice sheet mass loss causes sea levels nearby to fall due to local gravity effects; it is furthest away from them that gets the most sea level rise.

I expect that keeping the clocks in sync with Earth's rotation will be the least of the issues from global ice loss - which is already up to 60 metric tons of ice sheet melt per person per year. And the impacts of ice loss may be huge in the longer term but other climate impacts will be more near term.

 

[Helio]

Ice melt will move mass from nearer the poles to nearer the equator; I would expect that to slow Earth's rotation. Observation (and theory) shows that ice sheet mass loss causes sea levels nearby to fall due to local gravity effects; it is furthest away from them that gets the most sea level rise.

I expect that keeping the clocks in sync with Earth's rotation will be the least of the issues from global ice loss - which is already up to 60 metric tons of ice sheet melt per person per year. And the impacts of ice loss may be huge in the longer term but other climate impacts will be more near term.

Yes. There are areas where the reduction of ice mass due to melting causes a rise in the land, which distorts the real sea level rise estimates.

My thought is that the millisecond measurements in the Earth’s reduction in the average rotation rate might be a useful, and more accurate, way to measure real sea level rise.

However, the rise in the land would likely make this too complicated.

 

[billslugg]

"ice sheet mass loss causes sea levels nearby to fall due to local gravity effects"

This statement does not refer to isostatic rebound from ice sheet loss, but the gravitational attraction of the ice sheet, pulling the nearby waters towards it. This is why Greenland's seal level will drop as the ice sheet is lost. Isostatic rebound will also play a role. However, isostatic rebound occurs upward only where the ice sheet was thick. Near the coast, that area goes downward to compensate. This is why US East Coast isostatic rebound of the land is downward. Canada is moving upward, US East coast downward.

 

[Unclear Engineer]

This whole subject of ice sheet effects on Earth's rotation is something that I have been asking about for over 2 decades, but mostly my questions have been ignored.

The current article about ice loss affecting day length is trivial compared to what must have happened when the 2-mile-thick ice sheets in the northern hemisphere melted rather rapidly about 20,000 years ago, raising sea level by around 325'. The Earth is still a little "pear shaped" as the rock slowly adjusts to having been depressed under the continents in the northern hemisphere, and some land is still rebounding upward, while the areas that were not glaciated are still slowly sinking back down.

So, what is happening now is only "unprecedented" in that humans are measuring and recording it. Much larger effects have already happened in human experience.

But, not only should the interglacial period melting have affected the day length by a lot more than what his article is talking about, I am thinking that it should have also affected the rate of "wobble" of our spin axis, just like pressing on a spinning top makes it wobble differently. Wouldn't that have changed the rate of precession and made different frequencies of the Milankovitch cycles? Could taking that into account help make the global climate models better match the geological records for the actual ice age frequencies?

 

[Classical Motion]

Our problem with earth time is not the rate of rotation. Any rate will cause the same problem. Because it takes more than one, 360 degree rotation to line up with the sun every day. Earth's rotation is not absolute, it's relative to our star. Not still space. A result of motion mechanics.

You may use math to describe and measure it, but not power or reason it. Math has no power or reason. Math is NOT self powered. Like mass is.

 

[Unclear Engineer]

Earth's rotation can be measured against "fixed" stars - stars that do not appear to move from Earth's perspective - at least not in an amount that matters to determining a fixed direction. So, one 360 degree rotation is called a "sidereal day", and it is shorter than a "solar day" because the Earth needs to rotate (on average) 360 + 360/365.25 degrees to get the same point directly facing the Sun the next day. Of course, there is some variability of that solar day length because the Earth's orbit is elliptical, not perfectly circular, and its angular progress around the Sun varies in speed.

What this article is talking about is the rotation rate of the Earth as measured against the "fixed" stars, which can be determined quite precisely.

And, that varies some, too, for a variety of reasons both short term and long term.

 

[Helio]

Earth's rotation can be measured against "fixed" stars -

There is a group, which a quick search didn't find, that uses quasars since their great distance gives greater accuracy.

There is also the G. This is a new underground laser system that measures hourly, apparently. [Not sure if it's fully operational yet.]

 

[Ken Fabian]

Yes. There are areas where the reduction of ice mass due to melting causes a rise in the land, which distorts the real sea level rise estimates.

That was not what I was pointing out - the sea level fall around where ice mass is lost is due to reduced local gravity from the reduced mass. It is a rapid response to change in local gravity. Isostatic rebound - land rising - from less mass is a lot slower and is a different phenomena.

 

[Helio]

That was not what I was pointing out - the sea level fall around where ice mass is lost is due to reduced local gravity from the reduced mass. It is a rapid response to change in local gravity. Isostatic rebound - land rising - from less mass is a lot slower and is a different phenomena.

It seems likely that the rebound would be slow in accord with slow melting. If a vast, mile-thickness glacier, however, were to vanish instantly, I would expect a very quick rebound.

 

[Atlan0001]

Fresh water diluting the salts of the seas cause changes in flow patterns. Changes in flow patterns cause changes in tidal patterns. Changes in tidal patterns cause changes in Earth's rotational patterns. The Earth may rebound, once more, when the sudden collapse into a lengthy 'Ice Age' has run Ice Age's course and turned around into an interlude of warming once more . . . if it follows the pattern of past 'ages'.