Ross Ice Shelf Oxygen Isotopes and West Antarctic Climate History

The Ross Ice Shelf δ 18 O profile at station J-9 covers at least the last 30,000 yr. It identifies the depth in the core of ice from (i) the last glacial-interglacial transition (266 to 286 m) and (ii) the 1000-m surface elevation (about 140 m). Various processes contribute to the δ 18 O change observed in the core: (i) climatic warming, mainly caused by a decrease in winter sea ice extent around Antarctica of about 6° latitude early in the glacial-interglacial transition, (ii) decreasing ice sheet thickness later in the glacial-interglacial transition and during the Holocene, and (iii) decreases in elevation and effective distance from the open ocean as the source of the ice in the core shifts along the flow line toward J-9. Average δ 18 O values of the last 3000 yr imply a fairly stable climate. Yet shorter (10 2 to 10 3 yr) δ 18 O climatic oscillations up to 6‰ are seen in both the Holocene and the glacial portion of the record.