Middle Miocene Climatic Optimum

The Middle Miocene Climatic Optimum (MMCO), sometimes referred to as the Middle Miocene Thermal Maximum (MMTM),^[1] was an interval of warm climate during the Miocene epoch, specifically the Burdigalian and Langhian stages.^[2]

Duration

Based on the magnetic susceptibility of Miocene sedimentary stratigraphic sequences in the Huatugou section in the Qaidam Basin, the MMCO lasted from 17.5 to 14.5 Ma; rocks deposited during this interval have a high magnetic susceptibility due to the production of supermaramagnetic and single domain magnetite amidst the warm and humid conditions at the time that define the MMCO.^[3]

Estimates derived from Mg/Ca palaeothermometry in the benthic foraminifer Oridorsalis umbonatus suggest the onset of the MMCO occurred at 16.9 Ma, peak warmth at 15.3 Ma, and the end of the MMCO at 13.8 Ma.^[4]

Climate

Global mean surface temperatures during the MMCO were approximately 18.4 °C, about 3 °C warmer than today and 4 °C warmer than preindustrial.^[5] The latitudinal zone of tropical climate was significantly greatened.^[6] During orbital eccentricity maxima, which corresponded to warm phases, the ocean's lysocline shoaled by approximately 500 metres.^[7]

The Arctic was ice free and warm enough to host permanent forest cover across much of its extent. Iceland had a humid and subtropical climate.^[2]

The mean annual temperature (MAT) of the United Kingdom was 16.9 °C.^[8] In Central Europe, the minimal cold months temperature (mCMT) was at least 8.0 °C and the minimal warm months temperature (mWMT) about 18.3 °C, with a total MAT of no cooler than 17.4 °C.^[9] Dense, humid rainforests covered much of France, Switzerland, and northern Germany, while southern and central Spain were arid and contained open environments.^[10] In the North Alpine Foreland Basin (NAFB), hydrological cycling intensified during the MMCO.^[11] The Austrian locality of Stetten had a mean winter temperature of 9.6-13.3 °C and a mean summer temperature of 24.7-27.9 °C, contrasting with -1.4 °C and 19.9 °C in the present, respectively; precipitation amounts at this site were 9–24 mm in winter and 204–236 mm in summer.^[12]

The Northern Hemisphere summer location of the Intertropical Convergence Zone (ITCZ) shifted northward; because the ITCZ is the zone of maximal monsoonal rainfall, the precipitation brought by the East Asian Summer Monsoon (EASM) increased over southern China while simultaneously declining over Indochina.^[13] The Tibetan Plateau was overall wetter and warmer.^[3]

Overall, western North America north of 40 °N was wetter than south of 40 °N.^[14] The Mojave region of western North America exhibited a drying trend.^[15] Along the New Jersey shelf, the MMCO did not result in any discernable climatic signal relative to earlier or later climatic intervals of the Miocene; temperatures here may have been kept low by an uplift of the Appalachian Mountains.^[16]

Northern South America developed increased seasonality in its precipitation patterns as a consequence of the ITCZ's northward migration during the MMCO.^[17] The Bolivian Altiplano had a MAT of 21.5-21.7 ± 2.1 °C, in stark contrast to its present MAT of 8-9 °C, while its MMCO precipitation patterns were identical to those of today.^[18]

In Antarctica, average summer temperatures were about 10 °C.^[19] The East Antarctic Ice Sheet (EAIS) was severely reduced in area.^[20][21] However, despite its diminished size and its retreat away from the coastline of Antarctica, the EAIS remained relatively thick.^[22] Additionally, Antarctica's polar ice sheets exhibited high variability and instability throughout this warm period.^[23]

