Late glacial retreat of the Lancaster Sound Ice Stream and early Holocene onset of Arctic/Atlantic throughflow in the Arctic island channels

Multiple proxies in three sediment cores from Northwestern Baffin Bay document the timing of Lancaster Sound Ice Stream (LSIS) retreat that led to Arctic-Atlantic throughflow in Parry Channel, an important source of freshwater that can impact the Atlantic Meridional Overturning Circulation. The Late Glacial to Holocene timing of ice retreat and channel opening and the responses of the regional ocean environment to these events are presented. We use quantitative mineral composition, foraminiferal assemblages, biogenic silica, ice-rafted debris (IRD), and C-14-based age models to document and date the events and environmental changes occurring during deglaciation of this major marine channel. Findings show that retreat of the LSIS into Lancaster Sound occurred before similar to 15.3 cal ka BP, about 800 years before the onset of major iceberg calving events from the LSIS, named the Baffin Bay Detrital Carbonate events (BBDC 1 and BBDC 0). The end of BBDC 0 occurred at similar to 10.6 cal ka BP, which coincides with the opening of Parry Channel. A marine environment productive of calcareous benthic and planktic foraminifera, with diminished meltwater, seasonal sea ice, warmer summer temperatures, and inflowing, nutrient-rich Arctic surface water characterizes the interval between the opening of Parry Channel and the opening of Nares Strait. Paired planktic and benthic C-14 ages over this 2,200-year interval show diminishing age offsets suggesting progressive mixing of the upper similar to 850-900 m of the water column. The opening of Nares Strait by similar to 8.2 cal ka BP coincides with increased biogenic silica in the form of abundant, large centric diatoms and dissolution of CaCO3. The paucity of calcareous organisms after 8.2 cal ka BP resulted in poor chronological control in the cores to interpret changing environments after 8.2 cal ka BP.

Automated summary

The timing of ice retreat and channel opening in Northwestern Baffin Bay and its impact on the regional ocean environment are documented using various proxies. The retreat of the Lancaster Sound Ice Stream (LSIS) occurred before major iceberg calving events, and the opening of Parry Channel coincided with the end of one of these events. The opening of Nares Strait was associated with increased biogenic silica and dissolution of CaCO3.