Evolution and forcing mechanisms of El Nino over the past 21,000 years

• Published in: Nature
• Main Authors: Liu, Zhengyu, Lu, Zhengyao, Wen, Xinyu, Otto-Bliesner, B. L., Timmermann, A., Cobb, K. M.
• Other Authors: Liu, ZY (reprint author), Univ Wisconsin, Dept Atmospher & Ocean Sci, Madison, WI 53706 USA., Univ Wisconsin, Dept Atmospher & Ocean Sci, Madison, WI 53706 USA., Univ Wisconsin, Nelson Ctr Climat Res, Madison, WI 53706 USA., Peking Univ, Sch Phys, Lab Climate Ocean & Atmosphere Studies, Beijing 100871, Peoples R China., Natl Ctr Atmospher Res, Climate & Global Dynam Div, Boulder, CO 80307 USA., Univ Hawaii Manoa, Int Pacific Res Ctr, Honolulu, HI 96822 USA., Univ Hawaii Manoa, Dept Oceanog, Sch Ocean & Earth Sci & Technol, Honolulu, HI 96822 USA., Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA.
• Format: Journal/Newspaper
• Language: English
• Published: nature 2014
• Subjects: EASTERN TROPICAL PACIFIC; SOUTHERN-OSCILLATION; LAST DEGLACIATION; ICE-AGE; CLIMATE; VARIABILITY; HOLOCENE; ENSO; MODEL; MIDHOLOCENE; Pacific; Ice Sheet
• Online Access: https://hdl.handle.net/20.500.11897/295926; https://doi.org/10.1038/nature13963

The El Nino Southern Oscillation (ENSO) is Earth's dominant source of interannual climate variability, but its response to global warming remains highly uncertain(1). To improve our understanding of ENSO's sensitivity to external climate forcing, it is paramount to determine its past behaviour by using palaeoclimate data and model simulations. Palaeoclimate records show that ENSO has varied considerably since the Last Glacial Maximum (21,000 years ago)(2-9), and some data sets suggest a gradual intensification of ENS 0 over the past 6,000 years(2'5'7'8). Previous attempts to simulate the transient evolution of ENSO have relied on simplified models(10) or snapshot(11-13) experiments. Here we analyse a series of transient Coupled General Circulation Model simulations forced by changes in greenhouse gasses, orbital forcing, the meltwater discharge and the ice-sheet history throughout the past 21,000 years. Consistent with most palaeo-ENSO reconstructions, our model simulates an orbitally induced strengthening of ENSO during the Holocene epoch, which is caused by increasing positive ocean-atmosphere feedbacks. During the early deglaciation, ENSO characteristics change drastically in response to meltwater discharges and the resulting changes in the Atlantic Meridional Overturning Circulation and equatorial annual cycle. Increasing deglacial atmospheric CO2 concentrations tend to weaken ENSO, whereas retreating glacial ice sheets intensify ENSO. The complex evolution of forcings and ENSO feedbacks and the uncertainties in the reconstruction further highlight the challenge and opportunity for constraining future ENSO responses. Multidisciplinary Sciences SCI(E) 2 ARTICLE [e-mail] 7528 550-+ 515