A new regional climate model for POLAR-CORDEX : evaluation of a 30-year hindcast with COSMO-CLM2 over Antarctica

Continent-wide climate information over the Antarctic Ice Sheet (AIS) is important to obtain accurate information of present climate and reduce uncertainties of the ice sheet mass balance response and resulting global sea level rise to future climate change. In this study, the COSMO-CLM2 Regional Climate Model is applied over the AIS and adapted for the specific meteorological and climatological conditions of the region. A 30-year hindcast was performed and evaluated against observational records consisting of long-term ground-based meteorological observations, automatic weather stations, radiosoundings, satellite records, stake measurements and ice cores. Reasonable agreement regarding the surface and upper-air climate is achieved by the COSMO-CLM2 model, comparable to the performance of other state-of-the-art climate models over the AIS. Meteorological variability of the surface climate is adequately simulated, and biases in the radiation and surface mass balance are small. The presented model therefore contributes as a new member to the COordinated Regional Downscaling EXperiment project over the AIS (POLAR-CORDEX) and the CORDEX-CORE initiative

Reconciling the surface temperature–surface mass balance relationship in models and ice cores in Antarctica over the last 2 centuries

Ice cores are an important record of the past surface mass balance (SMB) of ice sheets, with SMB mitigating the ice sheets' sea level impact over the recent decades. For the Antarctic Ice Sheet (AIS), SMB is dominated by large-scale atmospheric circulation, which collects warm moist air from further north and releases it in the form of snow as widespread accumulation or focused atmospheric rivers on the continent. This suggests that the snow deposited at the surface of the AIS should record strongly coupled SMB and surface air temperature (SAT) variations. Ice cores use δ18O as a proxy for SAT as they do not record SAT directly. Here, using isotope-enabled global climate models and the RACMO2.3 regional climate model, we calculate positive SMB–SAT and SMB–δ18O annual correlations over ∼90 % of the AIS. The high spatial resolution of the RACMO2.3 model allows us to highlight a number of areas where SMB and SAT are not correlated, and we show that wind-driven processes acting locally, such as foehn and katabatic effects, can overwhelm the large-scale atmospheric contribution in SMB and SAT responsible for the positive SMB–SAT annual correlations. We focus in particular on Dronning Maud Land, East Antarctica, where the ice promontories clearly show these wind-induced effects. However, using the PAGES2k ice core compilations of SMB and δ18O of Thomas et al. (2017) and Stenni et al. (2017), we obtain a weak annual correlation, on the order of 0.1, between SMB and δ18O over the past ∼150 years. We obtain an equivalently weak annual correlation between ice core SMB and the SAT reconstruction of Nicolas and Bromwich (2014) over the past ∼50 years, although the ice core sites are not spatially co-located with the areas displaying a low SMB–SAT annual correlation in the models. To resolve the discrepancy between the measured and modeled signals, we show that averaging the ice core records in close spatial proximity increases their SMB–SAT annual correlation. This increase shows that the weak measured annual correlation partly results from random noise present in the ice core records, but the change is not large enough to match the annual correlation calculated in the models. Our results thus indicate a positive correlation between SAT and SMB in models and ice core reconstructions but with a weaker value in observations that may be due to missing processes in models or some systematic biases in ice core data that are not removed by a simple average

De Noordzee: een waardevol archief onder water. Meer dan 100 jaar onderzoek van strandvondsten en vondsten uit zee in België: een overzicht

De Noordzee kan beschouwd worden als een waardevol en speciaal archief, met heel wat interessante informatie over het verleden. De zone beneden de laagwaterlijn behoort tot het domein van de subtidale archeologie of de archeologie van het subgetijdengebied van de Noordzee. De zone tussen de hoog- en de laagwaterlijn behoort tot de intertidale archeologie of de archeologie van het intergetijdengebied van de Noordzee. In het eerste deel van deze studie wordt kort de geschiedenis van het onderzoek in deze beide zones geschetst. Daarna wordt in een tweede deel een chronologisch overzicht gegeven van de resultaten van het onderzoek en dit vanaf het ontstaan van de archeologie als wetenschappelijke discipline. In dit tweede deel wordt ook een klein aantal tot nu toe ongepubliceerde vondsten opgenomen van buiten het Belgische deel van de Noordzee. De reden hiervoor is zowel pragmatisch als inhoudelijk. Enerzijds worden deze vondsten geregistreerd samen met de andere vondsten, ze bevinden zich immers samen in de bestudeerde collecties. Anderzijds dragen ze ook inhoudelijk bij tot een beter inzicht in de genese van het hele zuidelijke Noordzeegebied, waarvan de zone onder Belgisch toezicht deel uitmaakt. Verder dienen in dit tweede deel ook een aantal vraagstellingen en onderzoeksstrategieën als basis voor de globale discussie in het derde deel van deze bijdrage. De bijdrage wordt ten slotte afgesloten met een zo volledig mogelijke bibliografie over het onderzoek in het Belgische deel van de Noordzee inclusief de stranden

From vocational training to education: the development of a no-frontiers education policy for Europe?

