据了解，南极环极流（ACC）主导着南大洋（SO）周围的热、盐和示踪剂的转移，推动着南极洲周围富含碳的深水的上涌。古气候重建揭示了SO环流的显著变异性，然而，几乎没有记录将ACC流的定量重建与跨越多个更新世冰期循环的SO上升流示踪剂联系起来。
研究人员重建了非洲南部SO的近底部流速变化，揭示了ACC喷流强度和/或接近度的系统冰期-间冰期变化。这些是由比现在更温暖的“超级间冰期”叠加而成的，其中中纬度ACC（41°S）的极端减速与高纬度ACC （>54°S）的更快流动相反，这意味着ACC向极地加强。
结合地下深层稳定碳同位素梯度的重建，研究人员发现，ACC的重组与南极洲周围同位素轻的深水上涌相吻合，这可能是造成间冰期大气二氧化碳(CO2)水平升高的原因。
附：英文原文
Title: Shifting Antarctic Circumpolar Current south of Africa over the past 1.9 million years
Author: Aidan Starr, Ian R. Hall, Stephen Barker, Alexandra Nederbragt, Lindsey Owen, Sidney R. Hemming
Issue&Volume: 2025-01-03
Abstract: The Antarctic Circumpolar Current (ACC) dominates the transfer of heat, salt, and tracers around the Southern Ocean (SO), driving the upwelling of carbon-rich deep waters around Antarctica. Paleoclimate reconstructions reveal marked variability in SO circulation; however, few records exist coupling quantitative reconstructions of ACC flow with tracers of SO upwelling spanning multiple Pleistocene glacial cycles. Here, we reconstruct near-bottom flow speed variability in the SO south of Africa, revealing systematic glacial-interglacial variations in the strength and/or proximity of ACC jets. These are superimposed by warmer-than-present “super-interglacials,” whereby extreme slowdown in the midlatitude ACC (41°S) is opposed by faster flow at higher latitudes (>54°S), implying poleward strengthening of the ACC. Coupled with reconstructions of the subsurface-deep stable carbon isotope gradient, we show that the reorganization of ACC coincides with the upwelling of isotopically light deep waters around Antarctica, likely contributing to the interglacial rise in atmospheric carbon dioxide (CO2) levels.
DOI: adp1692
Source:https://www.science.org/doi/10.1126/sciadv.adp1692