Fig. 7: Ocean cavity regime shift as a mechanism for West Antarctic Ice Sheet (WAIS) retreat and readvance.

a Paleoclimate reconstructions from Antarctic ice core records. The gray bar indicates the presence of Southern Elephant Seals (SES) in the Western Ross Sea region of Antarctica, which indicate reduced land-fast sea ice⁵⁹. The black sections denote especially warm periods. The green line shows Methanesulfonic acid concentrations (MSA) at Taylor Dome^58,90, a proxy for marine biological productivity related to polynya activity. The purple line shows a reconstruction of summer temperature anomalies (STA) from the WAIS Divide ice core (WDC) from ref. ⁶⁰. The approximate timing of grounding line retreat (-R) and advance (-A) is indicated for the WAIS subglacial sediment sites. The background colors correspond to approximate timings of ice sheet phases: early Holocene retreat to the modern grounding line position (blue), middle Holocene retreat to the minimum grounding line position (yellow), and late Holocene advance to the modern grounding line position (pink). The overlapping yellow and pink represent the uncertainty in the precise timing of cold cavity initiation and with the acknowledgment that regional differences may exist. The timing is based on the long-term increase in Ross Sea polynya efficiency from 3.6 ka BP²¹, though centennial-scale oscillations in polynya efficiency and mCDW intrusion do occur through this interval^47,59, until the time of ice stream advance indicated in pink from 1.6 ka BP. b–d Ice shelf/ice sheet transects along Bindschadler Ice Stream (BIS) for the ice sheet phases above. The gray bar indicates sea ice extent. Red shading indicates the location of mCDW. The purple arrow indicates direction of grounding line change. The size of the black arrow corresponds to the strength of katabatic winds.