An 80 kyr record of intermediate-depth water flow on the western South Atlantic margin

Understanding the Antarctic Intermediate Water transport is fundamental to knowing the Atlantic Meridional Overturning Circulation and its variations over time. This study investigates the temporal variations of the northward flow of the Intermediate Western Boundary Current (the leading carrier of the Antarctic Intermediate Water) over the last 80 kyr by using grain-size data (sortable silt and end-member analysis). The results presented show abrupt changes in Sortable Silt (interpreted as changes in flow speed) in the transition between Marine Isotope Stage 4 and Marine Isotope Stage 3 and during Marine Isotope Stage 3. In addition, there is a clear coarsening of Sortable Silt from the Deglacial to the Holocene, indicating an intensification of the northward transport of the Antarctic Intermediate Water along the south-western Atlantic margin. These results highlight the existence of a prevailing positive relationship between the northward carrier of the Antarctic Intermediate Water and the Atlantic Meridional Overturning Circulation over the last 80 kyr, with a negative relationship at the beginning of Marine Isotope Stage 3 and over the Holocene. This contribution states that the positive relationship between the Antarctic Intermediate Water and the Atlantic Meridional Overturning Circulation is a dynamic interconnection that needs to be further constrained by future works.

Automated summary

Understanding the variations in the northward flow of the Antarctic Intermediate Water is crucial for comprehending the Atlantic Meridional Overturning Circulation. This study investigates the temporal changes in the flow speed of the Intermediate Western Boundary Current, the carrier of the Antarctic Intermediate Water, over the past 80,000 years. The results suggest a strong relationship between the northward transport of the Antarctic Intermediate Water and the Atlantic Meridional Overturning Circulation, with significant variations during different stages. Further research is needed to better understand this dynamic interconnection.