Eocene Thermal Maximum 2
Eocene Thermal Maximum 2 (ETM-2), also called H-1 or Elmo (Eocene Layer of Mysterious Origin), was a transient period of
The hyperthermals were geologically brief time intervals (<200,000 years) of global warming and massive input of isotopically light carbon into the ocean and atmosphere.
Timing
ETM-2 is clearly recognized in sediment sequences by analyzing the stable carbon isotope composition of carbon-bearing material.[3][9][10] The 13C/12C ratio of calcium carbonate or organic matter drops significantly across the event.[12] This is similar to what happens when one examines sediment across the PETM, although the magnitude of the negative carbon isotope excursion is not as large. The timing of Earth system perturbations during ETM-2 and PETM also appear different.[5] Specifically, the onset of ETM-2 may have been longer (perhaps 30,000 years) while the recovery seems to have been shorter (perhaps <50,000 years).[5] (Note, however, that the timing of short-term carbon cycle perturbations during both events remains difficult to constrain.)
A thin clay-rich horizon marks ETM-2 in marine sediment from widely separated locations. In sections recovered from the deep sea (for example those recovered by Ocean Drilling Program Leg 208 on Walvis Ridge), this layer is caused by dissolution of calcium carbonate.[5] However, in sections deposited along continental margins (for example those now exposed along the Waiau Toa / Clarence River, New Zealand), the clay-rich horizon represents dilution by excess accumulation of terrestrial material entering the ocean.[4] Similar changes in sediment accumulation are found across the PETM.[4] In sediment from Lomonosov Ridge in the Arctic Ocean, intervals across both ETM-2 and PETM show signs of higher temperature, lower salinity and lower dissolved oxygen.[8]
Causes
The PETM and ETM-2 are thought to have a similar generic origin,
The H-2 event appears to be a "minor" hyperthermal that follows ETM-2 (H-1) by about 100,000 years. This has led to speculation that the two events are somehow coupled and paced by changes in orbital eccentricity.[4][5]
Sea surface temperatures (SSTs) climbed by 2–4 °C and salinity by ~1–2 ppt[clarification needed] in subtropical waters during ETM-2.[13]
Effects
Ocean acidification did occur during ETM2 as it did in the PETM, but the magnitude of the drop in pH was significantly lower.[14]
As in the case of the PETM, reversible dwarfing of mammals has been noted to have occurred during the ETM-2.[15][16]
See also
References
- .
- S2CID 149669059. Retrieved 4 December 2022.
- ^ S2CID 2139892.
- ^ .
- ^ S2CID 41123449.
- PMID 18202643.
- . Retrieved 3 December 2022 – via Elsevier Science Direct.
- ^ S2CID 130137472.
- ^ S2CID 55327247.
- ^ doi:10.1038/NGEO1427.
- S2CID 130982094.
- doi:10.1130/G31585.1. Retrieved 6 April 2023.
- doi:10.1130/G39658.1. Retrieved 25 June 2023.
- ISSN 2572-4517. Retrieved 31 December 2023.
- PMID 28345031.
- ^ Erickson, J. (1 November 2013). "Global warming led to dwarfism in mammals – twice". University of Michigan. Retrieved 12 November 2013.
External links
- Appy Sluijs. "Climate and carbon cycle dynamics during late Paleocene – early Eocene transient global warming events" (PDF). Archived from the original (PDF) on 30 May 2009.
- Lucy Stap; Appy Sluijs; Ellen Thomas; Lucas Lourens. "Patterns and magnitude of deep sea carbonate dissolution during Eocene Thermal Maximum 2 and H2, Walvis Ridge, southeastern Atlantic Ocean". Archived from the original on 20 September 2012. Retrieved 18 July 2009.