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A sediment core from the salt marsh fringing Loch Duart, NW Scotland, UK, containing Lateglacial to Holocene sediments, was analysed using a multi-element geochemical approach to elucidate the relative sea level (RSL) and palaeoenvironmental changes associated with the deglaciation of the British and Irish Ice Sheet. Elemental and isotopic measurements of rhenium, osmium, carbon and nitrogen, X-ray fluorescence scanning, radiocarbon dating, and foraminiferal analysis produced a suite of data that complements the existing biostratigraphic framework. This suite of bio-, litho- and chemostratigraphic analyses permits discussion of RSL changes that reflect the interplay between post-glacial eustatic rise and glacio-isostatic adjustment. The osmium-isotope (187Os/188Os) data, coupled with a new age-depth model, depict an RSL fall between 16.8 and 14.1 ka cal BP at an average rate of 2 mm a-1. Falling RSL culminates in basin isolation and is followed by subsequent marine inundation from 11.6 ka cal BP. This RSL record preserves the local interaction between glacial isostatic adjustment and glacio-eustatic sea-level change, a relationship that is reflected in the sediment's 187Os/188Os signature. This is the first known application of the osmium isotope system in an isolation basin that is shown to be a viable proxy for RSL change, a technique that could be applied to glacially influenced isolation basins globally. [ABSTRACT FROM AUTHOR]

The Northeast Greenland Ice Stream has recently seen significant change to its floating margins and has been identified as vulnerable to future climate warming. Inflow of warm Atlantic Intermediate Water (AIW) from the continental shelf has been observed in the vicinity of the Nioghalvfjerdsfjorden (79 ∘ N) Glacier calving front, but AIW penetration deep into the ice shelf cavity has not been observed directly. Here, we report temperature and salinity measurements from profiles in an epishelf lake, which provide the first direct evidence of AIW proximal to the grounding line of 79 ∘ N Glacier, over 50 km from the calving front. We also report evidence for partial un-grounding of the margin of 79 ∘ N Glacier taking place at the western end of the epishelf lake. Comparison of our measurements to those close to the calving front shows that AIW transits the cavity to reach the grounding line within a few months. The observations provide support for modelling studies that infer AIW-driven basal melt proximal to the grounding line and demonstrate that offshore oceanographic changes can be rapidly transmitted throughout the sub-ice-shelf cavity, with implications for near-future stability of the ice stream. [ABSTRACT FROM AUTHOR]

Describes an activity for high school students on household plastic wraps to introduce polymer science. Tests wraps for added plasticizers and stress and strain properties. Suggests focus points for student evaluation. (YDS)

The North-East Greenland Ice Stream has recently seen significant change to its floating margins, and has been identified as vulnerable to future climate warming. Inflow of warm Atlantic Intermediate Water (AIW) from the continental shelf has been observed in the vicinity of the Nioghalvfjerdsfjorden (79N) Glacier calving front, but AIW penetration deep into the ice shelf cavity has not been observed directly. Here, we report temperature and salinity measurements from profiles in an epishelf lake, which provide the first direct evidence of AIW proximal to the grounding line of 79N Glacier, over 50 km from the calving front. We also report evidence for partial un-grounding of the margin of 79N taking place at the western end of the epishelf lake. Comparison of our measurements to those close to the calving front shows that AIW transits the cavity to reach the grounding line within a few months. The observations provide support for modelling studies that infer AIW-driven basal melt proximal to the grounding line and demonstrate that offshore oceanographic changes can be rapidly transmitted throughout the sub-ice shelf cavity, with implications for near-future stability of the ice stream. [ABSTRACT FROM AUTHOR]