Causes

The global warmth of the MMCO resulted from its elevated atmospheric carbon dioxide concentrations relative to the rest of the Neogene.^[2] Boron-based records indicate pCO₂ varied between 300 and 500 ppm during the MMCO.^[23] A MMCO pCO₂ estimate of 852 ± 86 ppm has been derived from palaeosols in Railroad Canyon, Idaho.^[24] The primary cause of this high pCO₂ is generally accepted to be elevated volcanic activity.^[25][26] Hydrothermal alteration by magmatic dikes and sills of sediments rich in organic carbon further contributed to rising pCO₂.^[27] The activity of the Columbia River Basalt Group (CRBG), a large igneous province in the northwestern United States that emitted 95% of its contents between 16.7 and 15.9 Ma, is believed to be the dominant geological event responsible for the MMCO.^[28] The CRBG has been estimated to have added 4090–5670 Pg of carbon into the atmosphere in total, 3000-4000 Pg of which was discharged during the Grande Ronde Basalt eruptions, explaining much of the MMCO's anomalous warmth. Carbon dioxide was released both directly from volcanic activity as well as cryptic degassing from intrusive magmatic sills that liberated the greenhouse gas from existing sediments. However, CRBG activity and cryptic degassing does not sufficiently explain warming before 16.3 Ma.^[29] Enhanced tectonic activity led to increased volcanic degassing at plate margins, enabling high background warmth to occur and complementing CRBG activity in driving temperatures upwards.^[30]

Albedo decrease from the reduction in Earth's surface area covered by deserts and the expansion of forests was an important positive feedback enhancing the warmth of the MMCO.^[31]

The increase in organic carbon burial on lands submerged by rising sea levels resultant from the increased warmth were an important negative feedback inhibiting further warming.^[32][33] This positive carbon excursion is called the Monterey Carbon Excursion, which is globally recorded but mainly in the circum pacific belt.^{[34][35][36][37]} The Monterey Excursion seems to envelop the MMCO, meaning this carbon excursion started just before the climatic optimum and it ended just after it.

Climate modelling has shown that there remain as-of-yet unknown forcing and feedback mechanisms that had to have existed to account for the observed rise in temperature during the MMCO,^[38] as the amount of carbon dioxide known to have been in the atmosphere during the MMCO along with other known boundary conditions are insufficient in explaining the high temperatures of the Middle Miocene.^[2]

Biotic effects

The world of the MMCO was heavily forested; trees grew across the Arctic and even in parts of Antarctica.^[2] Tundras and forest tundras were absent from the Arctic.^[39]

Northern North America was dominated by cool-temperate forests. Western North America was mostly composed of warm-temperate evergeen broadleaf and mixed forest.^[14] In spite of the climatic changes, the niches of Oregonian equids were unchanged throughout the MMCO.^[40] What is now the Mojave Desert was a grassland dominated by C₃ grasses during the MMCO.^[15] Central America was tropical, as it is today.^[14]

In Europe, the MMCO witnessed the northward expansion of thermophilic plants.^[9] Along the northwestern coast of the Central Paratethys, mixed mesophytic forest vegetation predominated.^[41] At the Stetten locality, spruces and firs increased in abundance during transgressive phases of precessionally forced transgressive-regressive cycles, while marshes, many of them saline, dominated by Cyperaceae and swamps dominated by Taxodiaceae prevailed during sea level lowstands.^[12] Because of the dense, humid forests covering central eastern France and northern Germany, the species richness of these areas was high and the mammal community dominated by small taxa, while the more arid Iberian Peninsula had a lower species richness and a relative absence of medium-sized mammals.^[10] Europe also contained an abundance of ectothermic vertebrates due to its much warmer climate in the MMCO compared to the present.^[9]

Northern South America possessed tropical evergreen broadleaf forests. The Atacama Desert already existed along the western coast of central South America and graded into temperate xerophytic shrubland and temperate sclerophyll woodland and shrubland to the south. In eastern South America south of 35 °S, warm-temperate evergreen broadleaf and mixed forest predominated, alongside temperate grassland.^[14] The MMCO played a major role in the partitioning and diversification of South America's land mammal faunas.^[42]

Comparison to present global warming

The MMCO's temperature estimates of 3-4 °C above the preindustrial mean are similar to those projected in the future by mid-range forecasts of anthropogenic global warming conducted by the Intergovernmental Panel on Climate Change (IPCC).^[43] Estimates of future pCO₂ are also remarkably similar to those derived for the MMCO.^[2] Because of these many similarities, many palaeoclimatologists use the MMCO as an analogue for what Earth's future climate will look like.^[1] Arguably, it is the best of all possible analogues; the pCO₂ of the cooler Pliocene has already been exceeded, while the warmer Eocene had global temperatures and carbon dioxide levels so high that reaching them would require scenarios that are no longer considered realistic or likely to occur.^[2]

