Amundsen Sea West Antarctic Ice Sheet History: development and sensitivity of the West Antarctic Ice Sheet tested from drill records of the Amundsen Sea Embayment1
Concerns about sea ice cover in the Amundsen Sea mandated the inclusion of many alternate sites for Expedition 379 in the original Scientific Prospectus (Gohl et al., 2017). The extraordinary ice cover in the Amundsen Sea during austral summer 2017/18 has prompted consideration of all possible alternates in case extreme sea ice conditions occur again in early 2019. In response to this, the following actions have been taken:
- Four new alternate sites on the continental rise farther away from the sea ice edge of season 2017/18 have been added to the science and operational plans to maximize the range of options in the Amundsen Sea. These are proposed Sites ASRE-07A, ASRE-08A, and ASRE-09A on the eastern Amundsen Sea rise and ASRW-02A on the western Amundsen Sea rise (Table T1; Figure F1; see Site summaries).
- Permission was obtained to occupy a range of locations along the seismic lines at each proposed site to provide for greater operational flexibility in case local ice conditions require it. These are presented in Table T2.
- Alternative drilling areas in regions adjacent to the Amundsen Sea have been added in case the Expedition 379 operations cannot take place as planned. These include sites approved as part of International Ocean Discovery Program (IODP) Proposal 732 offshore of the Antarctic Peninsula and in the Bellingshausen Sea sites and sites in Ross Sea not completed during Expedition 374 (Figures F2, F3) (see McKay et al., 2017a, 2017b, 2018). These are proposed Sites BELS-01A, BELS-02C, BELS-03B, PEN-01B, PEN-02C, PEN-03C, PEN-04B, and PEN-05D, as well as RSCR-10A, RSCR-15A, RSCR-18A, and RSCR-19A (see Site summaries).
- Although unrelated to sea ice issues, the approved depth of penetration has been increased for the following two Amundsen Sea sites: proposed Site ASSW-01B is now approved to 700 m, and proposed Site ASSE-03B is now approved to 1000 m.