Eocene Thermal Maximum 2

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The Eocene Thermal Maximum 2 ( ETM-2 ), also known as the H-1 event or Elmo event, was a transient period of global warming that occurred in warm climates about 53.7 million years ago. This appears to be the second thermal anomaly marking the long warming trend from the late Paleocene to the early Eocene (58 to 50 million years ago).

From a geological point of view, both heat anomalies expired in a short period of time (<200,000 years) and were characterized by global warming and massive carbon input into the carbon cycle . The strongest and best-studied event, the Paleocene / Eocene temperature maximum (PETM or ETM-1) occurred about 2 million years before ETM-2, i.e. about 55.5 million years ago. Further heat anomalies followed ETM-2 53.6 million years ago (H-2), 53.3 million years ago (I-1) and 52.8 million years, which are designated as K, X or ETM-3 . The number, nomenclature, absolute age and relative global effect of the Eocene heat anomalies are the subject of ongoing scientific research. In any case, the thermal anomalies appear to be the early Eocene climatic optimumHaving brought about the warmest period of the Cenozoic . They definitely took place before the Azolla event about 49 million years ago.

ETM-2 can be clearly identified in sedimentary structures by analyzing stable carbon isotopes in carbon-bearing material. The 13 C / 12 C ratio of the calcium carbonate or organic material drops significantly over the course of the event. The events are thus similar to the PETM, although the amount of the negative carbon isotope excursion is smaller. The timing of the disturbances of the earth system in the course of the ETM-2 also run differently than during the PETM. ETM-2 started for a longer period than PETM (about 30,000 years), whereas the "recovery time" was shorter (about 50,000) years. In both cases it should be considered that the duration of the processes is very difficult to reconstruct exactly.

A clay-rich layer of ETM-2 in the marine sediments is also characteristic of sites that are far apart. For samples obtained from the deep sea as part of the Ocean Drilling Program - e.g. B. Leg 208 of the whale's back - this layer was caused by the dissolution of calcium carbonates. In sections that formed on the continental margins - e.g. For example, those showing along the Clarence River - the clay-rich layers are created by the washing away of abundant soil material that has been brought into the ocean. Similar changes in sediment accumulation were found over the course of the PETM. In sediment samples taken from the Lomonosov Ridge of the Arctic Ocean , signs of higher temperatures, lower salinity and lower oxygen concentrations can be detected in both ETM-2 and PETM.

It is believed that PETM and ETM-2 had similar causes. However, research into the exact causes has so far been the subject of ongoing research. During both events, enormous amounts of 13 C-depleted carbon were released into the atmosphere and oceans. This led to a decreasing 13 C / 12 C ratio of the carbon-bearing sediments. The associated warming and the resulting change and intensification of the water cycle could have increased the erosion rate and transported larger amounts of material from the continents to the oceans. This would explain the large-scale sediment deposition on the continental slopes.

The sharp rise in atmospheric carbon dioxide concentration can only explain the temperature rise observed between one and 3.5 degrees. According to a study published in Nature in 2009, other, previously unknown causes can be assumed. The authors suggest that the potential impact of these factors should still be considered today when assessing future climate change.

The H-2 event was believed to be a minor thermal anomaly and followed ETM-2 (H-1) after approximately 100,000 years. This led to speculation that both events were linked in some way and could have been caused by changes in the eccentricity of Earth's orbit.

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Individual evidence

  1. ↑ a b Lourens, LJ, Sluijs, A .; Kroon, D .; Zachos, JC; Thomas, E .; Röhl, U .; Bowles, J .; Raffi, I .: Astronomical pacing of late Palaeocene to early Eocene global warming events . In: Nature . 435, No. 7045, 2005, pp. 1083-1087. bibcode : 2005Natur.435.1083L . doi : 10.1038 / nature03814 . PMID 15944716 .
  2. ↑ a b c d e f g Nicolo, MJ, Sluijs, A .; Kroon, D .; Zachos, JC; Thomas, E .; Röhl, U .; Bowles, J .; Raffi, I .: Multiple early Eocene hyperthermals: Their sedimentary expression on the New Zealand continental margin and in the deep sea . In: Geology . 35, No. 8, 2007, pp. 699-702. doi : 10.1130 / G23648A.1 .
  3. ↑ a b c Sluijs, A., Schouten, S .; Donders, TH; Schoon. PL; Röhl, U .; Reichart, G.-J .; Sangiorgi, F .; Kim, J.-H .; Sinninghe Damsté, JS; Brinkhuis, H .: Warm and wet conditions in the Arctic region during Eocene Thermal Maximum 2 . In: Nature Geoscience . 2, No. 11, 2009, pp. 777-780. bibcode : 2009NatGe ... 2..777S . doi : 10.1038 / ngeo668 .
  4. ↑ a b c d e f g Stap, L., Lourens, LJ; Thomas, E .; Sluijs, A .; Bohaty, S .; Zachos, JC: High-resolution deep-sea carbon and oxygen isotope records of Eocene Thermal Maximum 2 and H2 . In: Geology . 38, No. 7, 2010, pp. 607-610. doi : 10.1130 / G30777.1 .
  5. ↑ James Zachos , Richard E. Zeebe, Gerald R. Dickens: An early Cenozoic perspective on greenhouse warming and carbon-cycle dynamics . In: Nature . 451, No. 7176, 2008, pp. 279-283. bibcode : 2008Natur.451..279Z . doi : 10.1038 / nature06588 . PMID 18202643 .
  6. ^ Richard E. Zeebe, James C. Zachos, Gerald R. Dickens: Carbon dioxide forcing alone insufficient to explain Palaeocene-Eocene Thermal Maximum warming . In: Nature Geoscience 2, 2009, pp. 576-580, doi : 10.1038 / ngeo578 .