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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Antarctica
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Antarctic ice sheet (1)
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Asia
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Far East
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Japan
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Honshu (1)
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Indian Ocean
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Ninetyeast Ridge (1)
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International Ocean Discovery Program
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Expedition 353
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IODP Site U1443 (1)
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Kerguelen Plateau (1)
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Pacific Ocean
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East Pacific
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Northeast Pacific (1)
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Southeast Pacific
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Nazca Ridge (1)
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North Pacific
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Northeast Pacific (1)
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Northwest Pacific
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Japan Sea
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Yamato Rise (1)
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South China Sea (1)
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South Pacific
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Southeast Pacific
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Nazca Ridge (1)
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Southwest Pacific
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Tasman Sea (1)
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West Pacific
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Northwest Pacific
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Japan Sea
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Yamato Rise (1)
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South China Sea (1)
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Southwest Pacific
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Tasman Sea (1)
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elements, isotopes
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carbon
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C-13/C-12 (1)
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isotope ratios (1)
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isotopes
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stable isotopes
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C-13/C-12 (1)
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O-18/O-16 (1)
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oxygen
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O-18/O-16 (1)
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fossils
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Invertebrata
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Protista
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Radiolaria (2)
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microfossils (2)
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geologic age
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Cenozoic
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Quaternary
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Pleistocene (1)
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Tertiary
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Neogene
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Miocene
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middle Miocene (1)
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upper Miocene (1)
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Pliocene (1)
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Primary terms
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Antarctica
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Antarctic ice sheet (1)
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Asia
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Far East
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Japan
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Honshu (1)
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carbon
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C-13/C-12 (1)
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Cenozoic
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Quaternary
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Pleistocene (1)
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Tertiary
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Neogene
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Miocene
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middle Miocene (1)
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upper Miocene (1)
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Pliocene (1)
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climate change (1)
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Indian Ocean
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Ninetyeast Ridge (1)
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Integrated Ocean Drilling Program
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Expedition 346
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IODP Site U1425 (1)
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Expeditions 320/321
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Expedition 321
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IODP Site U1337 (1)
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IODP Site U1338 (1)
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-
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Invertebrata
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Protista
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Radiolaria (2)
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isotopes
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stable isotopes
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C-13/C-12 (1)
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O-18/O-16 (1)
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Ocean Drilling Program
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Leg 120
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ODP Site 751 (1)
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Leg 121
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ODP Site 758 (1)
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Leg 184
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ODP Site 1146 (1)
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Leg 189
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ODP Site 1171 (1)
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Leg 202
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ODP Site 1236 (1)
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ODP Site 1237 (1)
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oxygen
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O-18/O-16 (1)
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Pacific Ocean
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East Pacific
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Northeast Pacific (1)
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Southeast Pacific
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Nazca Ridge (1)
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-
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North Pacific
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Northeast Pacific (1)
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Northwest Pacific
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Japan Sea
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Yamato Rise (1)
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South China Sea (1)
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-
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South Pacific
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Southeast Pacific
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Nazca Ridge (1)
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Southwest Pacific
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Tasman Sea (1)
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-
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West Pacific
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Northwest Pacific
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Japan Sea
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Yamato Rise (1)
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South China Sea (1)
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Southwest Pacific
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Tasman Sea (1)
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paleoclimatology (2)
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sediments
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marine sediments (1)
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weathering (1)
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rock formations
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Monterey Formation (1)
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sediments
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sediments
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marine sediments (1)
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Middle Miocene climate–carbon cycle dynamics: Keys for understanding future trends on a warmer Earth?
ABSTRACT The late early to middle Miocene period (18–12.7 Ma) was marked by profound environmental change, as Earth entered into the warmest climate phase of the Neogene (Miocene climate optimum) and then transitioned to a much colder mode with development of permanent ice sheets on Antarctica. Integration of high-resolution benthic foraminiferal isotope records in well-preserved sedimentary successions from the Pacific, Southern, and Indian Oceans provides a long-term perspective with which to assess relationships among climate change, ocean circulation, and carbon cycle dynamics during these successive climate reversals. Fundamentally different modes of ocean circulation and carbon cycling prevailed on an almost ice-free Earth during the Miocene climate optimum (ca. 16.9–14.7 Ma). Comparison of δ 13 C profiles revealed a marked decrease in ocean stratification and in the strength of the meridional overturning circulation during the Miocene climate optimum. We speculate that labile polar ice sheets, weaker Southern Hemisphere westerlies, higher sea level, and more acidic, oxygen-depleted oceans promoted shelf-basin partitioning of carbonate deposition and a weaker meridional overturning circulation, reducing the sequestration efficiency of the biological pump. X-ray fluorescence scanning data additionally revealed that 100 k.y. eccentricity-paced transient hyperthermal events coincided with intense episodes of deep-water acidification and deoxygenation. The in-phase coherence of δ 18 O and δ 13 C at the eccentricity band further suggests that orbitally paced processes such as remineralization of organic carbon from the deep-ocean dissolved organic carbon pool and/or weathering-induced carbon and nutrient fluxes from tropical monsoonal regions to the ocean contributed to the high amplitude variability of the marine carbon cycle. Stepwise global cooling and ice-sheet expansion during the middle Miocene climate transition (ca. 14.7–13.8 Ma) were associated with dampening of astronomically driven climate cycles and progressive steepening of the δ 13 C gradient between intermediate and deep waters, indicating intensification and vertical expansion of ocean meridional overturning circulation following the end of the Miocene climate optimum. Together, these results underline the crucial role of the marine carbon cycle and low-latitude processes in driving climate dynamics on an almost ice-free Earth.