International Journal of Marine Science, 2024, Vol.14, No.2, 51-56 http://www.aquapublisher.com/index.php/ijms 51 Scientific Review Open Access Exploring the Antarctic Circumpolar Current: A Five Million Year Climate Journey Synchronized with Earth's Orbital Symphony Lingfei Jin South China Sea Biological Research Center, Hainan Institute of Tropical Agricultural Resources, Sanya, 572025, China Corresponding author email: krislfjin@gmail.com International Journal of Marine Science, 2024, Vol.14, No.1, doi: 10.5376/ijms.2024.14.0007 Received: 28 Mar., 2024 Accepted: 10 Apr., 2024 Published: 15 Apr., 2024 Copyright © 2024 Jin, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Jin L.F., 2024, Exploring the antarctic circumpolar current: a five million year climate journey synchronized with earth's orbital symphony, International Journal of Marine Science, 14(1): 51-56 (doi: 10.5376/ijms.2024.14.0007) On March 27, 2024, Frank Lamy, Gisela Winckler, Helge W. Arz, and scientists from various global research institutions published a research paper in Nature titled “Five million years of Antarctic Circumpolar Current strength variability.” The research team, through analyzing sediment cores from the seafloor of the southern Pacific Ocean, unveiled the long-term variability of the Antarctic Circumpolar Current (ACC) strength since the late Neogene. As the largest oceanic current system on Earth, the ACC has profound effects on global climate patterns, ocean circulation, and the stability of the Antarctic ice sheet. The study found that over the past five million years, the strength of the ACC did not show a linear trend but experienced a shift from intensification to weakening over a scale of millions of years, closely related to Earth's orbital cycles and the reconfiguration of the Southern Ocean. This discovery provides important new insights into the role of the ACC in the global climate system and for predicting future climate change. 1 Analysis of Experimental Data In this study, scientists utilized two key sediment cores from the Southern Antarctic Zone (SAZ) at approximately 3 600 meters depth, gathered during the 383rd voyage of the International Ocean Discovery Program (IODP), sites U1540 and U1541. By analyzing the composition of microfossils, isotopes, and soluble salts within these sediment cores, the team was able to trace the changes in the ACC’s strength over the past five million years. Notably, these sedimentary records contain information on changes in both the ACC’s strength and the ocean surface temperature and salinity of the region, providing valuable data for understanding how the ACC responds to global climate changes. The study of sortable silt within the sediments allowed the team to infer variations in the speed of bottom water flow, a crucial indicator of ACC strength. The comprehensive analysis of these data revealed significant changes in ACC strength throughout past geological periods, offering a window into how the world’s largest oceanic current system responded to environmental transitions. Figure 1 depicts the simulated ocean velocity of the modern ACC at a depth of 100 meters, with blue representing weaker flows and white indicating stronger flows. This model, based on the Finite-volumE Sea ice–Ocean Model (FESOM2) under the ROSSBY4.2 setting, showed ACC fronts derived from satellite altimetry from north to south as follows: NB (north boundary), SAF (Subantarctic Front), PF (Polar Front), SACCF (Southern ACC Front), and SB (Southern Boundary). Core and drilling locations are marked with white stars, providing direct data support for studying changes in the ACC. Figure 2 shows the historical changes in temperature and atmospheric carbon dioxide content recorded in Antarctic ice cores, as well as the variations in ACC strength. The black and blue curves respectively represent temperature changes in the EPICA Dome C ice core and atmospheric CO2 concentrations, displaying notable glacial-interglacial cycles. The colored curves show the reconstructed values of ACC strength at different sites, indicating fluctuating trends over time. The changes in ACC strength are temporally correlated with the temperature and CO2 records, particularly a decrease in ACC strength during glacial periods and an increase
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