9:15 AM - 9:30 AM
[MIS08-02] Southern Ocean fronts and temperatures during MIS 11 interglacial
Keywords:MIS 11, Foraminifera
Antarctic Circumpolar Currents (ACC) consists of multiple oceanic fronts which are boundaries between different water masses (e.g., temperature and salinity). The ACC and the oceanic fronts tend to migrate southward in response to anthropogenic warming. In contrast, during Marine Isotope Stage 11 interglacial around 400 kyrs ago, global mean temperature was potentially higher by 2 degrees than preindustrial. Thus, understanding MIS 11 climate including changes in the ACC and the oceanic fronts are required. In this study, we reconstruct the Southern Ocean fronts and temperatures during MIS 11 based on planktic foraminifera.
Studied site MD19-3578 is located around the Crozet island in the Indian sector of the Southern Ocean, and is south of modern Subantarctic Front (SAF). Major lithology is diatom ooze, except for ~1.2 m calcareous ooze. Preliminary age model suggest that the calcareous ooze deposited during MIS 11.
For planktic foraminifera assemblage during MIS 11, temperate species Globigerina bulloides yielded up to 51%. However, the same species is only 26% in the coretop sediments, suggesting warmer condition during MIS 11 peak. Because G. bulloides abundance increases north of the modern SAF, during MIS 11 peak the SAF likely migrated southward.
For G. bulloides Mg/Ca ratio (temperature proxy), it ranged from 1.68 to 1.90 mmol/mol, which corresponds to 7.9 degree C to 9.8 degree C. The same species Mg/Ca-based temperature in the coretop sediments was 5.0 degree C, thus MIS 11 temperature is significantly higher than present day. In summary, during MIS 11 the SAF migrated southward in the Indian sector of the Southern Ocean, and the temperature at the studied site increased by 3 to 4 degrees than present day.
Studied site MD19-3578 is located around the Crozet island in the Indian sector of the Southern Ocean, and is south of modern Subantarctic Front (SAF). Major lithology is diatom ooze, except for ~1.2 m calcareous ooze. Preliminary age model suggest that the calcareous ooze deposited during MIS 11.
For planktic foraminifera assemblage during MIS 11, temperate species Globigerina bulloides yielded up to 51%. However, the same species is only 26% in the coretop sediments, suggesting warmer condition during MIS 11 peak. Because G. bulloides abundance increases north of the modern SAF, during MIS 11 peak the SAF likely migrated southward.
For G. bulloides Mg/Ca ratio (temperature proxy), it ranged from 1.68 to 1.90 mmol/mol, which corresponds to 7.9 degree C to 9.8 degree C. The same species Mg/Ca-based temperature in the coretop sediments was 5.0 degree C, thus MIS 11 temperature is significantly higher than present day. In summary, during MIS 11 the SAF migrated southward in the Indian sector of the Southern Ocean, and the temperature at the studied site increased by 3 to 4 degrees than present day.