Cold climate during the closest Stage 11 analog to recent Millennia |
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| Institution: | 1. Faculty of Social Sciences and Humanities, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan;2. Archaeometry Laboratory, Research Reactor Center, University of Missouri-Columbia, 1513 Research Park Dr., Columbia, MO 65211-3400, USA;3. Institute of Archaeology and Ethnography of the Siberian Branch of the Russian Academy of Science, Sakhalin State University, Sakhalin laboratory of Archaeology and Ethnography, Pogranichnaya str.70, Yzhno-Sakhalinsk, Russia;4. Kitami City Board of Education, 376 Sakaeura, Tokoro-cho, Kitami-shi, Hokkaido 093-0216, Japan;5. Tokyo Metropolitan Archaeological Center, 1-14-2 Ochiai, Tama-shi, Tokyo 206-0033, Japan;6. Department of Archaeology, Faculty of Letters, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;1. UiT The Arctic University of Norway, Department of Geology, Tromsø, Norway;2. Norwegian Polar Institute, Tromsø, Norway;3. Akvaplan-niva AS, Tromsø, Norway;4. CAGE — Centre for Arctic Gas Hydrate, Environment, and Climate, Department of Geology, UiT The Arctic University of Norway, Norway |
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| Abstract: | The early part of marine isotopic Stage 11 near 400,000 years ago provides the closest analog to Holocene insolation levels of any interglaciation during the era of strong 100,000-year climatic cycles. The CH4 concentration measured in Vostok ice fell to ～450 ppb, and CO2 values to ～250 ppm. These natural decreases contrast with the increases in recent millennia and support the early anthropogenic hypothesis of major gas emissions from late-Holocene farming. During the same interval, δD values fell from typical interglacial to nearly glacial values, indicating a major cooling in Antarctica early in Stage 11. Other evidence suggests that new ice was accumulating during the closest insolation analog to the present day: a major increase in δ18Oatm at Vostok, a similar increase in marine δ18O values, and re-initiation of ice rafting in the Nordic Sea. The evidence permits extended (>20,000 year) intervals of Stage 11 interglacial warmth in the Antarctic and North Atlantic, yet it also requires that this warmth ended and a new glacial era began when insolation was most similar to recent millennia. The Holocene CO2 anomaly was produced only in part by direct anthropogenic emissions; over half of the anomaly resulted from the failure of CO2 values to fall as they had during previous interglaciations because of natural responses, including a sea-ice advance in the Antarctic and ice-sheet growth in the northern hemisphere. |
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