Linkages between ocean circulation and the Zachariae Isstrøm in the Early Holocene

It is unequivocal that the climate is changing; marine terminating glaciers in Northeast Greenland (NEG) have experienced rapid speedup and retreat in recent decades as a result. The Zachariae Isstrøm (ZI) began accelerating in 2000, resulting in the total collapse of its floating ice tongue. This has been partly attributed to basal melting caused by the warming of Atlantic Water (AW). Unfortunately, our understanding of the interaction between these entities is somewhat limited by the length of instrumental records. Examining proxies preserved in marine sediment cores provides an alternative method to understand these changes on longer timescales.

Here we apply a multi-proxy approach (XRF, benthic foraminifera, stable isotopes, grain size, CT scans) to marine sediment core DA17-NG-ST08-092G, collected from the NEG continental shelf, 90km east of the ZI terminus. Our results indicate that the site was free of grounded ice at least as early as 12.5 ka cal BP, and most likely before 13.4 ka cal BP. The inflow of AW onto the continental shelf may have played a role in the seemingly early deglaciation at this site. Between 13.4 and 11.2 ka cal BP the site was overlain by a floating ice tongue, most likely the ZI, with AW and PW flowing beneath. Following this, the ZI briefly retreated westwards (11.2-10.8 ka cal BP) before it re-advanced (10.8-9.6 ka cal BP); there was a strong influx of AW throughout these periods. Between 9.6 and 7.9 ka cal BP the ZI retreated westwards again, before a drastic shift in ocean circulation occurred at 7.9 ka cal BP. At this time, there was a sharp decline in AW corresponding to an increase in PW flowing beneath perennial sea ice. In the final part of the record, AW returns and there was likely a breakup of the perennial sea ice.