852 resultados para Zatulovskaja, Irina
Resumo:
Samoylov Island is centrally located within the Lena River Delta at 72° N, 126° E and lies within the Siberian zone of continuous permafrost. The landscape on Samoylov Island consists mainly of late Holocene river terraces with polygonal tundra, ponds and lakes, and an active floodplain. The island has been the focus of numerous multidisciplinary studies since 1993, which have focused on climate, land cover, ecology, hydrology, permafrost and limnology. This paper aims to provide a framework for future studies by describing the characteristics of the island's meteorological parameters (temperature, radiation and snow cover), soil temperature, and soil moisture. The land surface characteristics have been described using high resolution aerial images in combination with data from ground-based observations. Of note is that deeper permafrost temperatures have increased between 0.3 to 1.3 °C over the last five years. However, no clear warming of air and active layer temperatures is detected since 1998, though winter air temperatures during recent years have not been as cold as in earlier years.
Resumo:
Owing to their important roles in biogeochemical cycles, phytoplankton functional types (PFTs) have been the aim of an increasing number of ocean color algorithms. Yet, none of the existing methods are based on phytoplankton carbon (C) biomass, which is a fundamental biogeochemical and ecological variable and the "unit of accounting" in Earth system models. We present a novel bio-optical algorithm to retrieve size-partitioned phytoplankton carbon from ocean color satellite data. The algorithm is based on existing methods to estimate particle volume from a power-law particle size distribution (PSD). Volume is converted to carbon concentrations using a compilation of allometric relationships. We quantify absolute and fractional biomass in three PFTs based on size - picophytoplankton (0.5-2 µm in diameter), nanophytoplankton (2-20 µm) and microphytoplankton (20-50 µm). The mean spatial distributions of total phytoplankton C biomass and individual PFTs, derived from global SeaWiFS monthly ocean color data, are consistent with current understanding of oceanic ecosystems, i.e., oligotrophic regions are characterized by low biomass and dominance of picoplankton, whereas eutrophic regions have high biomass to which nanoplankton and microplankton contribute relatively larger fractions. Global climatological, spatially integrated phytoplankton carbon biomass standing stock estimates using our PSD-based approach yield - 0.25 Gt of C, consistent with analogous estimates from two other ocean color algorithms and several state-of-the-art Earth system models. Satisfactory in situ closure observed between PSD and POC measurements lends support to the theoretical basis of the PSD-based algorithm. Uncertainty budget analyses indicate that absolute carbon concentration uncertainties are driven by the PSD parameter No which determines particle number concentration to first order, while uncertainties in PFTs' fractional contributions to total C biomass are mostly due to the allometric coefficients. The C algorithm presented here, which is not empirically constrained a priori, partitions biomass in size classes and introduces improvement over the assumptions of the other approaches. However, the range of phytoplankton C biomass spatial variability globally is larger than estimated by any other models considered here, which suggests an empirical correction to the No parameter is needed, based on PSD validation statistics. These corrected absolute carbon biomass concentrations validate well against in situ POC observations.
