Shuzhuang Wu. There would be changes in storm patterns over the continental areas, affecting the monsoon systems. Even though a full collapse of the AMOC within the next few decades isn't probable, it is possible, Goes said, and it could come with high risk. The breakthroughs and innovations that we uncover lead to new ways of thinking, new connections, and new industries. The tightest geographical constriction through which the current flows is Drake Passage, where only 800 km separates South America from Antarctica. We have observed much change already. It extends from the sea surface to the bottom of the ocean, and encircles Antarctica. I. 4d). . Res. Helen Phillips receives funding from Australian Research Council Discovery Projects and the Australian Government's National Environmental Science Programme, and is an Associate Investigator of the Australian Research Council Centre of Excellence in Climate Extremes. 474, 397408 (2017). ISSN 2041-1723 (online). Nature 428, 834 (2004). They can be invaluable in helping scientists better understand how the region has already changed as the world has warmed. 201604910671). The fact that, with continued warming, AMOC will slow down is a very robust result. Donohue, K., Tracey, K., Watts, D., Chidichimo, M. & Chereskin, T. Mean antarctic circumpolar current transport measured in Drake Passage. Some even explore beneath the sea ice. 5). Nature 431, 147151 (2004). When the RAPID array went online, the assumption was that itd take 40 years to get an idea of whether the current system was in decline. Compared to the Holocene, our data imply a stronger ACC prevailed during the last, warmer-than-present interglacial35. These strong variations of the ACC through the cold water route have been likely linked to high AMOC instability46,48 between MIS 4 and MIS 2 (Fig. The Antarctic Circumpolar Current (ACC) is the dominant feature of ocean circulation in the Southern Hemisphere 1. If it does, the melt would load the north Atlantic with astonishing amounts of freshwater, fast-tracking the decline of the AMOC and adding many feet to sea levels. e Relative abundance of diatom winter sea ice indicator Fragilariopsis curta group (F. curta+F. cylindrus) with three-point smoothing22,67. As the ancient water rises, shown here in yellow, over nearly a century, it circles the continent. 4 (Springer, 2003). Google Scholar. USA 117, 44984504 (2020). The AMOC "is a major tipping element in the climate system and a future collapse would have severe impacts on the climate in the North Atlantic region," the study says, adding that there has been other research in recent years indicating that its circulation is weakening. volume12, Articlenumber:3948 (2021) Gersonde, R. & Zielinski, U. Use of this site constitutes acceptance of our User Agreement and Privacy Policy and Cookie Statement and Your California Privacy Rights. 4d), in contrast to a steady decline of the Antarctic temperatures (Fig. Sources: Map data from the British Antarctic Survey, NASA Earth Observatory, Lamont-Doherty Earth Observatory of Columbia University, Natural Earth, Bright Earth e-Atlas Basemap. We used high-resolution grain-size data of the siliciclastic sediment fraction and X-ray fluorescence (XRF) scanning-based elemental ratios from a sediment core in the central Drake Passage (Site PS97/085; 58 21.28S, 62 10.02W; 3090m water depth; Fig. J.T. Res. 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. And it wasnt until 20 years ago that scientists deployed a dedicated AMOC sensor array, known as RAPID, which also measures current velocities and salinityanother factor that influences the density of water. She grew up in the Arctic, on the coast of the Chukchi Sea in Kotzebue, Alaska. This summer's extraordinary heat is but a preview of what's to come: Humidity not only makes daytime highs more miserable, it extends the hotness through the night. Accordingly, the \(\overline{{{{\rm{SS}}}}}\) may not capture the entire magnitude of the flow-speed variations in our record (Fig. Previous studies proposed that sea ice cover, in addition to wind stress, has a significant influence on the surface ocean drag coefficient on forcing the ocean surface layer and ultimately current speed5,6,16. The latest study makes no mention of the Gulf Stream, specifically, but because it is part of this system, it would be impacted by such a collapse. Rintoul, S. R. The global influence of localized dynamics in the Southern Ocean. By this teams calculations, the circulation could shut down as early as 2025, and no later than 2095. Paleoclimatol. It's just hard to tease apart, because we really don't know what the intrinsic timescales of AMOC are, says Nicholas Foukal, an assistant scientist at Woods Hole Oceanographic Institution, who wasnt involved in the new paper. Understanding the magnitude and sensitivity of the ACC during the geological past is fundamental for assessing its role in the global Meridional Overturning Circulation (MOC), in particular with regard to ongoing and future anthropogenic climate change. University of Tasmania provides funding as a member of The Conversation AU. The question now is how this increased transfer of heat across the ACC will impact the stability of the Antarctic ice sheet, and consequently the rate of global sea-level rise. Oceans absorb large amounts of these emissions, while also absorbing heat from the atmosphere, serving as a critical buffer against climate change and keeping the world from otherwise becoming a practically unlivable hothouse. Such a collapse could trigger rapid weather and climate changes in the U.S., Europe and elsewhere. Smaller fluctuations in ACC changes (~2cms1, PS97/093-2) occurred in deep water (~3781m) near the SAF8. Researchers are worried about the impact of climate change on this upwelling. Fischer, H. et al. 