Therefore, large uncertainties of about 50% of the calculated values thus exist owing as well to sparsely long-term measured data (see Supplementary Methods). Moreover, changes in ACC strength on the glacial-interglacial timescale correspond to the sea salt sodium (ssNa) flux record from the East Antarctic Dronning Maud Land (EDML) ice core (Fig. Updates? Compared to the Holocene, our data imply a stronger ACC prevailed during the last, warmer-than-present interglacial35. The Antarctic Circumpolar Current (ACC) is the most important current in the Southern Ocean, and the only current that flows completely around the globe. Rhs, S., Schwarzkopf, F. U., Speich, S. & Biastoch, A. Nathan Bindoff receives funding from Australian Research Council through its Discovery and Centre of Excellence programs and from the National Environment Science Program and the Antarctic Climate Ecosystems CRC. Numerical and analytical models have led to substantial advances with regard to the theory and dynamics of the ACC, and its links to the meridional circulation. Rev. There is a relatively small addition of flow in the Indian Ocean, with the transport south of Tasmania reaching around 147Sv, at which point the current is probably the largest on the planet. Antarctic Circumpolar Current Transport Variability during - AMETSOC ADS 7, 113116 (2014). Dashed line is production ratio (231Pa/230Th=0.093), suggesting no transport. Surface sediment characteristics related to provenance and ocean circulation in the Drake Passage sector of the Southern Ocean. The effect of sea ice on the flow depends on the ratio of ice floes to patches of open water5,16,52. In the meantime, to ensure continued support, we are displaying the site without styles Bond, G. et al. The timing of major ACC changes follows Antarctic temperature variations34, implying the ACC strength in the Drake Passage is sensitive to large-scale Southern Hemisphere climate oscillations (Fig. W.X. Google Scholar. Ocean Conveyor Belt - National Geographic Society Geol. North Atlantic ocean circulation and abrupt climate change during the last glaciation. The sea is releasing carbon dioxide. S.W. Antarctic circumpolar current's role in the Antarctic ice system: An Antarctic Circumpolar Current | Direction, Location, Map, & Facts & Armand, L. Sea-surface temperature and sea ice distribution of the Southern Ocean at the EPILOG Last Glacial Maximuma circum-Antarctic view based on siliceous microfossil records. Corrections? PubMed The Antarctic Coastal Current, also known as the East Wind Drift Current, is the southernmost current in the world. 11, 853859 (2018). a Antarctic temperature changes from the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core47. The changes south of the PF are small and were not considered for this estimation (see Fig. X.Z. PubMed The white dotted line marks the average modern winter sea ice edge68. 5c, d). Omissions? Although the intensity and position of the glacial SWW remain uncertain, a northward displacement of the SWW is widely assumed during the LGM38,39, with reduced impact on the ACC in the Drake Passage5,6,8. Nat. High-resolution records of grain size and Zr/Rb ratios can thus provide a robust signature of ACC variability. Upwelling of deep water under the sea ice brings substantial amounts of nutrients. a Range of modern Drake Passage cumulative volume transport from south to north along Jason Track 10436 and SR1b69. We use changes in grain size and geochemical properties of the terrigenous sediment fraction to reconstruct changes in ACC strength (Fig. 260, 340354 (2007). Antartic Circumpolar Current. Such presumption would be consistent with modern ACC volume transport and highest current velocities prevailing within the multiple jets of the SAF and PF in the Drake Passage region18,27,36. However, the relative contribution of these two water routes for the upper branch of AMOC has rarely been addressed in the past20,57. a Oxygen isotope record from North Greenland Ice Core Project (NGRIP, 18O vs. VSMOW)70. b Bermuda Rise 231Pa/230Th proxy for the AMOC strength44,59,60. Gray dots indicate Scotia Sea transect cores south of the Polar Front5. IRD fluctuations are overwhelmingly independent of \(\overline{{{{\rm{SSFS}}}}}\) changes with short-term exceptions at 2224ka and in the oldest part beyond ~134ka (Supplementary Fig. H.W.A., N.N., F.L., and S.W. Volume susceptibility on core PS97/085-3 was performed with a Bartington MS2E sensor and MS2 control unit on a split-core logger in 1mm intervals and a sensor amplitude resolution of 105 (SI-Units). Still further south lies the PF, which is marked by a transition to very cold, relatively fresh, Antarctic Surface Water at the surface. Both are known to split into two or three branches in some parts of the Southern Ocean, and merge together in other parts. 