Publication Date:
2018-08-10
Description:
A 1138-meter sediment core (AND-2A) recovered from the Southern McMurdo Sound sector of the Ross Sea
comprises a near-continuous record of Antarctic climate and ice sheet variability through the Early to early Middle
Miocene (20.2 to 14.5 million years ago), including an interval of inferred sustained global warmth known
as the Miocene Climatic Optimum (MCO). The record preserves 55 sedimentary sequences that reflect cycles of
glacial advance and retreat. A new analysis of proxy environmental data from the AND-2A core, and synthesis
with regional geological information, show that the early to middle Miocene Antarctic climate ranged from cold
polar conditions, similar to Antarctica during the Holocene, to those that characterise modern sub-polar environments.
Four disconformities that punctuate the sedimentary sequence coincide with regionally mapped seismic
discontinuities and reflect transient expansion of marine-based ice across the Ross Sea. The timing of these major
marine-based ice sheet advances correlates with shifts in highly-resolved deep sea isotope records and major drops
in eustatic sea-level indicating the global nature of these events. In contrast, three distinct intervals in the core
indicate that this high latitude site was periodically influenced by an ice sheet margin that had retreated beyond the
coastline. These relatively large-scale changes in climate and ice sheet extent occurred under atmospheric carbon
dioxide concentrations that generally varied between 300 to 500 ppm. Therefore, our reconstructions suggest that
Antarctica’s climate and ice sheets were sensitive to modest changes in greenhouse gas forcing and support previous
studies, which indicate that marine-based portions of theWAIS and EAIS can retreat under climatic conditions
that were similar to those projected for our future under current levels of atmospheric CO2.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Conference
,
notRev
Format:
application/pdf
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