Nioghalvfjerdsbrae, or 79°N Glacier, is the largest marine-terminating glacier draining Northeast Greenland Ice Stream (NEGIS). In recent years, it's ~70km-long fringing ice shelf (hereafter referred to as 79°N ice shelf) has thinned, and a number of small calving events highlight its sensitivity to climate warming. With the continued retreat of 79°N ice shelf and the potential for accelerated discharge from NEGIS, which drains 16% of the Greenland Ice Sheet (GrIS), it has become increasingly important to understand the long-term history of the ice shelf in order to put the recent changes into perspective and to judge their long-term significance. Here we reconstruct the Holocene dynamics of 79°N ice shelf by combining radiocarbon dating of marine mollusc from isostatically uplifted glacimarine sediments with a multi-proxy investigation of two sediment cores recovered from Blåsø, a large epishelf lake 2-13 km from the current grounding line of 79°N Glacier. Our reconstructions suggest that the ice shelf retreated between 8.5 and 4.4 cal. ka. BP, which is consistent with previous work charting grounding line and ice shelf retreat to the coast, and open marine conditions in Nioghalvfjerdsbrae. Ice shelf retreat followed a period of enhanced atmospheric and ocean warming in the Early Holocene. Based on our detailed sedimentological, microfaunal and biomarker evidence the ice shelf reformed at Blåsø after 4.4 cal. ka BP, reaching a thickness similar to present by 4.0 cal. ka BP. Reformation of the ice shelf coincides with decreasing atmospheric temperatures, increased dominance of Polar Water, a reduction in Atlantic Water and near) perennial sea-ice cover on the adjacent continental shelf. Together with available climate archives our data indicate that 79°N ice shelf is susceptible to collapse when mean atmospheric and ocean temperatures are ~2°C warmer than present, which could be achieved by the middle of this century under 40 some climate model scenarios. Finally, the presence of 'marine' markers in the uppermost part of the Blåsø sediment cores could record modern ice shelf thinning, although the significance and precise timing of these changes requires further work. [ABSTRACT FROM AUTHOR]

The teaching roles, knowledge, beliefs, and broad guiding principles of two exemplary high school science teachers are discussed. A method to help other teachers reflect on their teaching is suggested.

High school students can learn about polymer chemistry through research using household clingfilm. They can compare the stress and strain properties of various wraps when they contain plasticizers, and also after plasticizers have been removed by oven heating. Knowledge of the relationship between materials' molecular structure and observed properties is strengthened by such studies.

The initiation and evolution of the Cordilleran Ice Sheet is relatively poorly constrained. International Ocean Discovery Program (IODP) Expedition 341 recovered marine sediments at Site U1417 in the Gulf of Alaska (GOA). Here we present alkenone-derived sea surface temperature (SST) analyses alongside ice rafted debris (IRD), pollen, terrigenous and marine organic matter (OM) inputs to the GOA through the late Pliocene and early Pleistocene. The first IRD contribution from tidewater glaciers in southwest Alaska is recorded at 2.9 Ma, indicating that the Cordilleran ice sheet extent increased in the late Pliocene. A higher occurrence of IRD and higher sedimentation rates in the GOA during the early Pleistocene, at 2.5 Ma, occur in synchrony with SSTs warming on the order of 1 °C relative to the Pliocene. All records show a high degree of variability in the early Pleistocene, indicating highly efficient ocean-climate-ice interactions through warm SST-ocean evaporation-orographic precipitation-ice growth mechanisms. A climatic shift towards ocean circulation in the subarctic Pacific similar to the pattern observed during negative Pacific Decadal Oscillation (PDO) conditions today appears to be a necessary pre-requisite to develop the Cordilleran glaciation and increase moisture supply to the subarctic Pacific. The drop in atmospheric CO2 concentrations since 2.8 Ma is suggested as one of the main forcing mechanisms driving the Cordilleran glaciation. [ABSTRACT FROM AUTHOR]

One of the largest uncertainties related to future projections of sea-level rise is the influence of ice sheets: their retreat, glacio-isostatic adjustment, and relative sea-level changes. Past ice sheet behavior and relative sea-level changes provide important analogues of how contemporary systems may respond to climate change. The presence of the British and Irish Ice Sheet and the Minch Ice Stream during the Last Glacial Maximum makes the northwest of Scotland an ideal study area to provide new constraints on relative sea-level limits and changes. 25 samples were collected for OSL dating from raised shorelines at elevations up to 20 m.a.s.l, along the coast from the Isle of Skye to Ullapool. Quartz separates were extracted with standard procedures and samples were dated with the SAR method [1]. Quartz samples investigated to date show favorable luminescence properties. OSL signals are on the order of 10,000 cts/0.4s after irradiation with 10 Gy (3mm aliquots). Preheat temperatures, as determined with plateau tests and dose recovery tests, are in the range of 180°C - 220°C. Recuperation values are well below 5% and recycling ratios are in the range 0.9 - 1.1. Dose recovery tests resulted in deviations of less than 10% for reliable aliquots. We will discuss further luminescence properties such as sunlight resetting and differences between samples from different sites. Finally, we will present ages for selected sites and their correlation with shoreline elevation. [ABSTRACT FROM AUTHOR]