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Australia: The Land Where Time Began |
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During the Transition from the Last
Interglacial to the Last Glacial Air-Sea Decoupling Occurred in Western
Europe An increase in summer insolation that occurred
between about 80,000-70,000 years ago controlled a period of continental
ice growth that was among the 4 largest expansions of ice over the last
250,000 years (Dansgaard, W. et
al.,
1998). The subpolar and northern subtropical regions of the Atlantic
Ocean have been proposed as the source of the moisture for the expansion
that occurred during the Marine Isotope Stage (MIS) 5a/4 transition
(Dansgaard, W. et al., 1998; Peterson et al., 2000). The mechanism responsible for
keeping the glaciers growing through 3 suborbital cooling events within
this period, which were associated with the discharge of icebergs into
the North Atlantic (Brook et al., 2000; Broecker, Peteet & Rind, 1985),
as well as the cooling over Greenland (Chiang & Bitz, 2005; Wang et al.,
2007) has remained uncertain. In this study the authors1
reconstructed parallel records of sea surface temperatures (SSTs) and
air temperatures based on data from marine microfossils and pollen,
respectively, obtained from sediment cores that collected within the
northern subtropical gyre. Throughout the MIS5a/4 transition the thermal
gradient between the cold air and the warmer sea increased, being marked
by 3 intervals during which the thermal gradients associated with C20,
C19 and C18’ cold events were even more pronounced. The warm surface of
the ocean along the margin of western Europe has been argued by the
authors1 to have provided a source of moisture that was
transported to feed the ice sheets in colder Greenland, northern Europe
and the Arctic by storms that were northward tracking.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |