Holocene break-up and reestablishment of the Petermann Ice Tongue, Northwest Greenland

We reconstruct palaeoclimate and palaeoceanography of the Isafjarðardjup fjord system from two cores – one from the inner fjord and one near the fjord mouth – while separating the potential overprinting of relative sea-level (RSL) and local fjord hydrographic changes on these records. The inner fjord core (B997-339) reflects local fjord hydrography; the outer fjord core (MD99-2266) reflects the regional oceanic signal. Glacial marine conditions ended at ca. 10 200 cal. a BP, indicated by both ice-rafted debris records. The other proxy records show spatial and temporal variability within the fjord system. At the inner fjord site (B997-339) foraminiferal assemblages and the δ18O record indicate lowered RSL between ca. 10 600 and 8900 cal. a BP and document the onset of fjord water overturning at ca. 8900 cal. a BP, which obscured the climate record. At the fjord mouth (MD99-2266) mass accumulation rates suggest lowered RSL between ca. 10 200 and 5500 cal. a BP and local freshwater and/or reduced salinities of the Irminger Current water masses affected the δ18O signal between ca. 10 200 and 7900 cal. a BP. At MD99-2266, foraminiferal fauna record the Holocene Thermal Maximum between ca. 8000 and 5700 cal. a BP and the onset of modern oceanic circulation at ca. 7000 cal. a BP. Copyright © 2010 John Wiley & Sons, Ltd.

Reconstructing Holocene palaeoclimate and palaeoceanography in Ìsafjarðardjúp, northwest Iceland, from two fjord records overprinted by relative sea-level and local hydrographic changes

. In the area of Denmark Strait (~66° N), the two modes of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are expressed in changes of the northward flux of Atlantic water and the southward advection of polar water in the East Iceland current. Proxies from marine cores along an environmental gradient from extensive to little or no drift ice, capture low frequency variations over the last 2000 cal yr BP. Key proxies are the weight% of calcite, a measure of surface water stratification and nutrient supply, the weight% of quartz, a measure of drift ice transport, and grain size. Records from Nansen and Kangerlussuaq fjords show variable ice-rafted debris (IRD) records but have distinct mineralogy associated with differences in the fjord catchment bedrock. A comparison between cores on either side of the Denmark Strait (MD99-2322 and MD99-2269) show a remarkable millennial-scale similarity in the trends of the weight% of calcite with a trough reached during the Little Ice Age. However, the quartz records from these two sites are quite different. The calcite records from the Denmark Strait parallel the 2000 yr Arctic summer-temperature reconstructions; analysis of the detrended calcite and quartz data reveal significant multi-decadal–century periodicities superimposed on a major environmental shift occurring ca. 1450 AD.

https://cp.copernicus.org/articles/10/325/2014/cp-10-325-2014.pdf

Multidecadal to millennial marine climate oscillations across the Denmark Strait (~ 66° N) over the last 2000 cal yr BP

27 28 A suite of cores from the Northwest Iceland and East Greenland shelves sampled 29 fossiliferous or unfossiliferous basal glacial diamictons. Radiocarbon dates above the 30 diamictons are similar on both shelves, however, the value of the ocean reservoir 31 correction, ∆R, is unknown. Deglaciation occurred either ~16 or 14 cal ka BP depending 32 on the choice of ∆R. The ice sheets were behind the present coastline by 12.2 cal ka BP. 33 We examine seven cores that record the glacial/deglacial transition and present new data 34 on the sea-ice biomarkers IP25 and C25:2 from four of the cores plus data on IRD counts, 35 grain-size spectra, δ O on the near-surface planktonic foraminifera Neogloboquadrina 36 pachyderma (s), foraminifera assemblages, and quartz %. IP25 concentrations are 37 markedly higher for the East Greenland sites, while they are frequently below the limit of 38 quantification off Iceland; observations that parallel the wt% quartz in the sediments. 39 The δO N. pachyderma (s) data show a strong gradient across Denmark Strait with 40 lighter δO values towards the East Greenland shelf indicative of a large freshwater flux. 41 The presence of the chilled Atlantic Water benthic foraminifera, Cassidulina neoteretis, 42 indicates that rapid ice sheet retreat was associated with ocean forcing, combined with 43

