New research finds that the growth of the Antarctic ice sheet was critical in triggering longer, more intense glacial cycles in the mid-Pleistocene, reshaping our understanding of global climate dynamics. The latest collaborative research led by Professor An Zhisheng from the Institute of Earth Environment of the Chinese Academy of Sciences highlights the key role of the growth of the Antarctic ice sheet and the expansion of southern hemisphere sea ice in triggering the Mid-Pleistocene Climate Transition (MPT). The study also shows how the uneven development of polar ice caps affects global climate.
MPT refers to the transformation of the Earth's climate system between about 1.25 million and 0.7 million years ago, marking a shift to a more obvious and regular glacial-interglacial cycle.
This study provides insight into the rapid expansion of the Northern Hemisphere ice sheets since the mid-Pleistocene, while also questioning many assumptions about the origin of MPT and the mechanisms behind it.
The research results were published in the latest issue of the journal Science, titled "Mid-Pleistocene climate transition triggered by Antarctic ice sheet growth."
Due to the importance of MPT to the dynamic evolution of Earth's ice sheets over the past approximately 1.25 million years, such hypotheses have been regularly debated and discussed in the journals Nature and Science over the past few decades.
Professor An Zhisheng, an academician of the Chinese Academy of Sciences and a foreign academician of the US National Academy of Sciences, said: "This study helps us understand what causes glaciations. It also illustrates how various processes in the Earth system determine and change the characteristics, dynamics and length of glacial-interglacial cycles."
This study combines geological records with numerical climate simulations to reveal the history of the asymmetric evolution of ice sheets in both hemispheres and the associated responses of the Earth's climate system.
The results show that 21.25 million years ago, the continued growth of the Antarctic ice sheet and the associated expansion of southern hemisphere sea ice triggered a decrease in temperature and an increase in water vapor in the northern hemisphere by changing the cross-equatorial pressure gradient and meridional overturning circulation. These changes promoted the development of the Arctic ice sheet and ultimately caused the Earth's glacial cycle to shift from ~40,000 years to ~100,000 years.
By studying changes in ice volume in both hemispheres, this work highlights the profound impact that the asymmetric evolution of polar ice caps has on global climate, particularly in the Northern Hemisphere.
Dr. Cai Wenju, an academician of the Australian Academy of Science, said: "This study found that this asymmetry may trigger a strong positive feedback, thereby inducing huge changes in the earth's climate. This has not been recognized before until now. This is of great significance for understanding and predicting the earth's climate under the greenhouse effect." He pointed out that this study is an example of Chinese scientists taking the lead in solving global issues in cutting-edge science.
It is urgent to quantitatively assess the link between asymmetric bihemispheric ice sheet melting and global climate change. An Zhisheng believes that doing so can improve our ability to "predict future climate change and the Earth system's response to changes in polar ice caps."
Compiled from /ScitechDaily