Changes in the concentration of atmospheric carbon dioxide (CO2) are considered to be a major cause of climate change in the past and future. The long-running debate focuses on whether about 30 percent of the CO2 content below the ice cap is due to iron ore fertilization. Iron-rich dust is said to be carried to the sea by air and water, where it promotes the growth of algae that absorb large amounts of CO2. As algae die and sink permanently in the ocean floor, CO2 also stays there as a trap. Although there is clear evidence that dust deposits increase during the winter season, the effect of fertilization is controversial, at least in the Antarctic
Detectives from 13 countries led by Drs. Michael Weber of the Institute for Geosciences at the University of Bonn investigated this question. As part of the Integrated Marine Discovery Program (IODP), the team traveled to the Scotia Sea on a “JOIDES Resolution” exercise and spent two months in 2019 removing cores from the bottom of the sea at a depth of 3,000 to 4,000 meters. Weber: “We have collected the highest resolution weather archive ever found near Antarctica and its largest source of dust, Patagonia.”
1.5 million years of weather history
In the deep-sea core U1537 200 meters long, the weather history of 1.5 million years ago is recorded in detail. This allows for the reconstruction of dust deposits to double, as Antarctica’s ice cores cover only 800,000 years ago. Current records from the depths of the ocean indicate that dust accumulation during the snowy season was actually five to 15 times higher. This is also seen in snow camps.
However, researchers found no evidence of the effect of fertile soil on the Antarctic Ocean during the ice age. Instead, algae production, for example, as well as carbon dioxide emissions, were only high during warmer days when the pollutants in the Scottish seas were lower.
This means that in cold climates, some processes prevent CO2 taken from the oceans from escaping into the atmosphere and causing overheating. The key factors here are the widespread coverage of sea ice, the strong fragmentation of the oceans, and the reduction of current system fluctuations, which have contributed to the reduction of CO2 content in the atmosphere during cold weather.The conflicting methods of dust dissipation and ocean production during the ice and the Pleistocene period are accompanied by long-term, gradual changes in the climate system in the southern polar region. Bioproductivity was very high during the ice confluence period of 400,000 years ago, but during the Pleistocene transition 1.2 million to 700,000 years ago, it differed slightly from that in colder climates.
As the revolution progressed, dust deposits covered larger and larger areas in the Southern Hemisphere. Rapid changes continued to occur 900,000 years ago, marking the great Antarctic ice sheet.”Certainly there is evidence of the effect of fertilization during the winter on the cores outside the Antarctic region,” concludes Weber. “However, our research shows that fluctuations in CO2 emissions in the atmosphere do not depend solely on the fertilization of iron from the dust. -1.5 years ago”.
Source Journal Reference: Michael E. Weber, Ian Bailey, Sidney R. Hemming, Yasmina M. Martos, Brendan T. Reilly, Thomas A. Ronge, Stefanie Brachfeld, Trevor Williams, Maureen Raymo, Simon T. Belt, Lukas Smik, Hendrik Vogel, Victoria L. Peck, Linda Armbrecht, Alix Cage, Fabricio G. Cardillo, Zhiheng Du, Gerson Fauth, Christopher J. Fogwill, Marga Garcia, Marlo Garnsworthy, Anna Glüder, Michelle Guitard, Marcus Gutjahr, Iván Hernández-Almeida, Frida S. Hoem, Ji-Hwan Hwang, Mutsumi Iizuka, Yuji Kato, Bridget Kenlee, Suzanne OConnell, Lara F. Pérez, Osamu Seki, Lee Stevens, Lisa Tauxe, Shubham Tripathi, Jonathan Warnock, Xufeng Zheng. Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years. Nature Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-29642-5
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