Sea ice, ice-rafting, and ocean climate across Denmark Strait during rapid deglaciation (∼16-12 cal ka BP) of the Iceland and East Greenland shelves

Radiocarbon-dated marine cores, measurements of sediment density and seismic surveys were used to estimate the sediment and mass accumulation rates (m/kyr and kg/m2/kyr) in the troughs from the southwest to north-central Iceland shelf (i.e. northwest sector of Iceland). The 3.5-kHz seismic survey showed varying thicknesses of acoustically transparent sediment in the troughs, whereas the inter-trough banks were largely devoid of sediment. The survey showed a pervasive reflector 1 to ≥ 60 m below the sea floor, which turned out to be Saksunarvatn tephra, dated at 10 180 ± 60 cal. yr BP. The 3.5-kHz analogue data were digitized at 1-min intervals and provided 1645 estimates of maximum sediment thickness and 979 estimates of sediment accumulation over the last 10200 cal. yr BP. Maximum sediment accumulation occurred in the mid-troughs and not, as expected, in the fjords. The median sediment accumulation rate (SAR) based on the core data was 0.23 m/kyr, but was 0.77 m/kyr based on the seismic data: the difference is attributed to coring limitations. Based on the volume of offshore sediment and the contributing terrestrial drainage area, the Holocene denudation of northern Iceland (c. 50 000 km2) is calculated to have been between 0.02 to 0.05 m/kyr, substantially lower that the 1–3 m/kyr derived from the suspended sediment load of rivers from southern Iceland but in agreement with the rate of accumulation of Holocene glacial lacustrine sediments in central Iceland.

Holocene denudation of the northwest sector of Iceland as determined from accumulation of sediments on the continental margin

Date List X contains an annotated listing of 213 radiocarbon dates determined on samples from marine and terrestrial environments. The marine samples were collected from the East Greenland, Iceland, Spitzbergen, and Norwegian margins, Baffin Bay, and Labrador Sea. The terrestrial samples were collected from Vestfirdir, Iceland and Baffin Island. The samples were submitted by INSTAAR and researchers affiliated with INSTAAR's Micropaleontology Laboratory under the direction of Dr.’s John T. Andrews and Anne E. Jennings. All of the dates from marine sediment cores were determined from either shells or foraminifera (both benthic and planktic). All dates were obtained by the Accelerator Mass Spectrometry (AMS) method. Regions of concentrated marine research include: Baffin Bay, Baffin Island, Labrador Sea, East Greenland fjords, shelf and slope, Denmark Strait, the southwestern and northwestern Iceland shelves, and Vestfirdir, Iceland. The non-marine radiocarbon dates are from peat, wood, plant microfossils, and mollusc. The radiocarbon dates have been used to address a variety of research objectives such as: 1. determining the timing of northern hemisphere high latitude environmental changes including glacier advance and retreat, and 2. assessing the accuracy of a fluctuating reservoir correction. Thus, most of the dates constrain the timing, rate, and interaction of late Quaternary paleoenvironmental fluctuations in sea level, glacier extent, sediment input, and changes in ocean circulation patterns. Where significant, stratigraphic and sample contexts are presented for each core to document the basis for interpretations.

/pdf/radiocarbon-date-list-x-baffin-bay-baffin-island-iceland-1hx3dhzuhw.pdf

Radiocarbon Date List X: Baffin Bay, Baffin Island, Iceland, Labrador Sea, and the Northern North Atlantic

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Radiocarbon Date List X: Baffin Bay, Baffin Island, Iceland, Labrador Sea, and the Northern North Atlantic