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Abstract # PP41A-0629
Jumbo piston core NBP0003-38, a 20.53 meter core from the Vega Drift (Erebus and
Terror Gulf, northeastern Antarctic Peninsula), contains a high resolution record
of climate extending back ~8500 years. Lithologic and foraminiferal data presented
previously document mid-Holocene conditions warmer than today. These data include
increased clay concentration, higher concentrations of ice-rafted debris, and
higher magnetic susceptibility below ~6000 ybp, the consequence of extensive
meltwater and iceberg calving. This change in lithology is accompanied by the
presence of a benthic foraminferal assemblage characteristic of the western
Antarctic Peninsula, as contrasted to a lower productivity assemblage observed
in the upper section of core. New diatom data confirm mid-Holocene warmth, as
based on analysis of the distribution of the two varieties of the species
Eucampia antarctica. They are distinguished by their symmetry, with the
asymmetric E. antarctica var. antarctica characteristic of subpolar waters
and the symmetric E. antarctica var. recta a polar form. Increased relative
abundance of the sub-polar form occurs between ~4000-7000 ybp, overlapping and
then post-dating the time interval characterized by increased ice melt. In
addition, the ratio of terminal to intercalary valves was analyzed. A direct
consequence of chain length, a function of the amount of growth, this ratio
has been used to record oscillations in winter sea ice cover. Data from JPC38
show longest chain lengths (and least winter sea ice) from ~4000-7000 ybp, in
concert with the dominance of the sub-polar form of the species. These data
suggest the possibility that mid-Holocene warmth at this site was associated
with the southward migration of sub-polar waters and consequently less winter
sea ice.
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