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ABSTRACT: A suite of cores from the North‐West Iceland and East Greenland shelves sampled fossiliferous or unfossiliferous basal glacial diamictons. Radiocarbon dates above the diamictons are similar on both shelves, but the value of the ocean reservoir correction, ΔR, is unknown. Deglaciation occurred either ∼16 or 14 cal ka BP depending on the choice of ΔR. The ice sheets were behind the present coastline by 12.2 cal ka BP. We examine seven cores that record the glacial/deglacial transition and present new data on the sea‐ice biomarkers IP25 and C25:2 from four of the cores plus data on ice‐rafted debris counts, grain‐size spectra, δ18O on the near‐surface planktonic foraminifera Neogloboquadrina pachyderma (s), foraminifera assemblages, and quartz percentage. IP25 concentrations are markedly higher for the East Greenland sites, while they are frequently below the limit of quantification off Iceland, observations that parallel the wt% quartz in the sediments. The δ18O N. pachyderma (s) data show a strong gradient across Denmark Strait with lighter δ18O values towards the East Greenland shelf indicative of a large freshwater flux. The presence of the chilled Atlantic Water benthic foraminifera, Cassidulina neoteretis indicates that rapid ice sheet retreat was associated with ocean forcing, combined with other factors. [ABSTRACT FROM AUTHOR]

Sub-Arctic habitats are being exposed to increasingly long periods of open water as sea ice continues to decline in thickness and extent. Some hypothesize that this will result in a reduction, and maybe total loss of sea ice derived (sympagic) carbon supply; however, the impact of such change on ecosystems requires further investigation. Here, we used the H-Print biomarker approach that utilizes well-defined indicators of both sympagic and phytoplanktic carbon, in combination with stable isotopes (δ15N), to study the effect of reducing sympagic carbon availability on beluga whales ( Delphinapterus leucas) in the sub-Arctic ecosystem of Cumberland Sound. Our data show that decreasing δ15N in belugas was negatively correlated with pelagic carbon (H-Print) within their diet. We also identified a statistically significant ( R2 = 0.82; p ≤ 0.01) change point in the proportion of sympagic/pelagic carbon within beluga around the year 2000, signified by consistently reducing δ15N, coupled with increasing pelagic carbon composition. This observed shift from sympagic to pelagic contribution to diet is likely to remain a feature of the Cumberland Sound ecosystem during the projected reduction of sea ice. [ABSTRACT FROM AUTHOR]

We describe the results of an inter-laboratory investigation into the identification and quantification of the Arctic sea ice biomarker proxy IP25 in marine sediments. 7 laboratories took part in the study, which consisted of the analysis of IP25 in a series of sediment samples from different regions of the Arctic, sub-Arctic and Antarctic, additional sediment extracts and purified standards. The results obtained allowed 4 key outcomes to be determined. First, IP25 was identified by all laboratories in sediments from the Canadian Arctic with inter-laboratory variation in IP25 concentration being substantially larger than within individual laboratories. This greater variation between laboratories was attributed to the difficulty in accurately determining instrumental response factors for IP25, despite provision of appropriate standards. Second, the identification of IP25 by 3 laboratories in sediment from SW Iceland that was believed to represent a blank, was interpreted as representing a better limit of detection or quantification for such laboratories, contamination or mis-identification. These alternatives could not be distinguished conclusively with the data available, although it is noted that the precision of these data was significantly poorer compared with the other IP25 concentration measurements. Third, 3 laboratories reported the occurrence of IP25 in a sediment sample from the Antarctic Peninsula even though this biomarker is believed to be absent from the Southern Ocean. This anomaly is attributed to a combined chromatographic and mass spectrometric interference that results from the presence of a di-unsaturated highly branched isoprenoid (HBI) pseudo-homologue of IP25 that occurs in Antarctic sediments. Finally, data are presented that suggest that extraction of IP25 is consistent between Automated Solvent Extraction (ASE) and sonication methods and that IP25 concentrations based on 7-hexylnonadecane as an internal standard are comparable using these methods. Recoveries of some more unsaturated HBIs and the internal standard 9-octylheptadecene, however, were lower with the ASE procedure, possibly due to partial degradation of these more reactive chemicals as a result of higher temperatures employed with this method. For future measurements, we recommend the use of reference sediment material with known concentration(s) of IP25 for determining and routinely monitoring instrumental response factors. Given the significance placed on the presence (or otherwise) of IP25 in marine sediments, some further recommendations pertaining to quality control are made that should also enable the two main anomalies identified here to be addressed. [ABSTRACT FROM AUTHOR]

In order to elucidate a continuous Holocene high resolution record of past variability of Atlantic water inflow and sea ice distribution, we investigate in this study a marine sediment core (JM09-KA11-GC) from the Kveithola Trough, western Barents Sea margin which is influenced by the north flowing North Atlantic Current (NAC). The depth-age model for JM09-KA11-GC was constructed from 9 14C AMS dates and shows sediment accumulation rates from 0.04 to 0.67 mmyr-1, enabling a sub centennial resolution for most of the core. Planktic foraminifera, stable isotopes and biomarkers from sea ice diatoms and phytoplankton were analysed in order to reconstruct subsurface temperatures and sea ice distribution. Throughout the early part of the Holocene (11 900-6900 cal yr BP), the foraminiferal fauna is dominated by the polar Neogloboquadrina pachyderma (sinistral) and the biomarkers show an influence of seasonal sea ice. Between 11 300 and 11 100 cal yrBP, a clear cooling is shown both by fauna and stable isotope data corresponding to the so-called Preboreal Oscillation. After 6900 cal yrBP the subpolar Turborotalita quinqueloba becomes the most frequent species, reflecting a stable Atlantic water inflow. Subsurface temperatures reach 6 °C and biomarker content indicates open water with mainly ice-free conditions. During the last 1100 cal yrBP, biomarker abundances and distributions show the re-appearance of low frequency seasonal sea ice and the planktic fauna show a reduced salinity in the subsurface water. No apparent temperature decrease is observed during this interval, but the rapidly fluctuating fauna and biomarker distributions indicate more unstable conditions. [ABSTRACT FROM AUTHOR]

MD99-2263 is a 46 cm box core collected from Djupall, a trough that cuts across the NW Iceland Shelf and ends above Denmark Strait. We provide a multiproxy record that documents changes in the regional marine climate over the last ∼1700 yr. The depth/age model is based on seven calibrated radiocarbon dates on mollusk shells and on 210Pb and 137Cs. Sediment accumulation rates were variable (0.2-0.8 mm/yr) but increased dramatically ∼AD 1500. Grain-size, magnetic properties, quantitative mineral composition of the <2 mm sediment fraction, benthic foraminiferal composition, benthic and planktic δ18O ratios, and abundances/fluxes of the sea ice biomarker IP25 were determined. To better compare the various proxies, 12 of the critical climate proxies were co-ordinated into 100-yr/sample time series, which were examined by Principal Component Analysis. The 1st axis explained 49% of the variance and the 2nd axis explained an additional 17%. The variables most strongly associated with the 1st axis were sediment properties (phi mean, clay%) and the sea ice biomarker. Mineralogical indicators of drift ice rafting, such as the presence of quartz and potassium- and sodiumfeldspars, coincide with the IP25 biomarker data and show an increase after AD 1200, but high values of quartz and some feldspars also occurred between c. AD 300 and 900 with pronounced minima between AD 900 and 1100. Overall, our data suggest a simple two-fold division in climate conditions over the last 1700 yr, with the major change occurring c. AD 1200. In the last few decades, conditions have reverted towards those experienced prior to AD 1200. [ABSTRACT FROM AUTHOR]