A new paper published in Science magazine suggests that ocean the floors are getting deeper and sea levels have fallen by about 170 meters (560 ft) since the Cretaceous period 80 million years ago, due to tectonic shifts. Previous estimates were between 40 to 250 meters. On this basis of this work, a fall of 120 metres is expected over the next 80 million years, which equates to just 0.015 centimetres per century. Not much when we we consider IPCC projections of sea level rise. That said, the IPCC seems to have abandoned decadal projections in their latest report and gone for a 90-year projection, following the accuracy failures of the 1990, 1995 and 2001 reports. See the January 15th post over at Prometheus: Verification of IPCC Sea Level Rise Forecasts 1990, 1995, 2001.
The research article is entitled: 'Long-Term Sea-Level Fluctuations Driven by Ocean Basin Dynamics'
The first paragraph reads:
Earth's long-term sea-level history is characterized by widespread continental flooding in the Cretaceous period (145 to 65 million years ago), followed by gradual regression of inland seas. However, published estimates of the Late Cretaceous sea-level high differ by half an order of magnitude, from 40 to 250 meters above the present level. The low estimate is based on the stratigraphy of the New Jersey margin. By assimilating marine geophysical data into reconstructions of ancient ocean basins, we model a Late Cretaceous sea level that is 170 (85 to 270) meters higher than it is today. We use a mantle convection model to suggest that New Jersey subsided by 105 to 180 meters in the past 70 million years because of North America's westward passage over the subducted Farallon plate. This mechanism reconciles New Jersey margin–based sea-level estimates with ocean basin reconstructions.
The paper is also reported by Reuters, with their usual perspective on climate change.
“[Those] who have an excessive faith in their theories or in their ideas are not only poorly disposed to make discoveries, but they also make very poor observations.”
—Claude Bernard (1813-78) French physiologist, 1865.
Mr T,
your simplistic description of oceanic and continental crust tells me you don't.
One reason I ignore you.
So relieved we're on speaking terms again Louis 🙂
The oceanic crust is composed of sheeted dykes and pillow basalts. Quite clearly it exists and has a chemical composition very different to continetal crust. It is also a lot thinner (only a few km instead of 30+).
It's also exposed in New Zealand, Oman, Newfoundland, and Iceland (where you can see the mid-ocean ridge quite clearly, and even measure the rate of expansion.)
Falling is probably a poor term, sinking would be beter. And it can sink into the aesthenosphere, which is in a plastic state (similar to the mantle) - sinking of 170m is not that far.
Mr T,
Oceanic crust is firstly an oxymoron.
Fall to where?
And I have never accepted the theory of plate tectonics, not from some esoteric theoretical stance but from observation.
Louis, I thought you were ignoring me!
But seriously, aren't they talking about the ocean floor, the oceanic crust? Certainly that can fall. Unless of course you don't accept the theory of Plate Tectonics.
Or might it be a misplaced metaphor? Damn this cursed conundrum (loosely paraphrased from Macbeth).
Looks like our two experts here have not picked up on the non sequitur that no ocean can fall. Perhaps sea levels could but then, when a moron, what relevance are facts?
This seems to agree with ancient Perth Basin shorelines. I seem to recall that sea level was estimated at a bit over +200m for the Cretaceous.
What was the IPCC's claimed precision? You have to look at that before saying they were inaccurate.
"following the accuracy failures of the 1990, 1995 and 2001 reports." - come off it - I think most would be very happy with that result given the complexities.
It stands to reason that the continents are becoming progressively lighter with regard to the underlying lithosphere.