4e). Therefore, we estimate an equivalent reduction for the ACC volume transport during glacial periods delivering 8829Sv. J. Geophys. LynchStieglitz, J., Ito, T. & Michel, E. Antarctic density stratification and the strength of the circumpolar current during the Last Glacial Maximum. Oceans 96, 26752692 (1991). Antarctic Circumpolar Current - Division of Geological and Planetary Res. We found significant glacial-interglacial changes of ACC flow speed, with weakened current strength during glacials and a stronger circulation in interglacials. Differences between these glacial-interglacial changes are likely due to the geographical settings within latitudinal subdivisions of the ACC and the related fronts (Fig. Here a temperature minimum is allowed by salinity dominating density stratification, due to the lower temperatures. Geosci. The Funding information section was missing from this article and should have read Open Access funding enabled and organized by Projekt DEAL. [3] The eastbound clipper route, which is the fastest sailing route around the world, follows the ACC around three continental capes Cape Agulhas (Africa), South East Cape (Australia), and Cape Horn (South America). High-frequency variability in millennial-scale ACC changes prevailed during the glacial periods, but the ACC flow speed maxima always remained below ~15cms1 during this interval (Fig. Shuzhuang Wu. Geochem. [17], An expedition in May 2008 by 19 scientists[18] studied the geology and biology of eight Macquarie Ridge sea mounts, as well as the Antarctic Circumpolar Current to investigate the effects of climate change of the Southern Ocean. The Antarctic Circumpolar Current (ACC) is the dominant feature of ocean circulation in the Southern Hemisphere 1. [10] The isolation of Antarctica by the current is credited by many researchers with causing the glaciation of Antarctica and global cooling in the Eocene epoch. The Antarctic Circumpolar Current spans 8 of latitude or more, and its course varies slightly by location. Res. An alternative name for the ACC is the West Wind Drift. For instance, denser waters sit lower and lighter waters stand taller, and differences between the height of the sea surface give the speed of the current. X.F.Z. Paleoceanogr. f ACC bottom flow speeds were estimated by the correlation between the \(\overline{{{{\rm{SSFS}}}}}\) and adjacent current meter data (see Supplementary Fig. Antarctic sea ice control on ocean circulation in present and glacial climates. Affected by adjacent landmasses, submarine topography, and prevailing winds, the Antarctic Circumpolar Current is irregular in width and course. 474, 397408 (2017). The increasing eastward momentum imparted by the winds causes water parcels to drift outward from the axis of the Earth's rotation (in other words, northward) as a result of the Coriolis force. The westerly winds make this slope steeper, and the ACC rides eastward along it, faster where the slope is steeper, and weaker where its flatter. Geophys Res Lett. McCave, I., Crowhurst, S., Kuhn, G., Hillenbrand, C. & Meredith, M. Minimal change in Antarctic Circumpolar Current flow speed between the last glacial and Holocene. The ACC has been known to sailors for centuries; it greatly speeds up any travel from west to east, but makes sailing extremely difficult from east to west, although this is mostly due to the prevailing westerly winds. Correspondence to NOAA/AOML Altimetry Products Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. Paleoceanogr. The Antarctic Circumpolar Current separates the Southern Ocean from the Atlantic, Pacific, and Indian oceans at 60 S latitude, which roughly coincides with the currents southern boundary. Published estimates of the onset of the Antarctic Circumpolar Current vary, but it is commonly considered to have started at the Eocene/Oligocene boundary. 