Evidence for Climate Teleconnections Between Greenland and the Sierra Nevada of California During the Holocene, Including the 8200 and 5200 Climate Events - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 204

In contrast to the usual lake charcoal record, the charcoal
pattern derived from Coburn Lake was strongly episodic.
Prior to 1500 years ago, there was little background charcoal
deposited between peaks (Figure 4). I elected to compare
charcoal peaks from Coburn Lake with ACCEs rather than
with millennial-scale climate changes, as is most commonly
done, because of the episodic nature of the Coburn Lake
charcoal record and because of the large number of radiocar-
bon dates available.
Correlating charcoal peaks with ACCEs also challenges
the conventional wisdom for many within the sediment char-
coal community that individual charcoal peaks should not be
said to represent individual ACCEs. This conventional wis-
dom is based on the fact that individual charcoal peaks are
not well correlated with individual ACCEs in most charcoal
records. If a few charcoal peaks are correlated with known
ACCEs, most are not. Therefore, those few that are correlated
are suspected of being correlated purely by chance.
Exceptions are studies by Meyer et al. [1995] and Pierce et
al. [2004] in which individual charcoal lenses from within
hillside debris

off the coast of Santa Barbara have found evidence for corre-
lations with Greenland suggesting global-scale changes in
atmospheric circulation [Kennett and Ingram, 1995; Behl and
Kennett, 1996; Hendy and Kennett, 1999; Haug et al., 2001;
Hendy et al., 2002; Friddell et al., 2002; Roark et al., 2003].
Wagner et al. [2005] found isotopic changes in Arizona that
closely mirrored the Dansgaard-Oeschger (D-O) events re-
corded in Greenland ice cores. Dean [2007] suggested cli-
mate teleconnections between the margins of Alta and Baja
California and Greenland covering the past 60,000 years.
Farther south, Peterson et al. [2000], Lachniet et al. [2005],
and Stott et al. [2002] found close synchronicity between
records collected from off the coast of Venezuela, the western
coast of Costa Rica, and the western Pacific tropical warm
pool, respectively, and D-O events in Greenland.
To the north, Pisias et al. [2001] suggested that coastal
upwelling, temperatures, and vegetation along the Oregon
coast were correlated with the same D-O events. Hu et al.
[2003] demonstrated synchronicity between climate records
in Alaska and Greenland spanning the Holocene. In the Great
Basin, Benson et al. [1997, 1998], Lin et al. [1998], and Zic
et al. [2002] found evidence for teleconnections with Green-
land from Owens and Mono Lakes, California; Searles
Lakes, California; and Summer Lake, Oregon, respectively.
The Atlantic-centered Atlantic Multidecadal Oscillation
(AMO) has been associated with changes in the frequency
of United States droughts, droughts being more frequent or
more prolonged when the AMO is in its warm (positive)
phase. Two of the most severe droughts of the twentieth
century, the droughts of the 1930s and the 1950s, occurred
when the AMO was in a warm phase [Schubert et al., 2004].
Swetnam et al. [2006] found that fires across the western
United States over the past 500 years were most widespread
when the AMO was in a warm phase.
McCabe et al. [2004, 2008] found that the Pacific-centered
ENSO was also important in understanding drought occur-
rence in the contiguous United States. McCabe et al. found
that the Pacific Decadal Oscillation (PDO) cooling and the
AMO each accounted for half of the variance in multi-
decadal drought frequency. Kitzberger et al. [2007] found
that both the ENSO and PDO drove the frequency of recent

flow deposits were analyzed in relation to
relatively short-term climate changes. As with Coburn Lake,
charcoal deposition within these debris flows was episodic.
The Coburn Lake record has more in common with the
charcoal records from alluvial fans than it does the typical
lake charcoal record.
The Coburn Lake charcoal record is unusual in that all
charcoal peaks or increases in charcoal occurred at the be-
ginning of severe droughts and only at the beginning of
severe droughts over the past 1800 years. Fires from other
causes do not seem to be represented. The size and con gu-

ration of the Coburn Lake watershed, noted above in section
2, might contribute to understanding why Coburn Lake has
been so unusually sensitive to recording ACCE-linked res

while filtering out fires from other causes.

5.5.2. Evidence for interhemispheric teleconnections.
Though some remain skeptical, the evidence for teleconnec-
tions between climate events in the western United States
and the North Atlantic has increased to the point that more
researchers have come to acknowledge the evidence. As
noted in section 5.1.1, several researchers have published,
though not necessarily acknowledged, evidence for the 8200
[Meyer et al., 1995; Benson et al., 1997; Barron et al., 2003;
Potito et al., 2006] and 5200 [Meyer et al., 1995; Spooner et
al., 1997; Clark et al., 2002; Barron et al., 2003; Mensing et
al., 2004; Klem, 2010] ACCEs in the western United States
or British Columbia.
Numerous studies have recognized climate teleconnections
between Greenland and regions surrounding Coburn Lake. In
southern California, researchers studying sediments collected

fires in the western United States at interannual to decadal
time scales, but that the AMO determined the severity of
fires and how widespread fires were on multidecadal time
scales.
Seager et al. [2007] suggested that North American mega-
droughts during the Medieval period (A.D. 800 - 1300) also
occurred during cold La Ni a-like conditions in conjunction

with warm phases of the AMO. Feng et al. [2008] modeled
climate conditions during medieval droughts and found that
a cool tropical Paci

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c controlled drought intensity, a warm