The Centre for Marine Magnetism (CM²) team from the Department of Marine Science and Engineering of Southern University of Science and Technology reveals a role of land-ocean interactions in stepwise Northern Hemisphere Glaciation. The paper titled as “Role of land of interactions in stepwise Northern Hemisphere Glaciation” was published in “Nature Communications”, a leading Nature Series journal in the field of Earth Sciences.

In the last few tens of millions of years (Ma), the Earth first formed an ice sheet in Antarctic at 33 Ma. In the last few million years, the Northern Hemisphere ice sheet has been expanding. In recent decades, due to the global warming, ice sheet retreat and sea ice melt have occurred in the Arctic region, which has a significant impact on the global climate environment. It is critical and urgent to study the establishment mechanism and evolution process of the Arctic ice sheet for understanding global climate system and predicting of future climate change.

Previous studies have suggested that the establishment and expansion process of the Arctic ice sheet mainly involve the influence of atmospheric CO2 decline, the weakening of water mass ventilation in the polar regions, ocean strait closure. However, there has been a lack of understanding of the role of ocean-land interaction in the Earth’s climate system and feedback mechanism. In order to clarify the ocean-land coupling coupling process, the marine sediments of the North Pacific Ocean contain abundant information about the dust source region of East Asia and Central Asia and dynamic process of the westerlies. Previous studies have shown that enhanced dust deposition in the North Pacific is associated with the formation of permanent ice sheets in the 2.74~2.72 Ma, but the entire process of the formation and expansion of the Northern Hemisphere ice sheet remain unknown. To address this puzzle, we propose the role of ocean-land feedback processes in the Earth’s climate system and new feedback mechanism for the formation and expansion of ice sheets in the Northern Hemisphere.

In these years, our team has carried out a lot of work in the North Pacific chronology, establishment of new indicator of dust, and the application of the formation mechanism and dynamic processes of dust in the North Pacific on different timescales. Through the reconstruction of high-resolution records from ODP 1208 sediment during ODP 198. A multi-stage evolution model of ocean-land coupling in the formation and expansion of ice sheets in the Northern Hemisphere is proposed through the terrestrial vegetation and atmospheric circulation. In summary, there are three important innovations in this work: (1) it is pointed out that enhancement time of Pliocene eolian dust flux should be earlier than 2.75 million years ago, starting from the Pliocene glacial M2 stage (3.3 million years ago); (2) Describe the ocean-atmosphere interaction process in the Northern Hemisphere during the formation and expansion of the Northern Hemisphere ice sheet; (3) It further supports that the enhancement of meridional temperature gradient caused by the northern Hemisphere ice sheet is the main factor of the enhancement of the westerlies. Moreover, our study further emphasizes that the land-ocean coupling process during the global atmospheric circulation intensified the transformation of global terrestrial vegetation types, which may directly lead to the transformation of the global carbon reservoir and further trigger the global cooling.

 In the context of future global warming, due to the effect of polar amplification, the high latitudes in the northern Hemisphere will warmer than the low latitudes. This will lead to melting of the Greenland ice sheet, making the Atlantic meridional overturning continue to weaken or even sluggish. Therefore, a comprehensive understand of the feedback mechanism of different layers in the climate system could provide important references for future climate changes and model simulation.