15:30 〜 15:45
[MIS12-26] Intermediate Water Dynamics and their Influence on the CO2 Anomalies during the Mid-Brunhes Event
キーワード：Mode Waters, Antarctic Intermediate Water, Mid-Brunhes event, Planktic Foraminifera, Mg/Ca, Clumped isotopes
Approximately 440,000 years ago, the Mid-Brunhes Event (MBE) marked a distinct transition to elevated atmospheric CO2 levels with increased amplitude between glacial and interglacial periods. Traditionally, this shift has been attributed to changes in Antarctic Bottom Water (AABW) formation. However, our research suggests that Antarctic Intermediate Water (AAIW) within the South Pacific may have played a critical role in these climatic changes.
Our 600,000-year record of mode water characteristics associated with the AAIW, derived from Mg/Ca ratios, clumped isotopes, and stable isotope analysis of planktic foraminifera, indicates a notable increase in temperature and salinity of the mid-latitude South Pacific thermocline concurrent with the MBE. Prior to the MBE, reduced salinities are attributed to iceberg-derived freshwater input, intensified by the instability of the Antarctic ice shelf. These conditions likely led to the intensified formation of AAIW mode waters, which, coupled with a decline in seawater temperature, appears to have strengthened the CO2 absorption capacity preceding the MBE.
Our findings underline the need to reassess the role of intermediate waters in modulating past atmospheric CO2 levels. Given their dynamic response to cryospheric changes, intermediate waters are crucial in Earth's climate regulation and must be accurately represented in climate models. This inclusion is vital for a thorough comprehension of the CO2 sequestration mechanisms during pivotal climatic episodes such as the MBE.
Our 600,000-year record of mode water characteristics associated with the AAIW, derived from Mg/Ca ratios, clumped isotopes, and stable isotope analysis of planktic foraminifera, indicates a notable increase in temperature and salinity of the mid-latitude South Pacific thermocline concurrent with the MBE. Prior to the MBE, reduced salinities are attributed to iceberg-derived freshwater input, intensified by the instability of the Antarctic ice shelf. These conditions likely led to the intensified formation of AAIW mode waters, which, coupled with a decline in seawater temperature, appears to have strengthened the CO2 absorption capacity preceding the MBE.
Our findings underline the need to reassess the role of intermediate waters in modulating past atmospheric CO2 levels. Given their dynamic response to cryospheric changes, intermediate waters are crucial in Earth's climate regulation and must be accurately represented in climate models. This inclusion is vital for a thorough comprehension of the CO2 sequestration mechanisms during pivotal climatic episodes such as the MBE.