Antarctic Circumpolar Current

Antarctic Circumpolar Current
NASA · Public domain · source
Name	Antarctic Circumpolar Current
Caption	Schematic of oceanic circulation around Antarctica
Location	Southern Ocean

Contents

Antarctic Circumpolar Current The Antarctic Circumpolar Current (ACC) is the dominant oceanic flow encircling Antarctica within the Southern Ocean, connecting the Atlantic Ocean, Indian Ocean, and Pacific Ocean. As the largest and strongest current system on Earth, the ACC plays a central role in global Oceanic circulation and planetary heat transport, influencing patterns observed in El Niño–Southern Oscillation, Southern Annular Mode, and polar climate variability. Its dynamics have been central to research by institutions such as the Scripps Institution of Oceanography, Woods Hole Oceanographic Institution, British Antarctic Survey, and Lamont–Doherty Earth Observatory.

Introduction

The ACC flows eastward around Antarctica along the polar front and the Antarctic Convergence and is bounded by bathymetric features like the Drake Passage, Kerguelen Plateau, and South Scotia Ridge. It interacts with ice shelves adjacent to Antarctic Peninsula, Ronne Ice Shelf, and Ross Ice Shelf, while mediating exchanges with the Southern Ocean Gyre and subpolar gyres linked to the Brazil Current, Agulhas Current, and East Australian Current. Oceanographic surveys by vessels such as RV Polarstern and RV Nathaniel B. Palmer and satellites operated by National Aeronautics and Space Administration and European Space Agency have mapped its extent.

The ACC exhibits strong zonal jets and mesoscale eddies influenced by topography at gaps including the Drake Passage, Tasman Rise, and Kerguelen Plateau. Wind forcing from the Southern Hemisphere Westerlies and modes like the Southern Annular Mode drive Ekman transport and baroclinic instability, producing fronts such as the Subantarctic Front, Polar Front, and Southern ACC Front. The ACC’s transport, estimated in Sverdrups, is constrained by geostrophic balance and potential vorticity conservation described in theories developed at Princeton University and University of Cambridge. Mesoscale variability studied with Argo floats coordinated by Global Argo and instruments from National Oceanic and Atmospheric Administration reveals jets comparable to those in the Gulf Stream and Kuroshio Current.

The ACC emerged with Antarctic glaciation driven by plate tectonics including the opening of the Drake Passage and Tasmanian Gateway and changes associated with the breakup of Gondwana and motion of the Antarctic Plate. Atmospheric shifts tied to Paleogene cooling and the uplift of the Andes influenced wind patterns that established the westerlies. Modern forcing involves interactions among Southern Hemisphere Westerlies, air–sea fluxes monitored by World Meteorological Organization networks, and buoyancy forcing studied in climate models developed at Met Office Hadley Centre, National Center for Atmospheric Research, and Max Planck Institute for Meteorology.

The ACC organizes water masses including Antarctic Surface Water, Subantarctic Mode Water, Intermediate Water, Antarctic Intermediate Water, Circumpolar Deep Water, and Antarctic Bottom Water. These water masses mediate carbon and nutrient cycles through processes observed in time-series programs like SOCCOM, Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP), and the Joint Global Ocean Flux Study. Upwelling of Circumpolar Deep Water supplies iron and macronutrients to phytoplankton blooms linked to regions near the Kerguelen Plateau, Crozet Islands, and Prince Edward Islands, affecting biogeochemical budgets tracked by researchers at Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory.

By controlling thermal advection and sea surface temperature gradients, the ACC affects ecosystems from krill assemblages studied by the Scientific Committee on Antarctic Research to apex predators documented by researchers at British Antarctic Survey and University of Tasmania. Its role in carbon sequestration links to global carbon budgets assessed by the Intergovernmental Panel on Climate Change and influences atmospheric CO2 on glacial–interglacial timescales investigated by paleoceanographers at University of Cambridge and Columbia University. Variability in the ACC modulates sea-ice distribution proximate to Weddell Sea, Amundsen Sea, and Ross Sea with ramifications for shipping near Antarctic Peninsula and for fisheries managed under the Convention for the Conservation of Antarctic Marine Living Resources.

Exploration of the Southern Ocean by voyages such as those of James Cook set early observations that were expanded by expeditions including the Challenger Expedition and research campaigns by Discovery Investigations. Modern methods combine hydrographic sections from GO-SHIP, autonomous profiling by Argo floats, gliders deployed by Monterey Bay Aquarium Research Institute, satellite altimetry from TOPEX/Poseidon and Jason series, and paleoclimatic reconstructions using sediments cored under programs like International Ocean Discovery Program. Analytical frameworks from institutions such as Scripps Institution of Oceanography and Woods Hole Oceanographic Institution underpin current understanding.

Human activities—shipping through Drake Passage, climate-driven changes tied to anthropogenic greenhouse forcing examined by Intergovernmental Panel on Climate Change, and fisheries regulated by Commission for the Conservation of Antarctic Marine Living Resources—impact ACC-mediated ecosystems. Conservation efforts include marine protected areas in the Ross Sea Marine Protected Area and initiatives led by Convention on Biological Diversity and Scientific Committee on Antarctic Research. Scientific diplomacy through the Antarctic Treaty System and logistical support by countries such as Australia, United Kingdom, United States, Argentina, and Chile facilitate monitoring, while policy frameworks at United Nations Framework Convention on Climate Change address long-term threats.