3). Orbital and millennial Antarctic climate variability over the past 800,000 years. Google Scholar. Nature 431, 147151 (2004). 4d). Sigman, D. M. & Boyle, E. A. Glacial/interglacial variations in atmospheric carbon dioxide. Res. Oceans https://doi.org/10.1029/2008JC005108 (2009). Article The northern boundary of the ACC is defined by the northern edge of the SAF, this being the most northerly water to pass through Drake Passage and therefore be circumpolar. The northward-flowing current off the east coast of the Antarctic Peninsula carries cold Antarctic coastal water into the circumpolar belt. Since our site is ~400km away from the South American continent and Antarctica, the terrigenous sand fractions are most likely transported by various processes (including sea ice, icebergs, etc.) The Antarctic Circumpolar Current (ACC) is the Earth's strongest ocean current (137-162 sverdrup (Sv)) flowing eastward along a 20,000 km pathway around Antarctica (Rintoul et al., 2001; Sokolov and Rintoul, 2009).Owing to the absence of land barriers, the ACC is the only ocean current connecting the Pacific, the Atlantic and the Indian oceans, and consequently influences . 1). Although the Antarctic Circumpolar Current (ACC) is the longest and the strongest oceanic current on the Earth and is the primary means of inter-basin exchange, it remains one of the most poorly understood components of global ocean circulation. The Agulhas leakage reached its transient transport maximum during the terminations, with subsequently significantly decreased water volume transport to the South Atlantic (~8Sv during MIS 5) during interglacials61. Wu, S. et al. Nat. On glacial-interglacial timescales, a weaker ACC in combination with a more extensive sea ice cover likely resulted in more sluggish deep waters and a stratified glacial circulation mode with a more isolated lower cell as detected by specific Nd-isotope values in deep-sea corals53 and Pb- and Nd-isotopic composition of authigenic Fe-Mn oxyhydroxide sediment coatings54. The Antarctic Circumpolar Current, or ACC, is the strongest ocean current on our planet. & Friedrich, T. Timing and magnitude of Southern Ocean sea ice/carbon cycle feedbacks. Biological and physical controls in the Southern Ocean on past millennial-scale atmospheric CO2 changes. Changes in ACC transport through the cold water route, together with the Agulhas leakage via the warm water route, have been suggested to regulate the AMOC strength6,20,21. 9). A more reliable quantification of the ACC in the Drake Passage would require long-term current meter records, which are presently not available, and at sites where grain-size measurements exist or will be studied. A total of 1520 samples were taken in 1cm intervals from core PS97/085-3 for grain-size measurements with a CILAS 1180L laser diffraction particle-size analyzer (CILAS, Orleans, France) at the AWI, Sylt. That single current moves more water than all the rivers on the planet combined. Geochim Cosmochim. Instead there has been an increase in eddies that move heat towards the pole, particularly in hotspots such as Drake Passage, Kerguelen Plateau, and between Tasmania and New Zealand. 2). The Drake Passage is the major bottleneck (Fig. Senior Research Fellow, Institute for Marine and Antarctic Studies, University of Tasmania, Professor of Physical Oceanography, Institute for Marine and Antarctic Studies, University of Tasmania. The age model is based on a combination of paleomagnetic excursions, relative paleointensity (RPI), radiocarbon dates, and tuning of high-resolution XRF scanning-derived calcium to titanium ratios (ln(Ca/Ti)) to Antarctic temperature anomalies (see Supplementary Methods; Supplementary Table1). L.D. Nature 428, 834 (2004). The Antarctic circumpolar current that swirls around Antarctica is the piston in the pump that drives worldwide ocean circulation patterns. a NGRIP oxygen isotope record70. Res. https://doi.pangaea.de/10.1594/PANGAEA.923843, https://doi.org/10.1038/s41467-021-27840-1, https://doi.org/10.1038/s41561-021-00699-z, http://creativecommons.org/licenses/by/4.0/, Evidence for late-glacial oceanic carbon redistribution and discharge from the Pacific Southern Ocean, Cancel https://doi.org/10.1002/2016GL070319 (2016). The Antarctic Circumpolar Current (ACC) is the main oceanographic feature of the Southern Ocean, flowing clockwise around Antarctica and connecting the Atlantic, Pacific, and Indian Ocean basins. Another cyclonic gyre occurs north of the Ross Sea. 8). The Antarctic Circumpolar Current (ACC) links the Atlantic, Pacific, and Indian Ocean basins, a 24 000-km-long current system (Olbers et al. Core PS97/085-3 is located in the central Drake Passage (red star), ~40km north of the Polar Front (see Supplementary Fig. 3d). 