Late Quaternary sedimentary processes in the central Arctic Ocean inferred from geophysical mapping

Cryospheric events in the Arctic Ocean have been largely studied through the imprints of ice sheets, ice shelves and icebergs in the seafloor morphology and sediment stratigraphy. Subglacial morphologies have been identified in the shallowest regions of the Arctic Ocean, up to 1200 m water depth, revealing the extent and dynamics of Arctic ice sheets during the last glacial periods. However, less attention has been given to sedimentary features imaged in the vicinity of the ice-grounded areas. Detailed interpretation of the sparse available swath bathymetry and sub-bottom profiles from the Lomonosov Ridge and the Amundsen Basin shows the occurrence of mass transport deposits (MTDs) and sediment waves in the central Arctic Ocean. The waxing and waning ice sheets and shelves in the Arctic Ocean have influenced the distribution of MTDs in the vicinity of grounding-ice areas, i.e. along the crest of Lomonosov Ridge. Due to the potential of Arctic sediments to hold gas hydrates, their destabilization should not be ruled out as trigger for sediment instability. Sediment waves formed by the interaction of internal waves that propagate along water mass interfaces with the bathymetric barrier of Lomonosov Ridge. This work describes the distribution and formation mechanisms of MTDs and sediment waves in the central Arctic Ocean in relation to grounding ice and internal waves between water masses respectively. The distribution of these features provides new insight into past cryospheric and oceanographic conditions of the central Arctic Ocean

Glacial sedimentation, fluxes and erosion rates associated with ice retreat in Petermann Fjord and Nares Strait, north-west Greenland

Petermann Fjord is a deep (>1000 m) fjord that incises the coastline of north-west Greenland and was carved by an expanded Petermann Glacier, one of the six largest outlet glaciers draining the modern Greenland Ice Sheet (GrIS). Between 5 and 70 m of unconsolidated glacigenic material infills in the fjord and adjacent Nares Strait, deposited as the Petermann and Nares Strait ice streams retreated through the area after the Last Glacial Maximum. We have investigated the deglacial deposits using seismic stratigraphic techniques and have correlated our results with high-resolution bathymetric data and core lithofacies. We identify six seismo-acoustic facies in more than 3500 line kilometres of sub-bottom and seismic-reflection profiles throughout the fjord, Hall Basin and Kennedy Channel. Seismo-acoustic facies relate to bedrock or till surfaces (Facies I), subglacial deposition (Facies II), deposition from meltwater plumes and icebergs in quiescent glacimarine conditions (Facies III, IV), deposition at grounded ice margins during stillstands in retreat (grounding-zone wedges; Facies V) and the redeposition of material downslope (Facies IV). These sediment units represent the total volume of glacial sediment delivered to the mapped marine environment during retreat. We calculate a glacial sediment flux for the former Petermann ice stream as 1080–1420 m3 a−1 per metre of ice stream width and an average deglacial erosion rate for the basin of 0.29–0.34 mm a−1. Our deglacial erosion rates are consistent with results from Antarctic Peninsula fjord systems but are several times lower than values for other modern GrIS catchments. This difference is attributed to fact that large volumes of surface water do not access the bed in the Petermann system, and we conclude that glacial erosion is limited to areas overridden by streaming ice in this large outlet glacier setting. Erosion rates are also presented for two phases of ice retreat and confirm that there is significant variation in rates over a glacial–deglacial transition. Our new glacial sediment fluxes and erosion rates show that the Petermann ice stream was approximately as efficient as the palaeo-Jakobshavn Isbræ at eroding, transporting and delivering sediment to its margin during early deglaciation

Initial observations of the shallow geology in Tannis Bugt, Skagerrak, Denmark

During August 2017, as part of the habitat mapping of Natura2000 areas, a geophysical survey of a large area within the Skagerrak was undertaken by the Geological Survey of Denmark and Greenland. In this article, we use the acquired data to discuss the geology of Tannis Bugt (Fig. 1), a large shallow bay at the north-west coast of Vendsyssel. The bay extends 40 km between Hirtshals in the west and Skagen in the east forming the northern-most Danish Skagerrak coast

