Description: Palynological, geochemical, and physical records were used to document Holocene paleoceanographic changes in marine sediment core from Dease Strait in the western part of the main axis of the Northwest Passage (core 2005-804-006 PC latitude 68°59.552'N, longitude 106°34.413'W). Quantitative estimates of past sea surface conditions were inferred from the modern analog technique applied to dinoflagellate cyst assemblages. The chronology of core 2005-804-006 PC is based on a combined use of the paleomagnetic secular variation records and the CALS7K.2 time-varying spherical harmonic model of the geomagnetic field. The age-depth model indicates that the core spans the last ~7700 cal years B.P., with a sedimentation rate of 61 cm/ka. The reconstructed sea surface parameters were compared with those from Barrow Strait and Lancaster Sound (cores 2005-804-004 PC and 2004-804-009 PC, respectively), which allowed us to draw a millennial-scale Holocene sea ice history along the main axis of the Northwest Passage (MANWP). Overall, our data are in good agreement with previous studies based on bowhead whale remains. However, dinoflagellate sea surface based reconstructions suggest several new features. The presence of dinoflagellate cysts in the three cores for most of the Holocene indicates that the MANWP was partially ice-free over the last 10,000 years. This suggests that the recent warming observed in the MANWP could be part of the natural climate variability at the millennial time scale, whereas anthropogenic forcing could have accelerated the warming over the past decades. We associate Holocene climate variability in the MANWP with a large-scale atmospheric pattern, such as the Arctic Oscillation, which may have operated since the early Holocene. In addition to a large-scale pattern, more local conditions such as coastal current, tidal effects, or ice cap proximity may have played a role on the regional sea ice cover. These findings highlight the need to further develop regional investigations in the Arctic to provide realistic boundary conditions for climatic simulations.

Description: Two cores, one from the Beaufort Sea Slope at 1000 m water depth (core 750) and one from the Amundsen Gulf at 426 m (core 124), were collected to help determine paleo-ice cover in the Holocene and late glacial of this area. Site 750 is particularly sensitive to changes in paleo-ice cover because it rests beneath the present ice margin of the permanent Arctic ice pack. Core 124 was sampled just in front of the former glacier that moved out into the Amundsen Gulf and started to recede about 13 ka B.P. Both cores have a strong occurrence of calcareous foraminifera in the upper few centimeters, but these disappear throughout most of the Holocene, suggesting more open water in that time period than present. In the sediments representing the end of the last glacial period (dated at ~11,500-14,000 calibrated years B.P. (cal B.P.)) a calcareous fauna with an abundant planktic foraminiferal fauna suggests a return to almost permanent ice cover, much like the central Arctic today. Together with the foraminifera there was also abundant ice-rafted debris (IRD) in both cores between 12,000 cal B.P. and ~14,000 cal B.P., but those units are of different ages between cores, suggesting different events. The IRD in both cores appears to have the same magnetic and chemical signals, but their origins cannot be determined exactly until clay mineralogy is completed. There is abundant organic debris in both cores below the IRD units: the organics in core 750 are very diffuse and not visually identifiable, but the organic material in core 124 is clearly identifiable with terrestrial root fragments; these are 14C dated at over 37,000 years B.P. This is a marine unit as it also has glacial front foraminifera in the sediment with the organic debris that must have been originating from subglacial streams. The seismic and multibeam data both indicate glaciers did not cross the core 124 site.

Description: The data presents field sampling undertaken at Nazareth tidal flat and marsh located west of Rimouski on the southern shore of Lower St. Lawrence Estuary (Canada). Three cross shore transects (A, B, C) were established with a total of 29 stations covering high marsh, low marsh, mudflat and sandflat. Grain size distribution and organic matter content (loss on ignition) of surface scrape sediments were analyzed in summer 2016 and summer 2018.

Description: The mineralogical and geochemical compositions of three sediment cores from the northwestern Greenland continental margin (204, 210) and Kane Basin (Kane2B) were investigated to document the impact of ice-ocean interactions on the sediment provenance and transport pathways during the Holocene.

Description: The data presents field sampling undertaken at Nazareth tidal flat and marsh located west of Rimouski on the southern shore of Lower St. Lawrence Estuary (Canada). Three cross shore transects (A, B, C) were established with a total of 29 stations covering high marsh, low marsh, mudflat and sandflat. The erodability of sediment was measured with a cohesive strength meter (CSM Mk IV) in terms of critical erosion threshold (n=5). Measurements for the annual changes in critical erosion threshold were conducted in three consecutive summers on transects A, B, C in 2016 (9-11 August), 2017 (23-25 August) and on transect B in 2018 (6 September).

Description: Erosion threshold (n=5) of surface sediment was measured with a cohesive strength meter (CSM Mk IV) to determine seasonal and spatial changes in sediment erodibility at Nazareth tidal flat and marsh located west of Rimouski on the southern shore of Lower St. Lawrence Estuary (Canada). Multiple field campaigns were conducted at three cross shore transects (A, B, C) in summer 2016 (8, 9, 10 August), summer 2017 (23, 24, 25 August), with subsequent campaigns at B Transect in autumn 2017 (22, 25 November), winter 2018 (16, 20 February), spring 2018 (30 May), and summer 2018 (6 September). The data presented here does not contain the summer field campaigns, which was published in the context of annual variations in sediment erodibility (Waqas et al., 2019, https://doi.org/10.1594/PANGAEA.911769).

Description: Grain size distribution and organic matter content (loss on ignition) of surface scrape sediments were analyzed in summer 2016, autumn 2017, and summer 2018 at Nazareth tidal flat and marsh located west of Rimouski on the southern shore of Lower St. Lawrence Estuary (Canada). Surface sediment samples for analysis of grain size and organic matter content were collected at each site within 1 m radius of CSM measurements using a spatula to scrape the top 2-3 cm of sediments. The combustible organic matter content (loss on ignition, LOI) of the surface sediments was determined after: (1) drying at 60°C for 24 h until no weight change occurred; (2) placing in oven at 450°C for 16 h. For grain size analysis, the coarse and the fine grain size distributions were processed with Gradistat (Blott and Pye, 2001) to compute median grain size (d50), mean grain size, and sorting using the geometric moment method. The sorting is calculated similarly to a standard deviation. Cross-shore transect B was sampled in November 2017 for which, the data is presented here. The data for summer 2016, summer 2017, and summer 2018 was published in the context of annual variations in sediment biostabilization (Waqas et al., 2019, doi:10.1594/PANGAEA.911771)

Description: A sediment-sampling program was carried out in the Nares Strait region during the Nares 2001 Expedition to obtain cores for high-resolution palaeoceanographic studies of late Pleistocene-Holocene climate change. Long cores (〉4 m) were obtained from basins near Coburg Island, Jones Sound, John Richardson Fiord off Kane Basin, and in northeastern Hall Basin. Short cores and grab samples were taken on shelves east and west of northern Smith Sound and in Kennedy Channel. Detailed studies of sediment texture, stable isotopes, microfossils and palynomorphs were made on the longest cores from Jones Sound and Hall Basin at the southern and northern ends of the Nares Strait region.