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Re: Climate and Biogeography of Maastrichtian North America



Hey Dan...

Yeah... paleoclimatology happens to be a thing of mine ;-)

Anyway, send what you work up my way... I'll be happy to give you my
two cents (for what it's worth). No problem.  And yes, there's a hand
full of workers out there tinkering with resolving the Cretaceous
ocean/climate system. Past few years have seen a surge in activity,
mostly due to the introduction of new methods, like improvements in
isotope analysis, which have given us a much higher degree of
resolution than previously available... Leaps in our understanding of
the current climate system has also helped (by-product of the interest
in global warming).  There's been a couple of K "consensus" papers
that have pulled together the conclusions of the past few decades...
What I posted, I know, I pulled from at least one of them that I read
a year or so ago... I just need to remember where in the hell I put
it...  Let me dig through my hard drive... I'll send you what I find.

Oh, and if you're interested in the latest ideas of what was going on
at the North Pole during the K, I made a ridiculously long post on the
DML a few months back... I happen to be a heretic that believes the
existence of semi-permanent sea ice was a near certainty during
certain periods of the K (and there were most definitely "alpine"
glaciers... and not just in the far northern mountains... There was a
talk at SVP 2010 that gave some good reasons to believe that the
southern emerging Rockies in NA, at the very least, received
snowfall)... http://dml.cmnh.org/2011Aug/msg00204.html

Kris


On Thu, Dec 22, 2011 at 8:23 AM, Daniel Bensen <bensen.daniel@gmail.com> wrote:
> Wow! This is excellent. I had no idea people were actually working on
> this question. I'll have to read this email more carefully and make up
> a new climate map (I can't do it now because of computer problems),
> but when I do, can I show it to you and get your feedback?
> (BTW I don't suppose anyone else has already done this work? Are there
> any references you can point me at?)
> Dan
>
> On Wed, Dec 21, 2011 at 8:18 PM, K Kripchak <saurierlagen1978@gmail.com> 
> wrote:
>> The Gulf Stream as we know it wasn't established during the K. So, I'd
>> shy away from using it and/or its effects in the Mesozoic.
>>
>> Off the top of my head… The thing to remember about the K ocean is
>> that unlike today, where large gyres dominate circulation, the K ocean
>> (and Paleogene) was filled with mesoscale eddies. Due to the lack of
>> constant Weasterlies (due to seasonal reversals of high lat pressure
>> systems, unlike today), there would have been no subtropical and polar
>> fronts in the ocean, no well-developed ocean pycnocline, and no
>> tropical subtropical gyres dominating ocean... only those mesoscale
>> eddies (for example, it's thought that a counter-clockwise eddy
>> existed off the west and east coasts of NA).  In fact, these eddies
>> probably were far from stable… The only steady ocean currents would
>> have been the equatorial systems which were forced by constant
>> Easterly winds.  At mid and high lats, however, the ocean would have
>> been filled with shallow eddies that were variable in both intensity
>> and position and would have been the means for transporting equatorial
>> heat northward.  The larger, more deeply penetrating eddies would have
>> been steered by bathymetry.  Furthermore, dramatically different ocean
>> water densities from those of today would have had a huge impact on
>> ocean circulations... K climate simulations indicate that for various
>> reasons, half of the entire ocean surface and deep water would have
>> had nearly the same density... Therefore, storm and wind-generated
>> eddies were the main pumps that moved water up and down the column
>> (unlike today's system driven by huge basin-crossing conveyors). This
>> eddy-ocean would have therefore lacked the highly-developed structure
>> we see in today’s stratified ocean... so the vertical circulation
>> would have been more local and chaotic. This happens to be a good
>> explanation for why there were periodic widespread anoxic events in
>> the K ocean. The present ocean structure is kept the way it is because
>> of constant wind systems, which in turn depend on the high degree of
>> stability in atmospheric pressure systems located in the polar
>> regions… which are forced by permanent icecaps... all of which the K
>> lacked…
>>
>> So anyway… There was no Gulf Stream.  The Gulf Stream came into being
>> only after North and South America were connected via the Isthmus of
>> Panama... a mere 5 mya.  Prior to that time, North and South America
>> were not connected... a gap called the Central American Seaway allowed
>> warm tropical waters to flow between the Atlantic and Pacific Oceans.
>> The formation of the Isthmus of Panama partitioned the Atlantic and
>> Pacific Oceans, fundamentally changing global ocean circulation, and
>> in consequence global climate/weather...  The Pacific and Atlantic
>> salinities, which were once nearly the same, greatly diverged, with
>> the Pacific becoming relatively fresher, salinity steadily increased
>> in the Atlantic (Trade Winds also came about at roughly this time),
>> and over time the new northward-diverted current called the Gulf
>> Stream intensified, transporting a more warm, salty water mass high
>> into northern latitudes, where it was cooled by Arctic winds until it
>> became dense enough to sink to the ocean floor... giving birth to the
>> Ocean Conveyor, which in turn intensified the Gulf Stream in a
>> feedback loop that pulled even more water northward.
>>
>> Kris
>>
>>
>> On Tue, Dec 20, 2011 at 2:55 PM, Renato Santos <dracontes@gmail.com> wrote:
>>> Dan,
>>>
>>> It really depends on the ocean currents,
>>> http://en.wikipedia.org/wiki/File:Corrientes-oceanicas.gif , and
>>> prevailing winds, http://en.wikipedia.org/wiki/Atmospheric_circulation
>>> : if there was a Gulf Current established by then I would expect a
>>> similar climate pattern, albeit accommodating for the interior sea
>>> way, with a tropical southeastern coast drying progressively
>>> northwards and inland.
>>>
>>> --
>>> Renato Santos
>>> http://dracontes.deviantart.com