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. Orsi, A. H., Whitworth, T. III & Nowlin, W. D. Jr On the meridional extent and fronts of the Antarctic Circumpolar Current. Gottschalk, J. et al. https://doi.org/10.1038/s41561-021-00699-z (2021). In contrast to MIS 5e and the Holocene, the ACC strength significantly decreased during the Penultimate Glacial Maximum (PGM, ~140ka; \(\overline{{{{\rm{SSFS}}}}}\)=~27m) and the LGM sensu lato (~2818ka; \(\overline{{{{\rm{SSFS}}}}}\) =~32m). These glaciers act as buttresses, helping to hold back the massive ice sheets that cover the continent and that are slowly moving toward the ocean. But theyll keep coming, An abandoned arctic military base just spilled a scientific secret, See if you take a shine to our picks for the best sunglasses and sun protection, 2023 Cond Nast. 5c, d), suggesting that they both likely have induced a positive feedback to the AMOC recovering into a stronger interglacial mode as indicated by low 231Pa/230Th ratios44,59,60 (Fig. Moving northward, away from Antarctica, the water temperatures. There, the ice shelves of two large glaciers, Thwaites and Pine Island, hold much of the regions ice sheet back. The Antarctic Circumpolar Current (ACC) is the world's strongest ocean current. It is also changing as the world's climate warms. Along the continental shelf, centuries-old water from deep beneath the worlds oceans rises toward Antarctica. This system of currents, known as the Atlantic Meridional Overturning Circulation, or AMOC, moves 15 million cubic meters of water per second. Antarctica is the only continent that has an ocean current circulating completely around it. In contrast, the Drake Passage throughflow remained strong throughout MIS 5, with smaller sub-interglacial fluctuations (Fig. Deacon and his fellow voyagers were hardly the first to experience the hardships of the Southern Ocean. It extends from the sea surface to the bottom of the ocean, and encircles Antarctica. 13, 628633 (2020). 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. e Mean grain size of sortable silt and fine sand (\(\overline{{{{\rm{SSFS}}}}}\), 10125m) was used as the ACC flow speed proxy in this study. Gray dots indicate Scotia Sea transect cores south of the Polar Front5. Southern Hemisphere westerly wind changes during the Last Glacial Maximum: model-data comparison. c Saturation index as a proxy for reconstructed carbonate saturation changes in the South Atlantic49. Scientists are watching with bated breath to see if ice will return to normal levels. Of particular interest to Dr. Russell and others are acidity readings, because they can be used to determine the waters carbon dioxide content. (The Ditlevsens are siblings. Combining our ACC flow speed proxies with sea-ice reconstructions enables us to investigate millennial-scale ACC variations, potentially linked to Antarctic winter sea ice changes during the last glacial period. Correspondence to Chem. For the last glacial termination, the AMOC shutdown44 during Heinrich Event 1 reinforced the insolation-driven initial Southern Hemisphere deglacial warming45. 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. The animation also shows another feature of the global ocean circulation: the Antarctic Circumpolar Current. Nat. The effect of sea ice on the flow depends on the ratio of ice floes to patches of open water5,16,52. Abrupt changes in the southern extent of North Atlantic Deep Water during DansgaardOeschger events. 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. Scientists are continuing to monitor the system to learn what they can about its current state. This system, along with other ocean currents, is crucial to helping maintain the Earth's climate and scientists believe it is being affected by climate changee, asmelting icealters the balance in northern waters. Article They have discovered that global warming is affecting the Antarctic current in complex ways, and these shifts could complicate the ability to fight climate change in the future. The Arctic Is a Freezer Thats Losing Power. 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. Paleoclimatol. Larger glacial-interglacial changes in flow speeds were observed north of the SAF with a range of ~513cms1 (MD07-3128, MR0806-PC9, and GC528) at intermediate water depths (~6001030m)6,7. Surface sediment characteristics related to provenance and ocean circulation in the Drake Passage sector of the Southern Ocean. As the ice thins, the glaciers lose some of their ability to keep the ice sheets in check. This chapter describes the Antarctic circumpolar current (ACC) system.

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