ALBERT

Description: The emission rates of eight volatile halogenated compounds by three tropical brown seaweed species collected from Cape Rachado, west coast Peninsular Malaysia, under different irradiances have been determined. A purge-and-trap sample preparation system with a gas chromatograph and mass-selective detector was used to measure a suite of halocarbons released by Sargassum binderi Sonder ex J. Agardh, Padina australis Hauck, and Turbinaria conoides (J. Agardh) Kützing. All species are widely distributed in Peninsular Malaysia, with S. binderi a dominant seaweed species at our survey site. Release of few halocarbons was found to be influenced by irradiance. Correlations were also observed between emission of certain halocarbons with photosynthetic activity, especially bromo-and iodinated compounds (0.6 〈 r 〈0.9; p 〈 0.01) suggesting that environmental factors such as light can affect the release of these volatile halogenated compounds by the seaweeds into the atmosphere. Compared with temperate and polar brown seaweeds, tropical species, such as T. conoides, may emit higher levels of bromoform, CHBr3, and other halocarbons. It is therefore important to investigate the contribution of tropical seaweeds towards the local atmospheric composition of halocarbons.

Description: We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize themechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding.

Description: The Cadamosto Seamount is an unusual volcanic centre from Cape Verde, characterised by dominantly evolved volcanics, in contrast to the typically mafic volcanic centres at Cape Verde that exhibit only minor volumes of evolved volcanics. The magmatic evolution of Cadamosto Seamount is investigated to quantify the role of magma-crust interaction and thus provide a perspective on evolved end-member volcanism of Cape Verde. The preservation of mantle source signatures by Nd–Pb isotopes despite extensive magmatic differentiation provides new insights into the spatial distribution of mantle heterogeneity in the Cape Verde archipelago. Magmatic differentiation from nephelinite to phonolite involves fractional crystallisation of clinopyroxene, titanite, apatite, biotite and feldspathoids, with extensive feldspathoid accumulation being recorded in some evolved samples. Clinopyroxene crystallisation pressures of 0.38–0.17 GPa for the nephelinites constrain this extensive fractional crystallisation to the oceanic lithosphere, where no crustal assimilants or rafts of subcontinental lithospheric mantle are available. In turn, magma-crust interaction has influenced the Sr, O and S isotopes of the groundmass and late crystallising feldspathoids, which formed at shallow crustal depths reflecting the availability of oceanic sediments and anhydrite precipitated in the ocean crust. The Nd–Pb isotopes have not been affected by these processes of magma-crust interaction and hence preserve the mantle source signature. The Cadamosto Seamount samples have high 206Pb/204Pb (〉19.5), high εNd (+6 to +7) and negative Δ8/4Pb, showing affinity with the northern Cape Verde islands as opposed to the adjacent southern islands. Hence, the Cadamosto Seamount in the west is located spatially beyond the EM1-like component found further east. This heterogeneity is not encountered in the oceanic lithosphere beneath the Cadamosto Seamount despite greater extents of fractional crystallisation at oceanic lithospheric depths than the islands of Fogo and Santiago. Our data provide new evidence for the complex geometry of the chemically zoned Cape Verde mantle source.