Widespread forests once played a significant role in warming the climate during the Middle Miocene Climate Optimum (MMCO), while open Panama and Tethys Seaways served as “shortcuts” for the Atlantic Meridional Overturning Circulation (AMOC).
Scientists from the Institute of Atmospheric Physics and the Institute of Tibetan Plateau Research, both affiliated with the Chinese Academy of Sciences, have provided insights into the complex relationship between forests, ocean circulation, and climate during MMCO. They have meticulously pieced together this captivating puzzle, unveiling the profound connections among these factors. The study was published in Palaeogeography, Palaeoclimatology, Palaeoecology on March 15.
The MMCO, approximately 16.9–14.7 million years ago, was a period characterized by extensive forest coverage on land, with the exception of Antarctica. The researchers studied the climate dynamics during the MMCO by simulating ocean circulation using a coupled model called the Flexible Global Ocean-Atmosphere-Land System Model Grid-Point Version 3 (FGOALS-g3).
Although some proxy data suggested that CO2 concentrations during the MMCO were as high as those projected for the end of the 21st century, the CO2 level used in the MMCO simulation was similar to today’s. The results indicated that global average temperature in MMCO was more than 3℃ higher than at present, with forests playing a more significant role in climate regulation than previously thought. Land temperatures were particularly high in the Sahara and high northern latitudes, which are now covered by deserts and low-growing vegetation but were forested during the MMCO.
In addition to extensive forest coverage, the MMCO featured open Panama and Tethys Seaways, which differs from today’s land-sea distribution. The simulation revealed that high-salinity throughflow from the Tethys Seaway combined with fresh throughflow from the Panama Seaway in the western North Atlantic. This finding suggests that the Tethys Seaway compensated for the Panama Seaway’s contribution to the AMOC.
“By delving into the depths of our planet’s past, we can better comprehend the potential impacts of climate change on our fragile world,” said Prof. Liu Hailong, corresponding author of the study.
More information: Jilin Wei et al, Simulation of the climate and ocean circulations in the Middle Miocene Climate Optimum by a coupled model FGOALS-g3, Palaeogeography, Palaeoclimatology, Palaeoecology (2023). DOI: 10.1016/j.palaeo.2023.111509
Journal information: Palaeogeography, Palaeoclimatology, Palaeoecology.
Provided by Chinese Academy of Sciences.