Northeast Greenland: ice‐free shelf edge at 79.4°N around the Last Glacial Maximum 25.5–17.5 ka

Abstract

The size of the last glacial ice sheet on the Northeast (NE) Greenland shelf and its interaction with ocean circulation have been the subject of debate. Here we provide insights into the extent of the ice sheet around the Last Glacial Maximum (LGM) and investigate timing and strength of changes in the flow of Atlantic Water. The study is based on a multiproxy investigation of a marine sediment core, gravity core DA17-NG-ST01-019G, from 323-m water depth at the NE Greenland shelf edge at 79.4°N. We present benthic and planktic foraminiferal distribution data, AMS-14 C dates, sedimentological (ice-rafted debris (IRD) and grain sizes), and geochemical (XRF) data in combination with geophysical (sub-bottom profiler) data. The oldest sediments at the study site are dated to 25.5-17.5 ka, encompassing the time frame from the beginning of the LGM to the early deglaciation. This part is overlain by sediments from the late deglaciation and Holocene. The deposits dating from the LGM are very rich in both planktic and benthic foraminifera and macrofossils of excellent preservation. The faunas show that the site generally was affected by a strong flow of relatively warm subsurface Atlantic Water during the LGM and Early Holocene. Conditions turned more polar with cold bottom water flow in the Middle-Late Holocene (c. 7.5 ka to Recent) with presence of mainly agglutinated benthic foraminiferal species. Our data from the LGM also indicate that the deposits were mixed by iceberg scouring, confirmed by the geophysical data showing extensive ploughing of the sediments on the outer shelf area. The results further indicate that the Greenland Ice Sheet did not reach to the edge of the NE Greenland shelf at 79.4°N during the LGM 24-18 ka.

Paleoceanography of the Northwestern Greenland Sea and Return Atlantic Current evolution, 35–4 kyr BP

“…The slight decrease in benthic δ 18 O also suggest comparatively warm bottom conditions possibly due to the expansion of the warm AW. This is in accordance with recent findings of the presence of warm AW at the NE Greenland shelf (Rasmussen et al, 2022). The % of the planktic foraminifera N. pachyderma increases slightly and indicates presence of cold, polar surface water (Fig.…”

“…Evidence of a similar rapid retreat with similar timing is reported in the NE GIS (Arndt et al, 2017) and the Barents Sea and Fennoscandian ice sheets (Lekens et al, 2005;Rørvik et al, 2010). Intense deglacial iceberg rafting at the outer NE Greenland shelf has also been reported by previous studies by ploughmarks on the shelf (Arndt et al, 2017;Rasmussen et al, 2022). A relatively high % of current indicator species during this period is suggested to indicate the presence of strong, probably cold bottom currents (Fig.…”

“…However, the trend from the previous time interval 26 -~24 kyr BP of cooling with some influence of AW is indicated by the continuous presence of the AAW indicator species. The similar continuous flux of AW to the NE Greenland shelf during this period was also reported by Rasmussen et al (2022). In addition, the very low foraminiferal fluxes coincide with extremely low sedimentation rate and low IRD flux (Fig.…”

“…4), suggesting the presence of extensive sea-ice cover at the NE Greenland shelf during the LGM and early deglaciation. This near-permanent sea-ice cover, especially during the LGM and early deglaciation is also reported in a records from the NE Greenland shelf (Rasmussen et al, 2022) and Fram Strait (Müller et al, 2009).…”

Holocene history of the 79° N ice shelf reconstructed from epishelf lake and uplifted glaciomarine sediments

“…Raised glaciomarine deposits around Blåsø provide clear evidence of a complete deglaciation of the ∼ 70 km long Nioghalvfjerdsfjorden from a more advanced Late Glacial configuration (Fig. 11a; Winkelmann et al, 2010;Rasmussen et al, 2022). The onset of deglaciation -and the earliest evidence of the absence of the 79 • N ice shelf -is constrained by the deposition of mollusc-bearing glaciomarine sediments (BUG/LF1).…”