Sub-precessional pacing of ice conditions and organic carbon burial in the Ross Sea, Antarctica, during the mid-Pliocene Warm Period

For over 200 ka during the mid-Pliocene Warm Period (mPWP), sustained high atmospheric pCO₂ (> 350 ppm) maintained global temperatures above pre-industrial levels. Nonetheless, as documented here, ice growth pulses occurred during this interval along the margin of the West Antarctic Ice Sheet, impacting the carbon cycle. These events resulted in high amplitude changes in the source and burial rate of organic carbon (Corg) in the Ross Sea. Warm intervals with seasonally open sea-ice conditions were recorded by thick, greenish, diatom-rich sediments containing relatively abundant marine Corg. Cold intervals, assigned to perennial ice cover pulses, were recorded by grayish, decimeter-thick layers with very low Corg content, likely relating to the erosion of sedimentary rocks on land. Although the obliquity forcing is evident in the sequence, the cold pulses occurred at a much higher frequency (~ 16 ka), not matched by any direct precession insolation control, thus involving the interference of complex glaciological, oceanic and atmospheric processes which warrant closer examination. Remarkably, even under the "warm Earth scenario" of the mPWP, these processes have sustained perennial ice cover pulses beyond the continental Ross Sea shelf limit.