ALBERT

Description: Determining the sensitivity of the Greenland Ice Sheet (GrIS) to Holocene climate changes is a key prerequisite for understanding the future response of the ice sheet to global warming. In this study, we present new information on the Holocene glacial history of the GrIS in Inglefield Land, north Greenland. We use 10Be and in situ 14C exposure dating to constrain the timing of deglaciation in the area and radiocarbon dating of reworked molluscs and wood fragments to constrain when the ice sheet retreated behind its present-day extent. The 10Be ages are scattered ranging from ca. 92.7 to 6.8 ka, whereas the in situ 14C ages range from ca. 14.2 to 6.7 ka. Almost half of the apparent 10Be ages predate the Last Glacial Maximum and up to 89 % are to some degree affected by nuclide inheritance. Based on the few reliable 10Be ages, the in situ 14C ages and existing radiocarbon ages from Inglefield Land, we find that the deglaciation along the coast commenced at ca. 8.6–8.3 ka cal BP in the western part and ca. 7.9 ka in the central part, following the opening of Nares Strait and arrival of warm waters. The ice margin reached its present-day position at ca. 8.2 ka at the Humboldt Glacier and ca. 6.7 ka in the central part of Inglefield Land. Radiocarbon ages of reworked molluscs and wood fragments show that the ice margin was behind its present-day extent from ca. 5.8 to 0.5 ka cal BP. After 0.5 ka cal BP, the ice advanced towards its Little Ice Age position. Our results emphasize that the slowly eroding and possibly cold-based ice in north Greenland makes it difficult to constrain the deglaciation history based on 10Be ages alone unless they are paired with in situ 14C ages. Further, combining our findings with those of recently published studies reveals distinct differences between deglaciation patterns of northwest and north Greenland. Deglaciation of the land areas in northwest Greenland occurred earlier than in north Greenland, and periods of restricted ice extent were longer, spanning the Middle and Late Holocene. Overall, this highlights past ice sheet sensitivity to Holocene climate changes in an area where little information was available just a few years ago.

Description: We present bathymetry and hydrological observations collected in the summer of 2014 from two fjord systems in southeastern Greenland with a multibeam sonar system. Our results provide a detailed bathymetric map of the fjord complex around the island of Skjoldungen in Skjoldungen Fjord and the outer part of Timmiarmiut Fjord and show far greater depths compared to the International Bathymetric Chart of the Arctic Ocean. The hydrography collected shows different properties in the fjords with the bottom water masses below 240 m in Timmiarmiut Fjord being 1–2 °C warmer than in the two fjords around Skjoldungen, but data also illustrate the influence of sills on the exchange of deeper water masses within fjords. Moreover, evidence of subglacial discharge in Timmiarmiut Fjord, which is consistent with satellite observations of ice mélange set into motion, adds to our increasing understanding of the distribution of subglacial meltwater. Data are available through the PANGAEA website at https://doi.pangaea.de/10.1594/PANGAEA.860627.

Description: We present bathymetry and hydrological observations collected in the summer of 2014 from two fjord systems in Southeast Greenland, using SS Activ with a multibeam system temporally installed over the side of the ship. Our results provide a detailed bathymetric map of the fjord complex around Skjoldungen Island and the outer part of Timmiarmiut Fjord and show far greater depths compared to the International Bathymetric Chart of the Arctic Ocean. The hydrography collected show different properties in the fjords with the bottom water masses below 240 m in Timmiarmiut Fjord being 1–2 °C warmer than in the two fjords around Skjoldungen Island, but data also illustrate the influence of sills on the exchange of deeper water masses within fjords. Moreover, evidence of subglacial discharge in Timmiarmiut Fjord, consistent with satellite observations of ice mélange set into motion, adds to our increasing understanding of the distribution of subglacial meltwater. Data is available through the PANGAEA website https://doi.pangaea.de/10.1594/PANGAEA.860627.