4f) with the atmosphere over millennial timescales. Sokolov, S. & Rintoul, S. R. Circumpolar structure and distribution of the Antarctic Circumpolar Current fronts: 1. The current is in a region of the world with intense winds and wave action. Antarctica has lost 3 trillion tonnes of ice in 25 years. J Climate, https://doi.org/10.1175/JCLI-D-19-0877.1 (2020). The ACC connects the Atlantic, Pacific, and Indian Oceans, and serves as a principal pathway of exchange among them. Geosy. Koenig, Z., Provost, C., Park, Y.-H., Ferrari, R. & Sennchael, N. Anatomy of the Antarctic Circumpolar Current volume transports through Drake Passage. The chronology of this latter core has been published before and is used here without modification23. Antarctic: Ocean Circulation - Dive & Discover 9). As a result, both the surface and deep waters flow from west to east around Antarctica. The contribution of Antarctic Bottom Water circulation to the modern ACC is modest, but potentially increased during glacial periods when expanded sea ice favored its production and increased its salinity12,40. 10, 593610 (1995). c Planktic foraminiferal fauna reflect the intensity of the Agulhas leakage58. ISSN 2041-1723 (online). 5d). Drouin, K. L. & Lozier, M. S. The surface pathways of the South Atlantic: revisiting the cold and warm water routes using observational data. The record shows a ~8cms1 increase in the ACC from the PGM to MIS 5e, larger than the LGM to Holocene increase of ~5cms1. The ACC is not immune to climate change. 2a, c, e). Paleoclimatol. Superimposed on the glacial-interglacial changes, our records exhibit marked high-amplitude, millennial-scale variations in the ACC flow speeds covering the last glacial cycle with highest amplitudes between MIS 4 and MIS 2 (Fig. Pap. It connects wind-driven surface circulation and thermohaline deep and bottom water circulation with impacts on global salinity, nutrients, dissolved gasses, and heat transport1,2. 5, 872875 (2012). The Antarctic Circumpolar Current (ACC) is the largest oceanic current system on Earth 1. Nat Geosci. Affected by adjacent landmasses, submarine topography, and prevailing winds, the Antarctic Circumpolar Current is irregular in width and course. 4g). Nature 407, 859 (2000). Map of the ocean surface temperature as measured by satellites and analysed by the European Copernicus Marine Services. We sincerely thank S. Wiebe and R. Frhlking-Teichert at the AWI for technical assistance in sample preparation, grain-size measurements, and XRF scans. Antarctic Circumpolar Current (West Wind Drift) The largest and most important ocean current in the southern hemisphere. It is the ACC that maintains this boundary. Changes in ACC strength could have regulated the Pacific-Atlantic exchange and caused variations in the chemical ventilation of the Drake Passage and South Atlantic water masses. The current is circumpolar due to the lack of any landmass connecting with Antarctica and this keeps warm ocean waters away from Antarctica, enabling that continent to maintain its huge ice sheet. The Antarctic Circumpolar Current (ACC) is a dominant feature of present-day ocean circulation and climate, influencing the strength of meridional overturning circulation, transition depth from surface to deep ocean, gas-exchange rate between atmosphere and deep ocean, and global surface heat distribution ( 1 - 4 ). Overall, a stronger ACC coincides with a weakened AMOC during cold phases in the Northern Hemisphere and warm intervals in the Southern Hemisphere (Fig. Furthermore, we found increasing amplitudes of ACC millennial-scale variations as the climate was approaching the LGM (~3823ka; Fig. But in the Southern Ocean, the momentum imparted to the surface waters