A Return to Phanerozoic Average Sea Level?

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Discussion Overview

The discussion revolves around the potential for a return to average sea levels characteristic of the Phanerozoic era, exploring geological and climatic implications over millions of years. Participants speculate on the cyclical nature of sea level changes, the impact of ice sheets, and the future geological record of humanity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest we might be nearing the end of a large cyclical regression similar to the Permian end regression, questioning if a natural trend could lead to a significant rise in sea level independent of human influence.
  • Others express skepticism about the speculative nature of long-term predictions regarding sea level changes, emphasizing the need for concrete evidence rather than philosophical musings.
  • Concerns are raised about the origins of water contributing to significant sea level rises, with some questioning the role of Antarctic and North American ice sheets in historical sea level changes.
  • Participants discuss the correlation between benthic foraminifera isotopes and sea level changes, noting that isotope data suggests earlier events of sea level rise than indicated by some graphs.
  • Some argue that the timing of sea level rise events does not align with the melting of known ice sheets, suggesting alternative explanations may be necessary.
  • Disagreement exists regarding the contributions of various ice sheets to sea level changes, with some asserting that the North American ice sheets could not have been the sole source of rapid sea level rise events.
  • References to recent modeling studies indicate that significant volumes of ice were present during the last glacial maximum, with varying contributions from different regions, including Eurasia and North America.

Areas of Agreement / Disagreement

Participants express multiple competing views on the causes and implications of historical sea level changes, with no consensus reached on the contributions of specific ice sheets or the validity of long-term predictions.

Contextual Notes

Limitations include uncertainties regarding the timing and sources of sea level rise, the reliability of paleo data, and the challenges in correlating ice sheet behavior across vast distances.

  • #31
Interesting thread, thank you. Sadly I lack the ability to extract the information I think I need and suspect it may be in the energy graphs above. So, if I may, I would like to ask a very hypothetical question:

Assuming current global energy levels are in balance, would it be possible to calculate, as a "forcing", the amount of energy needed to melt 96,983.8 cubic miles of ice and what would be the shortest timescale to achieve this?

Apologies if this is off topic or the wrong thread. The reason I ask is the many predictions of sea level rise being touted in the media. The latest, I read today, claimed the WWF is forecasting a 1 meter sea level rise in the next 10 years.

The ice figure above is my calculation ignoring the extra that would be required to fill low coastal areas. I am also assuming that ice already in the sea is not included. The melt must come from continental ice on Greenland and Antarctica. This also means the melt energy is provided by the atmosphere only.

I attempted to use the following:

The isothermal melting of ice requires some 334 kilojoules per kilogram at 273.16 K. At lower temperatures, it requires an average of some 2 kilojoules per degree more.

I calculated the total energy required and divided by ten to get the annual energy then divided that into the area of the planet to get watts per square meter. Problem is I am not sure I am going about this correctly. Also air melts ice from the top down, there is a limited contact area which I feel would have some effect on slowing down the energy transfer into the ice. How this would effect the timescale is beyond me.

Any thoughts or advice welcome.

Richard
 
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  • #32
Okay then. Here are the results of my calculations. I use the timescale of 10 years as this was the forecast from the WWF.

Using the value of 334 kilojoules per kilogram at 273.16 K to melt 96,983.8 cubic miles of ice I arrive at a figure of
382,216,079,803,280.4 joules per second to melt the ice over ten years.

This equates to a "forcing" of 0.75 watts per square meter. How this energy will be delivered to the ice in the required timescale I have no idea.
 

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