See also

• Palaeocene-Eocene Thermal Maximum
• Early Eocene Climatic Optimum
• Middle Eocene Climatic Optimum

References

1. Scotese, Christopher R.; Song, Haijun; Mills, Benjamin J.W.; van der Meer, Douwe G. (1 April 2021). "Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years". Earth-Science Reviews. 215: 103503. Bibcode:2021ESRv..21503503S. doi:10.1016/j.earscirev.2021.103503. S2CID 233579194. Retrieved 24 December 2023.
2. Steinthorsdottir, M.; Coxall, H. K.; de Boer, A. M.; Huber, M.; Barbolini, N.; Bradshaw, C. D.; Burls, N. J.; Feakins, S. J.; Gasson, E.; Henderiks, J.; Holbourn, A. E.; Kiel, S.; Kohn, M. J.; Knorr, G.; Kürschner, W. M. (23 December 2020). "The Miocene: The Future of the Past". Paleoceanography and Paleoclimatology. 36 (4). doi:10.1029/2020PA004037. ISSN 2572-4517. Retrieved 24 December 2023 – via Wiley Online Library.
3. Guan, Chong; Chang, Hong; Yan, Maodu; Li, Leyi; Xia, Mengmeng; Zan, Jinbo; Liu, Shuangchi (15 October 2019). "Rock magnetic constraints for the Mid-Miocene Climatic Optimum from a high-resolution sedimentary sequence of the northwestern Qaidam Basin, NE Tibetan Plateau". Palaeogeography, Palaeoclimatology, Palaeoecology. 532: 109263. Bibcode:2019PPP...53209263G. doi:10.1016/j.palaeo.2019.109263. ISSN 0031-0182. S2CID 198407262. Retrieved 10 January 2024 – via Elsevier Science Direct.
4. Kochhann, Karlos G. D.; Holbourn, Ann; Kuhnt, Wolfgang; Xu, Jian (1 May 2017). "Eastern equatorial Pacific benthic foraminiferal distribution and deep water temperature changes during the early to middle Miocene". Marine Micropaleontology. 133: 28–39. Bibcode:2017MarMP.133...28K. doi:10.1016/j.marmicro.2017.05.002. ISSN 0377-8398. Retrieved 10 January 2024 – via Elsevier Science Direct.
5. You, Y.; Huber, M.; Müller, R. D.; Poulsen, C. J.; Ribbe, J. (19 February 2009). "Simulation of the Middle Miocene Climate Optimum". Geophysical Research Letters. 36 (4). Bibcode:2009GeoRL..36.4702Y. doi:10.1029/2008GL036571. ISSN 0094-8276. Retrieved 24 December 2023 – via Wiley Online Library.
6. Kroh, Andreas (14 September 2007). "Climate changes in the Early to Middle Miocene of the Central Paratethys and the origin of its echinoderm fauna". Palaeogeography, Palaeoclimatology, Palaeoecology. Miocene Climate in Europe - patterns and evolution. First synthesis of NECLIME. 253 (1): 169–207. Bibcode:2007PPP...253..169K. doi:10.1016/j.palaeo.2007.03.039. ISSN 0031-0182. Retrieved 24 December 2023 – via Elsevier Science Direct.
7. Kochhann, Karlos G. D.; Holbourn, Ann; Kuhnt, Wolfgang; Channell, James E. T.; Lyle, Mitch; Shackford, Julia K.; Wilkens, Roy H.; Andersen, Nils (22 August 2016). "Eccentricity pacing of eastern equatorial Pacific carbonate dissolution cycles during the Miocene Climatic Optimum: ECCENTRICITY-PACED DISSOLUTION CYCLES". Paleoceanography and Paleoclimatology. 31 (9): 1176–1192. doi:10.1002/2016PA002988. Retrieved 4 September 2023.
8. Gibson, M. E.; McCoy, J.; O’Keefe, J. M. K.; Nuñez Otaño, N. B.; Warny, S.; Pound, M. J. (12 January 2022). "Reconstructing Terrestrial Paleoclimates: A Comparison of the Co-Existence Approach, Bayesian and Probability Reconstruction Techniques Using the UK Neogene". Paleoceanography and Paleoclimatology. 37 (2). Bibcode:2022PaPa...37.4358G. doi:10.1029/2021PA004358. ISSN 2572-4517. Retrieved 30 December 2023.