cannot be offset in this way. 35, e2019PA003773 (2020). Such sizeable variability of seasonal sea ice is also documented in other diatom records from the Scotia Sea, which revealed seasonal sea ice shifts by up to ~8 latitude that have been attributed to changes in regional sea surface temperatures, and austral summer insolation forcing50. Smaller fluctuations in ACC changes (~2cms1, PS97/093-2) occurred in deep water (~3781m) near the SAF8. The sea ice extent around the antarctic continent for this day appears in light blue. Global ocean heat content in the Last Interglacial. This indicates that major changes in circum-Antarctic sea ice cover might have been linked to glacial-interglacial ACC strength changes, in line with earlier suggestions5,6. Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison. g 18O time series from the EDML ice core45. Scientists like us are studying the current to find out how it might affect the future of Antarcticas ice sheets, and the worlds sea levels. Vertical gray bars mark inferred glacial periods and pink bars indicate the sub-interglacial during Marine Isotope Stage (MIS) 5. Meredith, M. P. et al. https://doi.org/10.1029/2010GC003033 (2010). Sci. https://doi.org/10.1029/2012JD017630 (2012). from the continents and then reworked by bottom currents. d Glacial-interglacial (G-IG) flow speed differences associated with frontal system. 5d) with the Agulhas leakage intensity, reconstructed from planktic foraminiferal fauna census counts58 in the South Africa margin over the past 140ka (Fig. Although the ACC provided a dynamical link with the AMOC, several other important processes, like Southern Ocean wind-driven upwelling and buoyancy forcing2,14,42, may act together to explain the full changes of the AMOC. The ACC is critical to the global overturning circulation for two reasons. Larger glacial reductions of flow velocities are detected in north of the SAF (cores 1-4, see TableS2)6,7,8 and the PF (core 5, this study) compared to small changes south of the PF (cores 617;5 see Supplementary Table2). The region has lots of upwelling - very "rich" ocean basin (nutrients for plankton; food for higher-level feeders) Figure 9.16. & Andreas, E. L. A parametrization, based on sea ice morphology, of the neutral atmospheric drag coefficients for weather prediction and climate models. The ACC transports cold and fresh water from the Pacific to the Atlantic through the Drake Passage, known as cold water route19. McCave, I. N. & Andrews, J. T. Distinguishing current effects in sediments delivered to the ocean by ice. The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise (as seen from the South Pole) from west to east around Antarctica. New oceanic data on the structure and variability of the Antarctic Circumpolar Current (ACC) in the Drake Passage and its interaction with the atmosphere have revealed a more complex . Science 353, 470474 (2016). 13, 628633 (2020). The images or other third party material in this article are included in the articles Creative Commons license, unless indicated otherwise in a credit line to the material. The ACC flows eastward about 23, 000 km around Antarctica on the polar axis between 40 and 60 degrees south latitude, where there is . Quat. Core PS67/197-1 in the Scotia Sea is sensitive to changes in winter sea ice extent22. The Subantarctic Front to the north and Polar Front further south are the two main fronts of the ACC (the black lines in the images). A comparison of our ACC strength record to a high resolution carbonate saturation reconstruction from the Subantarctic South Atlantic49 indicates a correspondence of stronger ACC with reduced carbonate saturation during the major Antarctic warm intervals (Fig. To trace it starting arbitrarily at South America, it flows through the Drake Passage between South America and the Antarctic Peninsula and then is split by the Scotia Arc to the east, with a shallow warm branch flowing to the north in the Falkland Current and a deeper branch passing through the Arc more to the east before also turning to the north. 2f). The circumpolar current is driven by the strong westerly winds in the latitudes of the Southern Ocean. Antarctic Circumpolar Current picking up speed | Polarjournal The original article has been corrected. Such theories link the magnitude of the Circumpolar Current with the global thermohaline circulation, particularly the properties of the North Atlantic. 