Antartica's Cenozoic ice and climate history

SUMMARY 

One of the most significant and pressing challenges for climate predictions is to resolve the unknown contribution of continental ice sheets to future sea-level rise. The marine-based West Antarctic Ice Sheet (WAIS), with much of its bed >1000 meters below sea-level, has the potential to provide a major contribution to sea-level rise over the next century and beyond. Therefore, understanding underlying processes, thresholds, and magnitudes of previous WAIS retreats and collapses, when global temperature and atmospheric CO2 levels were higher than today, is essential to guide numerical model improvement and better predict future sea-level rise. These scientific issues are highlighted in Climate and Ocean Change Challenges 1 and 2 of the 2013-2023 IODP Science Plan and the Denver-2012 prioritization of that plan by the US IODP community. 

The USSSP and MagellanPlus-funded Antarctica’s Cenozoic Ice and Climate History workshop (Texas A&M University, May 9-11, 2016) is part of a coordinated plan developed since 2009 by the Past Antarctic Ice Sheet Dynamics (PAIS) research program through the Scientific Committee on Antarctic Research (SCAR; www.scar.org), an International Council for Science (ICSU) committee, to stimulate Antarctic Margin Drilling Proposals. The workshop discussed the status of the Antarctic and Southern Ocean proposals currently in the IODP review system and highlighted the requirement of geographically diverse drilling transects because recent observation and modeling studies reveal a heterogeneous response of the Antarctic Ice sheet to oceanic and atmospheric forcing. 

Three drilling proposals (751 in the Ross Sea; 839 in the Amundsen Sea; and 732 in the Bellingshausen Sea and Antarctic Peninsula), approved by the Scientific Evaluation Panel and under consideration for scheduling by the JOIDES Resolution Facility Board (JRFB) at the time of the workshop, form a coherent West Antarctic Margin Portfolio of drillsites, that will illuminate the spatial and temporal variations of past Antarctic Ice Sheet dynamics and guide model skill for future predictions, by: 1) reconstructing the orbital-scale Cenozoic dynamics of the WAIS, 2) identifying drivers and their thresholds, especially of ocean forcing, for past WAIS retreat, and 3) assessing relationships between the Antarctic cryosphere, ocean circulation, and global climate. This is particularly timely because the 2015 UN Climate Change Conference in Paris requested that IPCC write a special report by 2020 to assess the climate impacts of climate stabilization at +2°C and +1.5°C and response of Antarctic Ice Sheets will comprise an important component of this report. The IODP expeditions will provide near-field ice sheet data to complement and constrain the far-field sea level and paleoceanographic data obtained by expeditions in the Southern Ocean.