Source:
Coupled atmosphere-ice-ocean dynamics
in Dansgaard-Oeschger events
By Camille Le and Andreas Born,
Quaternary Science Reviews,
Jan 1, 2019
Dansgaard-Oeschger
events are examples
of abrupt natural
climate changes
in Earth's history.
They were discovered
using Greenland ice cores.
( Bond et al., 1993;
Dansgaard et al., 1993 ).
D-O events
of the last ice age
are among
the best studied
abrupt
climate changes,
yet a detailed
explanation
is still lacking.
That's true of all climate
change questions in
real climnate science.
Only junk climate science
has 'all the answers'.
D-O events
are most common
in the North Atlantic, with
large temperature swings,
on time scales of decades,
or shorter, between
persistent cold (stadial)
and warm (interstadial)
conditions.
They seem to be a
“spontaneous oscillation",
of the coupled atmosphere
-ice-ocean system
of the North Atlantic,
Nordic Seas and Arctic,
( as a group, often called
"The Northern Seas" ).
The overall time scale
of D-O events is not
consistent with any
strong external forcing,
such as solar variability.
Obviously,
the ocean
transports
tropical heat
poleward,
warming the
Arctic region.
D-O events
always occur
during cold
glacial times,
but not during
the warm
interglacials.
We have been living
in the relatively warm
Holocene interglacial
for about 10,000 years.
Interglacials
tend to last
10,000 to
15,000 years,
followed by
85,000 to
90,000 years
of the climate
getting colder.
The ice sheets of the
last ice age reached
their maximum extent
at Last Glacial Maximum
( LGM, 21,000 years ago )
when global ice volume
was equivalent to
110 to 130 meters
of sea level, most ice
in the Laurentide
ice sheet over
North America:
D-O events are
most clearly seen
in Greenland
ice core records,
showing huge
temperature
swings of 8 to
16 degrees C.
Consider that
global warming
since 1880
is claimed
to be
only about
+1 degree C.
-- the size of a
rounding error,
compared to a
D-O event.
Proxy evidence reveals
D-O signals extended
across the Northern
Hemisphere, and into
the Southern Hemisphere
too.