Local summer insolation modulated Southern Ocean productivity and Antarctic icesheet evolution since MIS 5

Abstract

The relationship of marine productivity in the Southern Ocean (SO) to dynamics of the Antarctic icesheet (AIS) since the Late Pleistocene remains uncertain. Here, we investigated Late Pleistocene variation in productivity in the Antarctic Zone of the SO, and the response of the AIS to various potential forcing mechanisms. We analyzed secular variation in multiple biogenic components and ice-rafted debris (IRD) of a sediment core (ANT34/D5–12) from the Atlantic sector of the SO. Productivity, as tracked by the fluxes of excess Ba and opal, was controlled mainly by local mean summer insolation, which also modulated icesheet dynamics, as revealed by IRD. These records nonetheless show distinct precessional variability (∼20 kyr cycle) related to austral summer insolation. During high (low) insolation intervals, productivity was high (low), and the AIS contracted (expanded). Based on these data and published paleoclimate records, we propose that marine productivity and icesheet dynamics during the Late Pleistocene were primarily controlled by local Antarctic summer mean insolation through regulation of water-column stratification depth. These findings support hypotheses for the independent evolution of Antarctic climate (i.e., not paced by Northern Hemisphere summer insolation) and provide new insights into biogeochemical cycling in the SO and AIS dynamics.