https://doi.org/10.14379/iodp.sp.383.2018

International Ocean Discovery Program
Expedition 383 Scientific Prospectus

Dynamics of the Pacific Antarctic Circumpolar Current (DYNAPACC)¹

Published August 2018

Abstract

The Antarctic Circumpolar Current (ACC) is the world’s strongest zonal current system that connects all three major ocean basins of the global ocean and therefore integrates and responds to global climate variability. Its flow is largely driven by strong westerly winds and constricted to its narrowest extent in the Drake Passage. Transport of fresh and cold surface and intermediate water masses through the Drake Passage (cold-water route) strongly affect the Atlantic Meridional Overturning Circulation (AMOC) together with the inflow of Indian Ocean water masses (warm-water route). Both oceanographic corridors are critical for the South Atlantic contribution to AMOC changes. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, deep-sea drilling records of the Pacific sector of the ACC lack information on its Cenozoic paleoceanography. To advance our knowledge and understanding of Plio-Pleistocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO₂, International Ocean Discovery Program Expedition 383 proposes the recovery of 180 to 500 m long high-resolution Plio-Pleistocene sediment sequences at (1) three primary sites located on a cross-frontal transect in the central South Pacific (CSP) between the modern Polar Front (Site CSP-3A) and the Subantarctic Zone (Sites CSP-1A and CSP-2B), (2) two sites (CHI-1C and CHI-4B) at the Chilean margin, and (3) one site from the pelagic eastern South Pacific (ESP; Site ESP-1A) close to the entrance to the Drake Passage. The planned sites represent a depth transect from ~1100 m at the Chilean margin (Site CHI-4B) to >5000 m in the Bellingshausen Sea (Site CSP-3A) that will allow investigation of Plio-Pleistocene changes in the vertical structure of the ACC—a key issue for understanding the role of the Southern Ocean in the global carbon cycle. All of the six primary and eight alternate sites were surveyed with seismic lines in 2009–2010 and most recently in 2016. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic, carbonate, and opal-based proxies to address our objectives of reconstructing, with unprecedented stratigraphic detail, surface to deep ocean variations and their relation to atmosphere and cryosphere changes through stadial-to-interstadial, glacial-to-interglacial, and warmer-than-present time intervals.

¹Lamy, F., Winckler, G., and Alvarez Zarikian, C.A., 2018. Expedition 383 Scientific Prospectus: Dynamics of the Pacific Antarctic Circumpolar Current (DYNAPACC). International Ocean Discovery Program. https://doi.org/​10.14379/​iodp.sp.383.2018

This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.