Palynological Indexes as Proxies of Millennial- to Decadal-Scale Climate Change in Temperate and Arctic Regions
Sarah J. Fowell
Data from Mongolia demonstrate the
use of customized palynological indexes in reconstruction of millennial- to
decadal-scale perturbations in temperate steppe biomes. Palynological and sedimentological data from
cores of lake Telmen, in north-central Mongolia, reveal significant coherence
with respect to Late Holocene changes in moisture availability. Telmen is a saline, closed basin lake that
occupies an intermontane depression between the Hangai and Bulnay ranges. Although this basin has been covered by steppe
vegetation for the past ~7000 years, a semi-quantitative pollen index based on
the ratio of characteristic dry steppe taxa (Artemisia and Chenopodiaceae) to common meadow-steppe and
forest-steppe taxa of the family Poaceae permits identification of humid and
arid intervals. Correspondence between
low values of this palynological index, intervals of laminated sediments,
flooding, and lake highstands validates use of the index as a proxy for
moisture availability in the Telmen region.
Maximum humidity is recorded between ~4060-1650 14C yr B.P. Additional humid intervals encompass the
Medieval Warm Epoch and the last centuries of the Little Ice Age.
Customized indexes that reflect
temperature and/or precipitation changes can also be employed to identify long-
and short-term, climate-driven changes in and between glacial steppe-tundra and
interglacial taiga or tundra vegetation of Alaska. Analysis of regional pollen rain deposited in the Gulf of Alaska
may provide answers to long-standing questions regarding the full glacial
vegetation of Beringia, the nature and duration of ecosystem response to
prehistoric volcanic eruptions, and the presence/absence of Younger Dryas
cooling and Medieval warming in Alaska.
Furthermore, recognition and dating of reworked fossil palynomorphs in
turbidites and pelagic sediments has the potential to permit identification of
rapidly eroding source rocks and regions of accelerated uplift in the Alaska
range.