Publication Date:
2018-09-11
Description:
The North Pacific is a zone of cyclogenesis that modulates synoptic-scale atmospheric circulation, yet
there is a paucity of instrumental and paleoclimate data to fully constrain its long-term state and variability. We present the first Holocene oxygen isotope record (d18Odiatom) from the Aleutian Islands, using
siliceous diatoms preserved in Heart Lake on Adak Island (51.85° N, 176.69° W). This study builds on
previous work demonstrating that Heart Lake sedimentary d18Odiatom values record the d18O signal of
precipitation, and correlate significantly with atmospheric circulation indices over the past century. We
apply this empirical relationship to interpret a new 9.6 ka d18Odiatom record from the same lake, supported
by diatom assemblage analysis. Our results demonstrate distinct shifts in the prevailing trajectory
of storm systems that drove spatially heterogeneous patterns of moisture delivery and climate across the
region. During the early-mid Holocene, a warmer/wetter climate prevailed due to a predominantly
westerly Aleutian Low that enhanced advection of warm 18O-enriched Pacific moisture to Adak, and
culminated in a d18Odiatom maxima (33.3‰) at 7.6 ka during the Holocene Thermal Maximum. After 4.5
ka, relatively lower d18Odiatom indicates cooler/drier conditions associated with enhanced northerly circulation that persisted into the 21st century. Our analysis is consistent with surface climate conditions
inferred from a suite of terrestrial and marine climate-proxy records. This new Holocene dataset bridges
the gap in an expanding regional network of paleoisotope studies, and provides a fresh assessment of the
complex spatial patterns of Holocene climate across Beringia and the atmospheric forces driving them.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
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