Persistent symptoms up to four months after community and hospital-managed SARS-CoV-2 infection

The spectrum of recovery for people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains uncertain.1-4 The ADAPT study is a prospective cohort study that follows up all adults diagnosed with coronavirus disease 2019 (COVID-19) at St Vincent’s Hospital, Sydney. Our goal is to characterise the effects of infection during the 12 months after diagnosis, by initial severity of COVID-19. Our specific aims were to determine the prevalence and nature of persistent symptoms; to evaluate lung function, health-related quality of life, neurocognitive and olfactory abnormalities during the recovery period; and to characterise the longitudinal immune response to infection. In this article, we report the results of assessments performed up to four months after diagnosis. All adults with SARS-CoV-2 infections confirmed by polymerase chain reaction (PCR) at St Vincent’s Hospital testing clinics and who could be contacted were invited to participate. Participants were prospectively assessed according to a pre-defined schedule. The study was approved by the St Vincent’s Hospital Human Research Ethics Committee (reference, 2020/ETH00964); baseline visits commenced as soon as this approval was obtained

Retreat patterns and dynamics of the former Norske Trough ice stream (NE Greenland): An integrated geomorphological and sedimentological approach

Funding for this research was provided by the Independent Research Fund Denmark (grant no. 0135–00165 B (GreenShelf project)). The cruise was funding by the Danish Centre for Marine Research, the Engineering Research Council of Canada, and the Independent Research Fund Denmark (G-Ice Project (grant no. 7014-00113 B/FNU). A.L.-Q. also thanks the Spanish Ministry of Science and Innovation (MCIN) for Research Contract FJC 2021-047046-I (MCIN/AEI/10.13039/501100011033 and NextGenerationEU/PRTR).A better understanding of past extent and dynamics of the Greenland Ice Sheet (GrIS) is required to provide context for present-day observations, to constrain numerical climate models and to predict future scenarios of ice-sheet response to recent climatic change. The presence of a grounded GrIS on the NE Greenland shelf during the Last Glacial Maximum (LGM) is supported by high-resolution seismic data combined with multi-proxy analyses of sediment gravity cores from Norske Trough. Our results indicate that an ice stream advanced to the outer shelf during the LGM. Recessional moraines and grounding zone wedges on the seafloor of the outer to middle shelf show that initial retreat was episodic, punctuated by two major stillstands. Pinning points for grounding-zone stabilization were controlled by pre-LGM trough topography. In contrast, preserved large-scale glacial lineations on the seafloor of the inner shelf, formed during the advance, indicate that ice retreat from the inner trough to the coast-proximal position was rapid in order to maintain the former carved morphology. Initial ice retreat was underway before 16.6 cal Kyr BP, earlier than previously known for this sector of the NE Greenland shelf. The inner shelf was free from grounded ice at least by 12.5 cal Kyr BP, and likely before. Retreat occurred in a glaciomarine setting and the ice sheet was fringed by a floating ice shelf. There is no evidence of grounded-ice readvances during the Younger Dryas, although a floating ice shelf with vigorous sea-ice and iceberg rafting production occupied the inner shelf at 11.3 cal Kyr BP. 14C dates reveal initial stepwise ice retreat followed by a fast retreat that coincides with Heinrich Stadial 1 and the Bølling-Allerød interstadial, respectively. During both periods there was increased inflow of warm Atlantic Water, indicating a strong ocean/climate control on the late deglaciation of Norske Trough. Following the late deglaciation, postglacial (Holocene) sedimentation records a change from an ice-distal glaciomarine environment, to an open marine environment and complete ice shelf disintegration. On the innermost shelf of the Norske Trough, the ice shelf disintegrated and reformed once before the final break-up occurred at 9.6 cal Kyr BP.Independent Research Fund Denmark 0135–00165 BDanish Centre for Marine Research, the Engineering Research Council of CanadaIndependent Research Fund Denmark 7014-00113 B/FNUSpanish Ministry of Science and Innovation FJC 2021-047046-INextGenerationEU/PRT