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

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?

--
Alan LeHun

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)

"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

"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

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

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.

60 My BP would have seen very different ocean currents.. Wonder how
redistribution of heat worked then?


Richard Webb

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
Geologyecember 2004 Vol. 32, No. 12, pp. 1049-1052.

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
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