In the Bering Sea, or North Pacific in general, what was the farthest
south that sea ice extended (the ice limit)during the past 100,000
years.

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Request for Question Clarification by pafalafa-ga on 04 May 2006 18:12 PDT

dagstone-ga,

I'm not entirely sure what you're asking.

During the ice age, sea level was considerably lower, and many land
areas were exposed that are, today, under water.  This formed the
so-called Bering land bridge between Russia and Alaska.

Of course, there was a heck of a lot of ice, as well, and the glaciers
extended way down into the mid-section of the continental US.

But you asked specifically about "sea ice".  Can you clarify what it
is you're after here?

Thanks,

pafalafa-ga

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Request for Question Clarification by answerfinder-ga on 05 May 2006 00:59 PDT

Dear dagstone-ga,

The only map I have been able to find is for 18000 years ago. It is
part of the PALEOMAP Project and shows the sea ice in the North
Pacific did not extend as far south as that of the North Atlantic.
http://www.scotese.com/lastice.htm

Let me know whether this answer your question.

answerfinder-ga

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Clarification of Question by dagstone-ga on 05 May 2006 04:48 PDT

Currently in the Bering Sea sea ice forms to latitude 59 but is
generally only solid at latitude 62 and beyond unless it's within 100
or so km or land.  During the past 100,000 years how much further
south would sea ice have formed?   With the lowered sea levels due to
the water locked in glaciers and ice fields and the overall lowered
temperatures it's seems logical that sea ice should have
formed/extended further south.  How much further?

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Request for Question Clarification by pafalafa-ga on 05 May 2006 07:24 PDT

The consensus seems to be that sea ice extended at least as far south
as latitude 55, at the Umnak Plateau, and perhaps farther.

The presence of sea ice is inferred largely from the phytoplankton
makeup from a rather limited number of core samples, so there isn't a
great deal of precision in the estimate.

If you'd like, I can point you to some maps and some resources on this
topic, along with some researchers who you may wish to contact.


Let me know what you think.


pafalafa-ga

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Clarification of Question by dagstone-ga on 05 May 2006 13:59 PDT

Thanks answerfinder-ga.  It's a good graphic (one I didn't find) but
I'd like more specifics as to actual latitudes and times.

Thanks pafalafa-ga.  That gets me in the ballpark and any additional
sources (living, electronic or paper) would be appreciated.

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Request for Question Clarification by pafalafa-ga on 06 May 2006 13:57 PDT

dagstone-ga,

Thanks for the feedback on the earlier information I posted...glad to
know it meets your needs...or at least gets you in the ballpark.

I'll certainly add more detail, but it may be Monday before I am able
to get back to you on this.

If you're under a real time crunch, though, please let me know.

Stay tuned...

pafalafa-ga

dagstone-ga,

Hello again, and thanks for your patience on this.


The main paper I came across addressing the historical extent of sea
ice is this one:



http://instaar.colorado.edu/AW/abstract_detail.php?abstract_id=56
Rising temperatures, shrinking ice: the deglaciation in the Bering Sea
based on diatoms, alkenones, and oxygen isotopes


The paper is based on an analysis of ice cores taken from the Umnak
Plateau in the Bering Sea, at a latitude of 54 degrees 55 minutes.


Some relevant excerpts from the paper are:



...A realistic approximation of Bering and Chukchi sea-ice cover
throughout the Holocene and earlier is vital to our understanding of
current regional and hemispheric climate change.


...Fragilariopsis species have higher abundances until about 15 ka
suggesting the presence of seasonal sea ice before deglaciation.


...This first laminated interval probably represents a period when the
Umnak Plateau was situated at the maximum limit of ice encouraging
extremely high productivity during the spring bloom.

...Before 13 ka, ice advanced beyond the Umnak Plateau seasonally 

...Since 13 ka, our record does not provide conclusive evidence that
seasonal sea ice has advanced as far south as the Umnak Plateau



By the way, a frequently-cited paper on this topic (and one I couldn't
find a copy of online) is this one:


Sancetta, C. and Robinson, S.W., 1983, Diatom Evidence on Wisconsin
and Holocene Events in the Bering Sea: Quaternary Research, v. 20, p.
232-245.


It may be worth a visit to the library to try and track this down.


Lastly, the map at this site (Figure 30):


http://esp.cr.usgs.gov/research/alaska/alaskaC.html


appears to show the sea ice extending down to about latitude 55,
though it is not explicitly labeled as such.



I trust this information fully answers your question.


However, please don't rate this answer until you have everything you
need.  If there's anything more I can do for you, just post a Request
for Clarification, and I'm happy to assist you further.

pafalafa-ga


search strategy -- Google searches on:

"sea ice" bering "ice age"

"sea ice" bering wisconsin

umnak


"sea ice" bering wisconsin