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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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![]() 18:00 15Dec2004 RTRS-Arctic Ocean was balmy 70 mln years ago -study LONDON, Dec 15 (Reuters) - It may be freezing cold and covered in ice now but 70 million years ago the Arctic Ocean was as tepid as the Mediterranean. In a past greenhouse world, the frigid north would have been balmy, judging from evidence in a core drilled in an ice island drifting over a ridge on the ocean floor. Hugh Jenkyns, of the University of Oxford in England, and scientists from the Royal Netherlands Institute for Sea Research analysed organic material in mud in the core and calculated that the mean sea surface temperature of the Arctic Ocean was 15 degrees Centigrade (59 Fahrenheit) about 70 million years ago. "Further back in time if would have been even warmer, so it would have been a good place to swim," said Jenkyns, who reported the findings in the journal Nature on Wednesday. Twenty million years earlier it could have reached 20 degrees Centigrade (68F). "It was certainly very much a greenhouse world," he told Reuters. Although the scientists don't know why it was so warm, they suspect it may have been due to high concentrations of atmospheric carbon dioxide, the greenhouse gas blamed for contributing to current global warming. In a commentary in the journal, Christopher Poulsen, of the University of Michigan in the United States, said the levels of carbon dioxide were probably three to six times what they are today which contributed to a "super-greenhouse climate". "For a region blanketed in darkness for half of the year, the Arctic Ocean was astoundingly warm," said Poulsen. --------------------------------- My comment.... Ever heard of precession? Surely the wobbling of the earth's axis would affect the angle of theEarth's tilt pointing perhaps more directly towards the sun. Brendan |
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In article ,
Alan LeHun writes: In article , says... My comment.... Ever heard of precession? Surely the wobbling of the earth's axis would affect the angle of theEarth's tilt pointing perhaps more directly towards the sun. And what of the med.? What sort of SST's did they have 70M years ago? I'm not sure that the Med existed 70 million years ago. -- John Hall "Sir, I have found you an argument; but I am not obliged to find you an understanding." Dr Samuel Johnson (1709-1784) |
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![]() "Brendan DJ Murphy" wrote in message ... 18:00 15Dec2004 RTRS-Arctic Ocean was balmy 70 mln years ago -study (snip) My comment.... Ever heard of precession? Surely the wobbling of the earth's axis would affect the angle of theEarth's tilt pointing perhaps more directly towards the sun. Brendan Brendan By precession do you mean the normal definition of the term (the 26,000 year rotation of the direction of the earth's axis around the normal to the orbital plane, which would cause no climatic change), or do you mean to refer either to a change in the inclination of the earth's axis to the orbital plane (which would effect seasonal weather extremes at polar latitudes) or to a movement of the north and south poles relative to the surface of the earth? I am not sure how the latter could be correlated to continental drift, or whether it would be a slower or faster movement. Of course the oceans might have been balmy for quite different reasons. Regards, Roger |
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![]() "Roger Smith" wrote in message ... "Brendan DJ Murphy" wrote in message ... 18:00 15Dec2004 RTRS-Arctic Ocean was balmy 70 mln years ago -study (snip) My comment.... Ever heard of precession? Surely the wobbling of the earth's axis would affect the angle of theEarth's tilt pointing perhaps more directly towards the sun. Brendan Brendan By precession do you mean the normal definition of the term (the 26,000 year rotation of the direction of the earth's axis around the normal to the orbital plane, which would cause no climatic change), or do you mean to refer either to a change in the inclination of the earth's axis to the orbital plane (which would effect seasonal weather extremes at polar latitudes) or to a movement of the north and south poles relative to the surface of the earth? I am not sure how the latter could be correlated to continental drift, or whether it would be a slower or faster movement. Of course the oceans might have been balmy for quite different reasons. Regards, Roger Yes :-p |
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In article , nospam_nov03
@jhall.co.uk says... And what of the med.? What sort of SST's did they have 70M years ago? I'm not sure that the Med existed 70 million years ago. lol. Indeed, maybe not, but I'm sure there would have been large bodies of tropical and sub-tropical waters which would have been proportionally warmer than polar waters. If it was 15deg at 90deg what was it at 0deg? -- Alan LeHun |
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Precession, as you imply has no effect on the climate, but changes in the
tilt of the axis certainly do. This has a period of about 41000 years. The variation is not large, 21.8 to 24.2 degrees, roughly, and it seems that low values are more associated with ice ages owing to the relatively low insolation in summer in high latitudes. The eccentricity of the earth's orbit is also quite a factor, and can be much higher than the present value of 0.0167. Its effect depends on the position of the perihelion with respect to the equinoxes. I'm not certain that even now, despite advances in celestial mechanics, either the eccentricity or tilt are known accurately back to 70 million years ago. Tudor Hughes, Warlingham, Surrey. |
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60 My BP would have seen very different ocean currents.. Wonder how
redistribution of heat worked then? Richard Webb |
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60 My BP would have seen very different ocean currents.. Wonder how
redistribution of heat worked then? Richard Webb The polar warmth during the Cretaceous is one of the unsolved problems of paleoclimatology. Kerry Emmanuel has proposed that the atmosphere and hurricane activity may have been at least partly responsible. Also see- http://www.gsajournals.org/gsaonline...130%2FG20828.1 Geology ![]() Evidence for increased latent heat transport during the Cretaceous (Albian) greenhouse warming D.F. Ufnar et al The mid-Cretaceous was a time of greenhouse warmth with reduced equator-to-pole temperature gradients. Ancient soil carbonates formed in coastal plain deposits throughout the North American Western Interior Basin and North Slope, Alaska, have been used to reconstruct aspects of the mid-Cretaceous hydrologic cycle. Stable isotope mass-balance modeling suggests that the hydrologic cycle was greatly intensified with enhanced precipitation and evaporation rates. The intensified hydrologic cycle has implications for global heat transfer during greenhouse phases of Earth history. Quantitative estimates suggest that 2-4 times as much latent heat was transferred toward the poles with an intensified hydrologic cycle. The increased heat transfer through the atmosphere coupled with ocean heat transport and increased atmospheric carbon dioxide levels may help explain the polar warmth during the mid-Cretaceous. -- regards, david (add 17 to waghorne to reply) |
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