2023 Fiscal Year Research-status Report
The influence of land-surface reactivity on atmospheric carbon dioxide during past hyperthermals
| Project/Area Number |
22K14137
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| Research Institution | Japan Agency for Marine-Earth Science and Technology |
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Principal Investigator |
Sproson Adam 国立研究開発法人海洋研究開発機構, 海洋機能利用部門(生物地球化学センター), Young Research Fellow (40937728)
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | Silicate weathering / Magnesium isotopes / Lithium isotopes / Paleoclimate |
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| Outline of Annual Research Achievements |
In this study, marine sediments were analysed for magnesium and lithium isotopes to create a time-series of chemical and physical silicate weathering in the Earth’s geological past. The purpose is to elucidate the response of silicate weathering, which experts a major control on atmospheric CO2 concentration, to regional and global warming. A warmer, wetter climate should provide more energy and fluids for silicate weathering reaction at the Earth’s surface to occur, consuming atmospheric CO2 and reversing the global warming trend. However, if the products of silicate weathering remain in the surficial system for too long before being deposited in marine sediments, they are converted back to silicates (reverse weathering), remitting the consumed CO2 leading to no net change on climate.
During the past fiscal year, 200 sediment samples from several IODP cores collected from deep ocean basins as well as the Amazon margin were ordered, dried, crushed and chemically processed to extract the carbonate, iron oxide and silicate phase. Mg was purified from these phases and the Mg isotopic composition was measured by inductively coupled plasma mass spectrometry. This revealed that the carbonate and reactive phase of marine sediments could be used as a proxy for past seawater variation. Li has been purified and is awaiting measurement. This will provide records of past weathering during periods of regional and global warming over tens of thousands to millions of years to help understand the silicate weathering capacity to reverse global warming.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Marine sediments from the Amazon margin, Pacific Ocean, Indian Ocean and Atlantic Ocean were ordered and received from IODP. The samples were dried and crushed before undergoing a leaching technique to separate the carbonate, iron oxide and silicate phases. Major, minor and Rare Earth elements of these phases have been analysed successfully. Magnesium and lithium for the Pacific Ocean, Indian Ocean and Atlantic Ocean samples were purified and have undergone magnesium isotope measurement. Lithium isotopes are awaiting measurement. The Amazon samples will begin purification in the near future.
Findings from this project were presented at an international conference in France and domestic conference in Japan.
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| Strategy for Future Research Activity |
The remaining marine sediment samples from the Pacific Ocean, Indian Ocean and Atlantic Ocean will be measured for lithium isotopes soon after already being purified. The remaining ~50 Amazon River samples will undergo purification of magnesium and lithium and measurement of magnesium and lithium isotopes and element concentrations.
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| Causes of Carryover |
The global pandemic during the first fiscal year caused several aspects of the project to be delayed. Although progress was made in the subsequent fiscal year, several steps still need to be completed. Consumables such as PFA vials and tubes and high purity acids will be purchased to leach the remaining sediment samples from the Brazilian margin, purchase resins and high purity acids for the purification of magnesium and lithium from the sample matrix, and travel to Kochi for subsequent measurement of magnesium and lithium isotopes.
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