9. Böhme, Madelaine (15 June 2003). "The Miocene Climatic Optimum: evidence from ectothermic vertebrates of Central Europe". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (3): 389–401. Bibcode:2003PPP...195..389B. doi:10.1016/S0031-0182(03)00367-5. ISSN 0031-0182. Retrieved 30 December 2023 – via Elsevier Science Direct.
10. Costeur, L.; Legendre, S. (1 May 2008). "Mammalian Communities Document a Latitudinal Environmental Gradient during the Miocene Climatic Optimum in Western Europe". PALAIOS. 23 (5): 280–288. Bibcode:2008Palai..23..280C. doi:10.2110/palo.2006.p06-092r. ISSN 0883-1351. S2CID 131185516. Retrieved 30 December 2023.
11. Methner, Katharina; Campani, Marion; Fiebig, Jens; Löffler, Niklas; Kempf, Oliver; Mulch, Andreas (14 May 2020). "Middle Miocene long-term continental temperature change in and out of pace with marine climate records". Scientific Reports. 10 (1): 7989. Bibcode:2020NatSR..10.7989M. doi:10.1038/s41598-020-64743-5. ISSN 2045-2322. PMC 7224295. PMID 32409728.
12. Kern, Andrea; Harzhauser, Mathias; Mandic, Oleg; Roetzel, Reinhard; Ćorić, Stjepan; Bruch, Angela A.; Zuschin, Martin (1 May 2011). "Millennial-scale vegetation dynamics in an estuary at the onset of the Miocene Climate Optimum". Palaeogeography, Palaeoclimatology, Palaeoecology. The Neogene of Eurasia: Spatial gradients and temporal trends - The second synthesis of NECLIME. 304 (3): 247–261. Bibcode:2011PPP...304..247K. doi:10.1016/j.palaeo.2010.07.014. ISSN 0031-0182. PMC 3196839. PMID 22021937.
13. Liu, Chang; Clift, Peter D.; Giosan, Liviu; Miao, Yunfa; Warny, Sophie; Wan, Shiming (1 July 2019). "Paleoclimatic evolution of the SW and NE South China Sea and its relationship with spectral reflectance data over various age scales". Palaeogeography, Palaeoclimatology, Palaeoecology. 525: 25–43. Bibcode:2019PPP...525...25L. doi:10.1016/j.palaeo.2019.02.019. S2CID 135413974. Retrieved 14 November 2022.
14. Pound, Matthew J.; Haywood, Alan M.; Salzmann, Ulrich; Riding, James B. (1 April 2012). "Global vegetation dynamics and latitudinal temperature gradients during the Mid to Late Miocene (15.97–5.33Ma)". Earth-Science Reviews. 112 (1): 1–22. Bibcode:2012ESRv..112....1P. doi:10.1016/j.earscirev.2012.02.005. ISSN 0012-8252. Retrieved 10 January 2024 – via Elsevier Science Direct.
15. Smiley, Tara M.; Hyland, Ethan G.; Cotton, Jennifer M.; Reynolds, Robert E. (15 January 2018). "Evidence of early C4 grasses, habitat heterogeneity, and faunal response during the Miocene Climatic Optimum in the Mojave Region". Palaeogeography, Palaeoclimatology, Palaeoecology. 490: 415–430. Bibcode:2018PPP...490..415S. doi:10.1016/j.palaeo.2017.11.020. ISSN 0031-0182. Retrieved 10 January 2024 – via Elsevier Science Direct.
16. Kotthoff, U.; Greenwood, D. R.; McCarthy, F. M. G.; Müller-Navarra, K.; Prader, S.; Hesselbo, S. P. (25 August 2014). "Late Eocene to middle Miocene (33 to 13 million years ago) vegetation and climate development on the North American Atlantic Coastal Plain (IODP Expedition 313, Site M0027)". Climate of the Past. 10 (4): 1523–1539. Bibcode:2014CliPa..10.1523K. doi:10.5194/cp-10-1523-2014. ISSN 1814-9332. Retrieved 10 January 2024.
