Onset and evolution of southern annular mode like changes at centennial timescale

• Published in: Scientific Reports
• Main Authors: Moreno Moncada, Patricio, Vilanova, I., Villa Martínez, R., Dunbar, R. B., Mucciarone, D. A., Kaplan, M. R., Garreaud Salazar, René, Rojas, M., Moy, C. M., De Pol-Holz, R., Lambert, F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2018
• Subjects: Antarctic; Southern Ocean; The Antarctic; Patagonia; Antarc*
• Online Access: https://doi.org/10.1038/s41598-018-21836-6; https://repositorio.uchile.cl/handle/2250/150432

The Southern Westerly Winds (SWW) are the surface expression of geostrophic winds that encircle the southern mid-latitudes. In conjunction with the Southern Ocean, they establish a coupled system that not only controls climate in the southern third of the world, but is also closely connected to the position of the Intertropical Convergence Zone and CO2 degassing from the deep ocean. Paradoxically, little is known about their behavior since the last ice age and relationships with mid-latitude glacier history and tropical climate variability. Here we present a lake sediment record from Chilean Patagonia (51°S) that reveals fluctuations of the low-level SWW at mid-latitudes, including strong westerlies during the Antarctic Cold Reversal, anomalously low intensity during the early Holocene, which was unfavorable for glacier growth, and strong SWW since ~7.5 ka. We detect nine positive Southern Annular Mode-like events at centennial timescale since ~5.8 ka that alternate with cold/wet intervals favorable for glacier expansions (Neoglaciations) in southern Patagonia. The correspondence of key features of mid-latitude atmospheric circulation with shifts in tropical climate since ~10 ka suggests that coherent climatic shifts in these regions have driven climate change in vast sectors of the Southern Hemisphere at centennial and millennial timescales. ICM grants P05–002 and NC120066, Fondap 15110009, DRI USA2013-0035, Fondecyt grants 1151469, 1131055, and 1151427, and NSF EAR-0902363 (M.R.K.). LDEO contribution #8188