This article focuses on developments towards an EU educational policy. Education was not included as one of the Community competencies in the Treaty of Rome. The first half of the article analyses the way that the European Court of Justice and the Commission of the European Communities between them managed to develop a series of substantial Community programmes out of Article 128 on vocational training. The second half of the article discusses educational developments in the community following the Treaty on European Union and the Treaty of Amsterdam. Whilst the legal competence of the community now includes education, the author's argument is that the inclusion of an educational competence will not result in further developments to mirror those in the years before the Treaty on Europe</p

Structural and Luminescence Properties of Silica-Based Hybrids Containing New Silylated-Diketonato Europium(III) Complex

A new betadiketonate ligand displaying a trimethoxysilyl group as grafting function and a diketone moiety as complexing site (TTA-Si = 4,4,4-trifluoro-2-(3-trimethoxysilyl)propyl)-1-3-butanedione (C4H3S)COCH[(CH2)3Si(OCH3)3]COCF3) and its highly luminescent europium(III) complex [Eu(TTA-Si)3] have been synthesized and fully characterized. Luminescent silica-based hybrids have been prepared as well with this new complex grafted on the surface of dense silica nanoparticles (28 (+/-3 nm) or on mesoporous silica particles. The covalent bonding of Eu(TTA-Si)3 inside the core of uniform silica nanoparticles (40 (+/- 5 nm) was also achieved. Luminescence properties are discussed in relation to the europium chemical environment involved in each of the three hybrids. The general methodology proposed allowed high grafting ratios and overcame chelate release and tendency to agglomeration, and it could be applied to any silica matrix (in the core or at the surface, nanosized or not, dense or mesoporous) and therefore numerous applications such as luminescent markers and luminophors could be foreseen

Drifting snow measurements on the Greenland Ice Sheet and their application for model evaluation

This paper presents autonomous drifting snow observations performed on the Greenland Ice Sheet in the fall of 2012. High-frequency snow particle counter (SPC) observations at ~ 1 m above the surface provided drifting snow number fluxes and size distributions; these were combined with meteorological observations at six levels. We identify two types of drifting snow events: katabatic events are relatively cold and dry, with prevalent winds from the southeast, whereas synoptic events are short lived, warm and wet. Precipitating snow during synoptic events disturbs the drifting snow measurements. Output of the regional atmospheric climate model RACMO2, which includes the drifting snow routine PIEKTUK-B, agrees well with the observed near-surface climate at the site, as well as with the frequency and timing of drifting snow events. Direct comparisons with the SPC observations at 1 m reveal that the model overestimates the horizontal snow transport at this level, which can be related to an overestimation of saltation and the typical size of drifting snow particles

Ice core evidence for a 20th century increase in surface mass balance in coastal Dronning Maud Land, East Antarctica

Ice cores provide temporal records of surface mass balance (SMB). Coastal areas of Antarctica have relatively high and variable SMB, but are under-represented in records spanning more than 100 years. Here we present SMB reconstruction from a 120 m-long ice core drilled in 2012 on the Derwael Ice Rise, coastal Dronning Maud Land, East Antarctica. Water stable isotope (δ18O and δD) stratigraphy is supplemented by discontinuous major ion profiles and continuous electrical conductivity measurements. The base of the ice core is dated to AD 1759 ± 16, providing a climate proxy for the past  ∼ 250 years. The core's annual layer thickness history is combined with its gravimetric density profile to reconstruct the site's SMB history, corrected for the influence of ice deformation. The mean SMB for the core's entire history is 0.47 ± 0.02 m water equivalent (w.e.) a−1. The time series of reconstructed annual SMB shows high variability, but a general increase beginning in the 20th century. This increase is particularly marked during the last 50 years (1962–2011), which yields mean SMB of 0.61 ± 0.01 m w.e. a−1. This trend is compared with other reported SMB data in Antarctica, generally showing a high spatial variability. Output of the fully coupled Community Earth System Model (CESM) suggests that, although atmospheric circulation is the main factor influencing SMB, variability in sea surface temperatures and sea ice cover in the precipitation source region also explain part of the variability in SMB. Local snow redistribution can also influence interannual variability but is unlikely to influence long-term trends significantly. This is the first record from a coastal ice core in East Antarctica to show an increase in SMB beginning in the early 20th century and particularly marked during the last 50 years

Meltwater produced by wind–albedo interaction stored in an East Antarctic ice shelf

Surface melt and subsequent firn air depletion can ultimately lead to disintegration of Antarctic ice shelves1,2 causing grounded glaciers to accelerate3 and sea level to rise. In the Antarctic Peninsula, foehn winds enhance melting near the grounding line4, which in the recent past has led to the disintegration of the most northerly ice shelves5,6. Here, we provide observational and model evidence that this process also occurs over an East Antarctic ice shelf, where meltwaterinduced firn air depletion is found in the grounding zone. Unlike the Antarctic Peninsula, where foehn events originate from episodic interaction of the circumpolar westerlies with the topography, in coastal East Antarctica high temperatures are caused by persistent katabatic winds originating from the ice sheet’s interior. Katabatic winds warm and mix the air as it flows downward and cause widespread snow erosion, explaining >3 K higher near-surface temperatures in summer and surface melt doubling in the grounding zone compared with its surroundings. Additionally, these winds expose blue ice and firn with lower surface albedo, further enhancing melt. The in situ observation of supraglacial flow and englacial storage of meltwater suggests that ice-shelf grounding zones in East Antarctica, like their Antarctic Peninsula counterparts, are vulnerable to hydrofracturing7