A 350 ka record of climate change from Lake El'gygytgyn, Far East Russian Arctic: refining the pattern of climate modes by means of cluster analysis

Abstract. Rock magnetic, biochemical and inorganic records
of the sediment cores PG1351 and Lz1024 from Lake
El’gygytgyn, Chukotka peninsula, Far East Russian Arctic,
were subject to a hierarchical agglomerative cluster analysis
in order to refine and extend the pattern of climate modes
as defined by Melles et al. (2007). Cluster analysis of the
data obtained from both cores yielded similar results, differentiating
clearly between the four climate modes warm,
peak warm, cold and dry, and cold and moist. In addition,
two transitional phases were identified, representing the early
stages of a cold phase and slightly colder conditions during
a warm phase. The statistical approach can thus be used to
resolve gradual changes in the sedimentary units as an indicator
of available oxygen in the hypolimnion in greater detail.
Based upon cluster analyses on core Lz1024, the published
succession of climate modes in core PG1351, covering
the last 250 ka, was modified and extended back to
350 ka. Comparison to the marine oxygen isotope (�18O)
stack LR04 (Lisiecki and Raymo, 2005) and the summer
insolation at 67.5� N, with the extended Lake El’gygytgyn
parameter records of magnetic susceptibility (�LF), total organic
carbon content (TOC) and the chemical index of alteration
(CIA; Minyuk et al., 2007), revealed that all stages back
to marine isotope stage (MIS) 10 and most of the substages
are clearly reflected in the pattern derived from the cluster
analysis.