17. Scholz, Serena R.; Petersen, Sierra V.; Escobar, Jaime; Jaramillo, Carlos; Hendy, Austin J.W.; Allmon, Warren D.; Curtis, Jason H.; Anderson, Brendan M.; Hoyos, Natalia; Restrepo, Juan C.; Perez, Nicolas (1 July 2020). "Isotope sclerochronology indicates enhanced seasonal precipitation in northern South America (Colombia) during the Mid-Miocene Climatic Optimum". Geology. 48 (7): 668–672. Bibcode:2020Geo....48..668S. doi:10.1130/G47235.1. ISSN 0091-7613. Retrieved 10 January 2024.
18. Gregory-Wodzicki, Kathryn M.; McIntosh, W. C.; Velasquez, Kattia (1 December 1998). "Climatic and tectonic implications of the late Miocene Jakokkota flora, Bolivian Altiplano". Journal of South American Earth Sciences. 11 (6): 533–560. Bibcode:1998JSAES..11..533G. doi:10.1016/S0895-9811(98)00031-5. ISSN 0895-9811. Retrieved 10 January 2024 – via Elsevier Science Direct.
19. Warny, Sophie; Askin, Rosemary A.; Hannah, Michael J.; Mohr, Barbara A.R.; Raine, J. Ian; Harwood, David M.; Florindo, Fabio; the SMS Science Team (1 October 2009). "Palynomorphs from a sediment core reveal a sudden remarkably warm Antarctica during the middle Miocene". Geology. 37 (10): 955–958. Bibcode:2009Geo....37..955W. doi:10.1130/G30139A.1. ISSN 1943-2682. Retrieved 4 September 2023.
20. Gasson, Edward; DeConto, Robert M.; Pollard, David; Levy, Richard H. (29 March 2016). "Dynamic Antarctic ice sheet during the early to mid-Miocene". Proceedings of the National Academy of Sciences of the United States of America. 113 (13): 3459–3464. Bibcode:2016PNAS..113.3459G. doi:10.1073/pnas.1516130113. ISSN 0027-8424. PMC 4822592. PMID 26903645.
21. Levy, Richard; Harwood, David; Florindo, Fabio; Sangiorgi, Francesca; Tripati, Robert; von Eynatten, Hilmar; Gasson, Edward; Kuhn, Gerhard; Tripati, Aradhna; DeConto, Robert; Fielding, Christopher; Field, Brad; Golledge, Nicholas; McKay, Robert; Naish, Timothy (29 March 2016). "Antarctic ice sheet sensitivity to atmospheric CO 2 variations in the early to mid-Miocene". Proceedings of the National Academy of Sciences of the United States of America. 113 (13): 3453–3458. Bibcode:2016PNAS..113.3453L. doi:10.1073/pnas.1516030113. ISSN 0027-8424. PMC 4822588. PMID 26903644.
22. Halberstadt, Anna Ruth W.; Chorley, Hannah; Levy, Richard H.; Naish, Timothy; DeConto, Robert M.; Gasson, Edward; Kowalewski, Douglas E. (15 June 2021). "CO2 and tectonic controls on Antarctic climate and ice-sheet evolution in the mid-Miocene". Earth and Planetary Science Letters. 564: 116908. doi:10.1016/j.epsl.2021.116908. ISSN 0012-821X. Retrieved 24 December 2023 – via Elsevier Science Direct.
23. Greenop, Rosanna; Foster, Gavin L.; Wilson, Paul A.; Lear, Caroline H. (11 August 2014). "Middle Miocene climate instability associated with high-amplitude CO 2 variability". Paleoceanography and Paleoclimatology. 29 (9): 845–853. doi:10.1002/2014PA002653. ISSN 0883-8305. Retrieved 30 December 2023.
24. Retallack, Gregory J. (1 October 2009). "Refining a pedogenic-carbonate CO2 paleobarometer to quantify a middle Miocene greenhouse spike". Palaeogeography, Palaeoclimatology, Palaeoecology. 281 (1): 57–65. Bibcode:2009PPP...281...57R. doi:10.1016/j.palaeo.2009.07.011. ISSN 0031-0182. Retrieved 30 December 2023 – via Elsevier Science Direct.
