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Grad student talk - Orbital and millennial climate variability recorded in ice core stable isotopes

Thursday, October 18, 2012, 4:30PM - 5:30PM


Brad Markle

Visiting graduate student


Mort Turner room

Northeast corner of RL-1

Full title: "Orbital and Millennial climate variability recorded in stable isotopes from a new Antarctic ice core record."

A new ice core from the West Antarctic Ice Sheet (WAIS) Divide provides the highest resolution record yet obtained of the last 70 thousand years of Southern Hemisphere climate. Recovered from the more dynamic side of the Southern Continent, the WAIS Divide record sheds new light on Antarctic climate variability during the last glacial period and transition to the Holocene. The stable water isotope record shows that transitional warming began in West Antarctica several thousand years earlier than continent-wide warming and, critically, not lagging carbon dioxide nor Northern Hemisphere temperature changes. We show that an abrupt increase in warming rate and accumulation at WAIS Divide is coincident with continent-wide warming and immediately follows a peculiar chemical horizon. The timing points to large scale changes in Southern Hemisphere ocean and atmospheric circulation. We also examine millennial climate variability during the last glacial period and identify an unexpected synchronicity between West Antarctic circulation changes and Northern Hemisphere climate during Dansgaard/Oeschger-Antarctic Isotope Maximum events. We hypothesize that tropical circulation changes link these disparate aspects of the climate system through atmospheric teleconnections.