Re: Mesozoic snow - refined

[Phil Bigelow <bigelowp@juno.com>]

The currents and the temperature flux of the Interior Seaway can only be
hypothesized.  There was a paper published a few years ago on this very
subject (using computer modeling, as I recall).  Various scenarios were
discussed.  Once scenario involved a current pattern and temperature
similar to that of today's Gulf Stream.

Today's Gulf Stream does strange things to northern Europe.  Palm trees
grow in western Ireland.  Citizens of Narvik, Norway bring picnic lunches
to the beach on New Year's Day.

Did a north polar ice cap exist during the Maastrictian?  Possibly.  The
north end of the Interior Seaway had finally closed off, and warm Tethyan
water could no longer flow northward to moderate the Arctic Ocean
temperatures (and cold Arctic Ocean water couldn't flow southward).

There are no modern analogs to the Maastrictian hydrosphere.  The only
large tropical epieric seas that exist today are found in the Indonesian
Archipelago and the waters between Australia and New Guinea, but neither
of these seas have the correct geometry and boundaries of the late
Mesozoic Interior Seaway.

If the Hell Creek area had a climate similar to today's coastal Florida
(and most people think it was similar), then depicting the Hell Creek
landscape as snowy during the winter would be an exaggeration of the
available evidence.  That is not to say that it didn't *occasionally*
snow in that area, but to portray the Hell Creek region that way is
stepping over the line a bit.

Most paleobotanical evidence points to a WORST-CASE winter temperature
regime for the Hell Creek region similar to today's coastal Olympic
Peninsula during the winter.  In other words, minimum temps. of 35-40s
F., with occasional dips below 32 degrees F. caused by high pressure
fronts coming from the continental interior.  "January" mean temps of
55-60 degrees F. would be more typical for the Hell Creek region.

IMHO, Atlanta, GA is only comfortable during the winter.  But I come from
the Pacific Northwet, so take my opinion with a grain of salt.

<pb>
--

On Wed, 07 Apr 2004 18:47:30 -0400 MariusRomanus@aol.com writes:
> Let's review what I already said...
> 
> GCMs, continental interiors, freezing temperatures in winter, large 
> seasonal variation in temperatures, climate not equitable, ice 
> rafted deposits through much of Phanerozoic, small ice sheets 
> favorable at high latitudes...
> 
> Granted, you'd have to take a few steps out side of the box in order 
> to apply what I said to the coastal regions of the interior seaway 
> during the esrly late Maastrichtian. All things considered, 
> seasonality within the vicinity of the seaway would have been 
> minimal. But, given the probable extent of the seaway at that time, 
> and the location of the Hell Creek formation, the occurrence of snow 
> was most definitely a viable possibility.
> 
> It's a meteorological truth; Cold air always wins. During the 
> winter, I should like to think that up north would have radiated out 
> enough to produce a dry continental polar air mass that would have 
> been cold enough to kick off snowfall as it moved south and 
> encountered that moist marine tropical air mass from the south. The 
> denser cold air stays at the surface and lifts the warm air aloft. 
> In other words, a cold front. The warm air adiabatically cools and 
> the moisture precips out directly into the cold air below. If the 
> air is freezing, you get snow. If the surface is freezing, you get 
> accumulation. If it snows long enough over that above freezing 
> surface, evaporative cooling will eventually drop the surface to 
> freezing and accumulation will take place. Even if you back off 
> slightly when it comes to the dynamics by weakening atmospheric 
> temperature contrasts, you'd still get the type of scenario, though 
> at a reduced scale. With a continental polar air mass during the 
> winter th!
> at was less potent than today's (the most-likely case), whenever a 
> surge of cold air advection took place, fronts and their precip 
> would push south, though they wouldn't have been as vigorous.
> 
> In any case, given the situation, such events normally wouldn't have 
> lasted for very long, with only a slight accumulation before the 
> pattern shifted enough to allow warm marine air to once again advect 
> north and into the region.
> 
> Kris
> http://hometown.aol.com/saurierlagen/Paleo-Photography.html
> 
> 



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