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 191

Evidence for Climate Teleconnections Between Greenland and the Sierra Nevada
of California During the Holocene, Including the 8200 and 5200 Climate Events

Stephen F. Wathen

Department of Plant Sciences, University of California, Davis, California, USA

cant impacts on environments and
human cultures in the past. The extent and potential causes of ACC events (ACCEs)
are thus important questions to explore. An 8500 year macrocharcoal record was
developed from Coburn Lake, Sierra Nevada, and compared with published high-
resolution paleoclimate and paleo

Abrupt climate change (ACC) has had signi

re records from the Sierra Nevada, eastern
Canada, and Greenland arriving at the following conclusions. Temperatures were
generally hot or rising at the beginning of long-term severe droughts (mega-
droughts) in the Sierra Nevada. For the most part, severe

res occurred at Coburn
Lake at the beginning of severe droughts, suggesting a response by vegetation and
slopes to ACC. There was also strong synchronicity between the beginnings of
droughts and

fire events in eastern Canada and
Greenland. Evidence is presented that (1) both the 8200 and 5200 ACCEs occurred
in the Sierra Nevada and (2) as severe droughts were beginning in the Sierra
Nevada, severe droughts were ending in Greenland. Coburn Lake charcoal peaks
were also synchronous with the general pattern of soot deposition onto Greenland,
reportedly from

fires at Coburn Lake and climate and

fires in eastern Canada, from 8500 to 3000 years ago. The begin-
nings of severe droughts in the Sierra Nevada were synchronous with charcoal
peaks in Lac Francis, Quebec, over the past 6750 years. This synchronicity in
climate and fire events suggests the possibility that abrupt, large-scale northward

and southward shifts in the locations of the northern Polar Front and subtropical
high-pressure zone accompanied the onset of ACCEs in the past.

1. INTRODUCTION matter of years or a few decades, such that societies or

ecosystems have little time to adapt and thus may undergo
signi

1.1. Abrupt Climate Change cant alteration or even collapse [Committee on Abrupt

Climate Change, National Research Council, 2002]. ACC
has been implicated in the collapse of many early complex
human societies [Douglas, 1988; Weiss, 2003; Leroya et al.,
2006]. Less is known, however, about the effect of past
ACCEs on natural ecosystems. The two most prominent
ACCEs within the Holocene period occurred at 8200 and
5200 cal years B.P. (calibrated years before present).

cant impacts
on natural environments and humans in the past. Thus, the
timing, extent, and potential causes of ACC are important
questions to investigate. ACC events (ACCEs) occur over a

Abrupt climate change (ACC) has had signi

1.1.1. The 8200 year abrupt climate change event. The
8200 year ACCE was probably the most severe ACCE