25. Goto, Kosuke T.; Tejada, Maria Luisa G.; Tajika, Eiichi; Suzuki, Katsuhiko (26 January 2023). "Enhanced magmatism played a dominant role in triggering the Miocene Climatic Optimum". Communications Earth & Environment. 4 (1): 21. Bibcode:2023ComEE...4...21G. doi:10.1038/s43247-023-00684-x. ISSN 2662-4435. Retrieved 24 December 2023.
26. Holbourn, Ann; Kuhnt, Wolfgang; Kochhann, Karlos G.D.; Andersen, Nils; Sebastian Meier, K.J. (1 February 2015). "Global perturbation of the carbon cycle at the onset of the Miocene Climatic Optimum". Geology. 43 (2): 123–126. Bibcode:2015Geo....43..123H. doi:10.1130/G36317.1. ISSN 1943-2682.
27. Bindeman, I. N.; Greber, N. D.; Melnik, O. E.; Artyomova, A. S.; Utkin, I. S.; Karlstrom, L.; Colón, D. P. (23 June 2020). "Pervasive Hydrothermal Events Associated with Large Igneous Provinces Documented by the Columbia River Basaltic Province". Scientific Reports. 10 (1): 10206. Bibcode:2020NatSR..1010206B. doi:10.1038/s41598-020-67226-9. ISSN 2045-2322. PMC 7311473. PMID 32576933.
28. Kasbohm, Jennifer; Schoene, Blair (7 September 2018). "Rapid eruption of the Columbia River flood basalt and correlation with the mid-Miocene climate optimum". Science Advances. 4 (9): eaat8223. Bibcode:2018SciA....4.8223K. doi:10.1126/sciadv.aat8223. ISSN 2375-2548. PMC 6154988. PMID 30255148.
29. Armstrong MKay, David I.; Tyrrell, Toby; Wilson, Paul A.; Foster, Gavin L. (1 October 2014). "Estimating the impact of the cryptic degassing of Large Igneous Provinces: A mid-Miocene case-study". Earth and Planetary Science Letters. 403: 254–262. Bibcode:2014E&PSL.403..254A. doi:10.1016/j.epsl.2014.06.040. ISSN 0012-821X. Retrieved 24 December 2023.
30. Longman, Jack; Mills, Benjamin J. W.; Donnadieu, Yannick; Goddéris, Yves (28 January 2022). "Assessing Volcanic Controls on Miocene Climate Change". Geophysical Research Letters. 49 (2). Bibcode:2022GeoRL..4996519L. doi:10.1029/2021GL096519. ISSN 0094-8276. S2CID 245863119. Retrieved 24 December 2023.
31. Henrot, A.-J.; François, L.; Favre, E.; Butzin, M.; Ouberdous, M.; Munhoven, G. (21 October 2010). "Effects of CO², continental distribution, topography and vegetation changes on the climate at the Middle Miocene: a model study". Climate of the Past. 6 (5): 675–694. Bibcode:2010CliPa...6..675H. doi:10.5194/cp-6-675-2010. ISSN 1814-9332. Retrieved 24 December 2023.
32. Holbourn, Ann; Kuhnt, Wolfgang; Schulz, Michael; Flores, José-Abel; Andersen, Nils (September 2007). "Orbitally-paced climate evolution during the middle Miocene "Monterey" carbon-isotope excursion". Earth and Planetary Science Letters. 261 (3–4): 534–550. Bibcode:2007E&PSL.261..534H. doi:10.1016/j.epsl.2007.07.026. ISSN 0012-821X.
33. Sosdian, S. M.; Babila, T. L.; Greenop, R.; Foster, G. L.; Lear, C. H. (2020-01-09). "Ocean Carbon Storage across the middle Miocene: a new interpretation for the Monterey Event". Nature Communications. 11 (1): 134. Bibcode:2020NatCo..11..134S. doi:10.1038/s41467-019-13792-0. ISSN 2041-1723. PMC 6952451. PMID 31919344.
34. Vincent, Edith; Berger, Wolfgang H. (2013-03-18), Sundquist, E.T.; Broecker, W.S. (eds.), "Carbon Dioxide and Polar Cooling in the Miocene: The Monterey Hypothesis", Geophysical Monograph Series, Washington, D. C.: American Geophysical Union, pp. 455–468, doi:10.1029/gm032p0455, ISBN 978-1-118-66432-2, retrieved 2024-03-14