2f and Supplementary Fig. Rintoul, S. R. The global influence of localized dynamics in the Southern Ocean. While every effort has been made to follow citation style rules, there may be some discrepancies. Rev. 165 million to 182 million cubic metres of water every second, Antarctica has lost 3 trillion tonnes of ice in 25 years. Nature 517, 7376 (2015). Rev. Extremes in total ACC volume transport were estimated over some weeks during a 20-year period with maximum 166Sv and minimum 105Sv and a mean of 140Sv62. 201604910671). Here we identify a recurring phytoplankton bloom in the high-nutrient, low-chlorophyll waters of the Antarctic Circumpolar Current in the Pacific sector of the SO, that we argue is fed by iron of. 5b). Jack London's story "Make Westing" and the circumstances preceding the mutiny on the Bounty poignantly illustrate the difficulty it caused for mariners seeking to round Cape Horn westbound on the clipper ship route from New York to California. Yet, we still do not know accurately the magnitude of its volume transport: The two most recent observational programs in Drake Passage, DRAKE and cDrake, yielded transport values of 141 and 173.3 Sv (1 Sv = 10 6 m 3 /s), respectively. A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-27840-1. The age model is based on a combination of radiocarbon dates, paleomagnetic excursion, correlation of RPI of core PS97/085-3 with the RPI stack and tuning from high resolution XRF-CS ln (Ca/Ti) (Supplementary Table1). Lemke and C. Tiemann, Gesundheit Nord Bremen, are gratefully acknowledged for providing facilities and supporting the computed tomography measurements. High-resolution reconstructions of the ACC flow speed at the entrance of Drake Passage (MD07-3128) and on its northern continental slope (MR0806-PC09) extend only back to ~65ka but show substantial glacial decreases6. Dypvik, H. & Harris, N. B. Geochemical facies analysis of fine-grained siliciclastics using Th/U, Zr/Rb and (Zr+Rb)/Sr ratios. Google Scholar. Mean circumpolar paths. Abrupt changes in the southern extent of North Atlantic Deep Water during DansgaardOeschger events. Southern Ocean - an overview | ScienceDirect Topics 2e). We thus chose to investigate potential regional amplification effects of sea ice changes on millennial-scale ACC dynamics, as the EDML ssNa flux did not indicate hemispheric-wide sea ice variations34 on these time-scales. In practice both the thermohaline and the eddy/meander mechanisms are likely to be important. 2 and 3). 1. SAF Subantarctic Front, PF Polar Front, SACCF southern ACC Front. 8). https://doi.org/10.1038/s41467-021-24264-9, DOI: https://doi.org/10.1038/s41467-021-24264-9. PubMed Central Therefore, for our maximum velocity calculations during peak warm interglacials like MIS 5e we assume a total volume transport through Drake Passage of about 166Sv. Martin, T., Steele, M. & Zhang, J. Seasonality and long-term trend of Arctic Ocean surface stress in a model. analyzed the data. https://doi.org/10.1038/s41561-021-00699-z (2021). We acknowledge support by the Open Access Publication Funds of Alfred-Wegener-Institut Helmholtz-Zentrum fr Polar- und Meeresforschung. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Diekmann, B. et al. Article Marshall, J. 2004), composed of a series of filaments or fronts in temperature and salinity where most of the velocity is concentrated (Orsi et al.1995), plus a strong eddy field. Also known as: ACC, Circumpolar Current, West Wind Drift. Adv Space Res. Jouzel, J. et al. Language links are at the top of the page across from the title. Part I: Oceanographic Res. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Xiao, W. et al. Geophy. 4d). The bulk of the transport is carried in the middle two fronts. Rev. Southern Hemisphere westerly wind changes during the Last Glacial Maximum: paleo-data synthesis. On the average, it flows westward and parallel to the Antarctic coastline. 3). Evaluating Zr/Rb Ratio From XRF Scanning as an indicator of grain-size variations of glaciomarine sediments in the Southern Ocean. Lamy, F. et al. 4 (Blackwell Science, Oxford, 2003).
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