Rising sea levels causing longer days? – Watt?

“I couldn’t make this schist up even if I tried” by guest David Middleton

'Unprecedented' sea level rise is making Earth's days longer

Published July 15, 2024, 3:00 pm ET

go through Jesse Thomson

science reporter

The changing climate is affecting our planet in many ways—from powerful hurricanes and severe droughts to invasive species and ocean acidification—but there might be another strange effect you've never heard of.

Climate change may actually be slowly changing the length of the day on Earth, according to a new paper in the journal Proceedings of the National Academy of Sciences.

This is a result of rising sea levels caused by rising temperatures and melting polar ice caps, which results in a redistribution of mass from the Earth's poles toward the equator.

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Weekly newspaper

Weekly newspaper? Are they still open?

PNAS articles are paid for. However, the summary says it all…

Abstract

Melting of ice caps and global glaciers causes sea levels to rise, and mass transfer from the poles to the equator increases the oblateness of the Earth, resulting in an increase in the length of day (LOD). Here we use observations and reconstructions of Earth surface mass changes since 1900 to show that the climate-induced LOD trend hovered between 0.3 and 1.0 ms/cy during the 20th century but accelerated to 1.33 ± 0.03 ms/cy since 2000. cy We further show that surface mass transport fully explains the accelerated trend in Earth's oblateness observed over the past three decades. We derive an independent measurement of the decreasing trend in LOD due to glacial isostatic adjustment (GIA) of −0.80 ± 0.10 ms/cy, which provides a constraint on mantle viscosity. The sum of GIA rates and lunar tidal friction fully explains the long-term LOD trends inferred from eclipse records three millennia before contemporary climate change. Projections of future climate warming under high-emission scenarios indicate that the climate-induced LOD rate may reach 2.62 ± 0.79 ms/cy by 2100, exceeding lunar tidal friction and becoming the most important factor in long-term LOD changes.

Proceedings of the National Academy of Sciences

Models all the way down. Changes in length of day (LOD) in milliseconds per century (ms/cy) cannot be measured over any time period, let alone on centennial to decadal scales. Why not try to determine “How many angels can dance on the head of a pin?”

LOD generally increases over geological time (Mitchell & Kirscher, 2023 ). As the Earth pushes the Moon farther away, the Earth's rotation slows down.

1.33 milliseconds/cycle = 0.0000133 seconds/year

At a rate of 0.0000133 seconds per year, in 80 million years the sidereal day will be 18 minutes longer than it is now.

Back in the Cretaceous (~80 mya), when sea levels were much higher than today and there was little to no polar ice, the length of the day was about 23.5 h (de Winter et al., 2020). The LOD change rate from 80 mya to the present (1950 AD) is approximately 2.25 ms/cy.

Keep this in mind: from 80 mya to 1950 AD, the LOD rate of change was approximately +2.25 ms/cy. Since AD ​​2000, the rate of LOD change said to be driven by “unprecedented” sea level rise is only +1.33 ms/cy.

Of course, there are no LOD measurements for the Cretaceous. This is a reconstruction based on the bold shell and model…the error bars are in days and hours…not milliseconds.

Measurement level of detail

The current LOD can be measured directly with great accuracy. Schreiber et al., in 2023, used a “laser ring gyroscope” to measure changes in the sidereal day. They found that the LOD fluctuated by as much as 6 milliseconds over the 120-day measurement period.

If the LOD fluctuates by 6 milliseconds over two months, then the correlation of an increase in LOD of 1.33 ± 0.03 milliseconds per century is equivalent to the correlation of a sea level rise rate of 1-3 mm per year with a daily tidal range of 1 meter.

refer to

de Winter, NJ, Goderis, S., Van Malderen, SJM, Sinnesael, M., Vansteenberge, S., Snoeck, C., Belza, J., Vanhaecke, F. and Claeys, P. (2020), Subdaily- Vanhaecke, F. and Claeys, P. (2020), Subdaily-scale chemical changes Torreto to Sanchez Thick-shelled shells: Implications for thick-shelled paleontology and the Cretaceous diurnal cycle. Paleooceanography and Paleoclimatology, 35:e2019PA003723. https://doi.org/10.1029/2019PA003723

Mitchell, RN, Kirscher, U. Nat. Geography. 16, 567–569 (2023). https://doi.org/10.1038/s41561-023-01202-6

Schreiber, K.U., Kodet, J., Hugentobler, U. et al. Measure changes in the Earth's rotation rate using a ring laser interferometer. Nat. Photons. number 17, 1054–1058 (2023). https://doi.org/10.1038/s41566-023-01286-x

Shahvandi MK, Adhikari S, Dumberry M, Mishra S, Soja B. Proceedings of the National Academy of Sciences USA A. 2024 Jul 23;121(30):e2406930121. DOI: 10.1073/pnas.2406930121. Epub July 15, 2024.

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