A Cenozoic record of the equatorial Pacific carbonate compensation depth

• Published in: Nature (London) 2012-08, Vol.488 (7413), p.609-614
• Main Authors: Pälike, Heiko, Lyle, Mitchell W., Nishi, Hiroshi, Raffi, Isabella, Ridgwell, Andy, Gamage, Kusali, Klaus, Adam, Acton, Gary, Anderson, Louise, Backman, Jan, Baldauf, Jack, Beltran, Catherine, Bohaty, Steven M., Bown, Paul, Busch, William, Channell, Jim E. T., Chun, Cecily O. J., Delaney, Margaret, Dewangan, Pawan, Dunkley Jones, Tom, Edgar, Kirsty M., Evans, Helen, Fitch, Peter, Foster, Gavin L., Gussone, Nikolaus, Hasegawa, Hitoshi, Hathorne, Ed C., Hayashi, Hiroki, Herrle, Jens O., Holbourn, Ann, Hovan, Steve, Hyeong, Kiseong, Iijima, Koichi, Ito, Takashi, Kamikuri, Shin-ichi, Kimoto, Katsunori, Kuroda, Junichiro, Leon-Rodriguez, Lizette, Malinverno, Alberto, Moore Jr, Ted C., Murphy, Brandon H., Murphy, Daniel P., Nakamura, Hideto, Ogane, Kaoru, Ohneiser, Christian, Richter, Carl, Robinson, Rebecca, Rohling, Eelco J., Romero, Oscar, Sawada, Ken, Scher, Howie, Schneider, Leah, Sluijs, Appy, Takata, Hiroyuki, Tian, Jun, Tsujimoto, Akira, Wade, Bridget S., Westerhold, Thomas, Wilkens, Roy, Williams, Trevor, Wilson, Paul A., Yamamoto, Yuhji, Yamamoto, Shinya, Yamazaki, Toshitsugu, Zeebe, Richard E.
• Format: Article
• Language: English
• Subjects: 704/106/413; 704/2151/213; Altitude; Atmosphere - chemistry; Calcium carbonate; Calcium Carbonate - analysis; Carbon; Carbon Cycle; Carbon dioxide; Carbon Dioxide - analysis; Cenozoic; Compensation; Compensation depth; Diatoms - metabolism; Drilling; Earth sciences; Earth, ocean, space; Eocene; Exact sciences and technology; Fluctuations; Foraminifera - metabolism; Geochemical exploration, methodology, general; Geologic Sediments - chemistry; Geology; Global Warming - history; Global Warming - statistics & numerical data; History, 21st Century; History, Ancient; Humanities and Social Sciences; Marine Biology; Metallic and non-metallic deposits; multidisciplinary; Oxygen - metabolism; Pacific Ocean; Rocks; Science; Science (multidisciplinary); Sciences of the Universe; Seawater - chemistry; Stratigraphy; Temperature; Weathering
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature11360

Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0–3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth. A detailed reconstruction of the calcium carbonate compensation depth—at which calcium carbonate is dissolved—in the equatorial Pacific Ocean over the past 53 million years shows that it tracks ocean cooling, increasing as the ocean cools. A history of carbon cycles and climate change The carbonate compensation depth — the oceanic depth at which carbonate is dissolved — reflects the amount of carbon dioxide present in the atmosphere, and thus gives clues about climate on geological timescales. This paper reports a detailed reconstruction of the carbonate compensation depth in the equatorial Pacific over the past 53 million years. The compensation depth is found to track ocean cooling, deepening from 3.0–3.5 kilometres during the early Cenozoic (56–53 million years ago) to 4.6 kilometres today. Rapid fluctuations observed in the carbonate compensation depth around 46–34 million years ago could be explained, in part, by changes in weathering and in the type of organic carbon supplied to the sea floor.