35. Banerjee, Barnita; Ahmad, Syed Masood; Raza, Waseem; Raza, Tabish (January 2017). "Paleoceanographic changes in the Northeast Indian Ocean during middle Miocene inferred from carbon and oxygen isotopes of foraminiferal fossil shells". Palaeogeography, Palaeoclimatology, Palaeoecology. 466: 166–173. Bibcode:2017PPP...466..166B. doi:10.1016/j.palaeo.2016.11.021.
36. Brandano, Marco; Cornacchia, Irene; Raffi, Isabella; Tomassetti, Laura; Agostini, Samuele (January 2017). Hesselbo, Stephen (ed.). "The Monterey Event within the Central Mediterranean area: The shallow-water record". Sedimentology. 64 (1): 286–310. doi:10.1111/sed.12348. ISSN 0037-0746.
37. Carolin, Nora; Vadlamani, Ravikant; Bajpai, Sunil (2022-06-27). "Sr isotope numerical depositional age of Miocene marine strata (Quilon Formation), Kerala–Konkan Basin, India". Journal of Earth System Science. 131 (3): 152. Bibcode:2022JESS..131..152C. doi:10.1007/s12040-022-01898-x. ISSN 0973-774X.
38. Goldner, A.; Herold, N.; Huber, M. (13 March 2014). "The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1". Climate of the Past. 10 (2): 523–536. Bibcode:2014CliPa..10..523G. doi:10.5194/cp-10-523-2014. ISSN 1814-9332. Retrieved 24 December 2023.
39. Frigola, Amanda; Prange, Matthias; Schulz, Michael (24 April 2018). "Boundary conditions for the Middle Miocene Climate Transition (MMCT v1.0)". Geoscientific Model Development. 11 (4): 1607–1626. Bibcode:2018GMD....11.1607F. doi:10.5194/gmd-11-1607-2018. ISSN 1991-9603. Retrieved 10 January 2024.
40. Maguire, Kaitlin Clare (15 May 2015). "Dietary niche stability of equids across the mid-Miocene Climatic Optimum in Oregon, USA". Palaeogeography, Palaeoclimatology, Palaeoecology. 426: 297–307. Bibcode:2015PPP...426..297M. doi:10.1016/j.palaeo.2015.03.012. ISSN 0031-0182. Retrieved 10 January 2024 – via Elsevier Science Direct.
41. Doláková, Nela; Kováčová, Marianna; Utescher, Torsten (13 December 2020). "Vegetation and climate changes during the Miocene climatic optimum and Miocene climatic transition in the northwestern part of Central Paratethys". Geological Journal. 56 (2): 729–743. doi:10.1002/gj.4056. ISSN 0072-1050. S2CID 230573901. Retrieved 24 December 2023.
42. Croft, Darin A.; Carlini, Alfredo A.; Ciancio, MartÍn R.; Brandoni, Diego; Drew, Nicholas E.; Engelman, Russell K.; Anaya, Federico (2 September 2016). "New mammal faunal data from Cerdas, Bolivia, a middle-latitude Neotropical site that chronicles the end of the Middle Miocene Climatic Optimum in South America". Journal of Vertebrate Paleontology. 36 (5): e1163574. Bibcode:2016JVPal..36E3574C. doi:10.1080/02724634.2016.1163574. ISSN 0272-4634. S2CID 87802865. Retrieved 10 January 2024 – via Taylor and Francis.
43. You, Y. (17 February 2010). "Climate-model evaluation of the contribution of sea-surface temperature and carbon dioxide to the Middle Miocene Climate Optimum as a possible analogue of future climate change". Australian Journal of Earth Sciences. 57 (2): 207–219. Bibcode:2010AuJES..57..207Y. doi:10.1080/08120090903521671. ISSN 0812-0099. S2CID 129238665. Retrieved 30 December 2023 – via Taylor and Francis.