Resumo:
It is expected that the calcification of foraminifera will be negatively affected by the ongoing acidification of the oceans. Compared to the open oceans, these organisms are subjected to much more adverse carbonate system conditions in coastal and estuarine environments such as the southwestern Baltic Sea, where benthic foraminifera are abundant. This study documents the seasonal changes of carbonate chemistry and the ensuing response of the foraminiferal community with bi-monthly resolution in Flensburg Fjord. In comparison to the surface pCO2, which is close to equilibrium with the atmosphere, we observed large seasonal fluctuations of pCO2 in the bottom and sediment pore waters. The sediment pore water pCO2 was constantly high during the entire year ranging from 1244 to 3324 µatm. Nevertheless, in contrast to the bottom water, sediment pore water was slightly supersaturated with respect to calcite as a consequence of higher alkalinity (AT) for most of the year. Foraminiferal assemblages were dominated by two calcareous species, Ammonia aomoriensis and Elphidium incertum, and the agglutinated Ammotium cassis. The one-year cycle was characterised by seasonal community shifts. Our results revealed that there is no dynamic response of foraminiferal population density and diversity to elevated sediment pore water pCO2. Surprisingly, the fluctuations of sediment pore water undersaturation (Omega calc) co-vary with the population densities of living Ammonia aomoriensis. Further, we observed that most of the tests of living calcifying foraminifera were intact. Only Ammonia aomorienis showed dissolution and recalcification structures on the tests, especially at undersaturated conditions. Therefore, the benthic community is subjected to high pCO2 and tolerates elevated levels as long as sediment pore water remains supersaturated. Model calculations inferred that increasing atmospheric CO2 concentrations will finally lead to a perennial undersaturation in sediment pore waters. Whereas benthic foraminifera indeed may cope with a high sediment pore water pCO2, the steady undersaturation of sediment pore waters would likely cause a significant higher mortality of the dominating Ammonia aomoriensis. This shift may eventually lead to changes in the benthic foraminiferal communities in Flensburg Fjord, as well as in other regions experiencing naturally undersaturated Omega calc levels.
Resumo:
The linguistic situation in Greek-speaking Cyprus has been traditionally described as a textbook case of diglossia à la Ferguson (1959) with Standard Modern Greek (SModGr) being labelled as the High variety and Cypriot Greek (CypGr), the regional ModGr variety of Cyprus, being labelled the Low variety (Arvaniti, 2011; Moschonas, 1996). More recently, however, it has been proposed that the linguistic repertoire available to speakers features an array of forms of CypGr, which is best described as a continuum ranging from basilectal to acrolectal varieties (Katsoyannou et al., 2006; Tsiplakou et al., 2006). The basilectal end encompasses low prestige varieties predominantly spoken in rural areas. The acrolectal end is occupied by the version of SModGr used in the public domain in Cyprus (Arvaniti, 2006/2010). SModGr is known to carry high prestige in Cyprus. Speakers of CypGr describe speakers of the standard as more attractive, more intelligent, more interesting and more educated than speakers of the Cypriot dialect (Papapavlou, 1998). In this paper, I explore the relation between SModGr and CypGr in a diasporic setting, namely, the Greek Cypriot community of London. The United Kingdom is home to a sizeable Greek Cypriot community, whose population is presently estimated to fall between 200,000 and 300,000 individuals (Christodoulou-Pipis, 1991; National Federation of Cypriots in the UK). Similarly to the Cyprus homeland, the members of the Greek Cypriot parikia (‘community’) share a rich linguistic repertoire, which, in addition to varieties of Greek, crucially includes English. As is often the case with diasporas, the parikia does not form a homogeneous speech community in that not all of its members have an equally good command of Greek or even English. Rather, different types of monolingual and bilingual speakers are found including a large number of heritage speakers in the sense of Benmamoun et al. (2013), Montrul (2008, 2015) and Polinsky & Kagan (2007). Twenty British-born heritage speakers of CypGr were interviewed on their attitudes towards the different varieties of Greek. Results indicate that the prestige relation between SModGr and CypGr that holds in Cyprus has been transplanted to the parikia. SModGr is widely perceived as the prestigious variety and is described in positive terms (‘correct’, ‘proper’). The use of CypGr, on the other hand, enjoys covert prestige: it is perceived as an index of solidarity and in-group membership but at the same time is also viewed by heritage speakers as reminiscent of the hardship and lack of education of the generation that brought CypGr to the UK. In certain cases, the use of CypGr by heritage speakers is actively discouraged by the first generation not only in the public domain but also in private domains such as the home. Active discouragement targets both lexical and grammatical variants that are traditionally associated with basilectal varieties of CypGr, and heritage language features, especially the adoption of morphologically adapted loanwords from English. References Arvaniti, Amalia. 2006/2010. Linguistic practices in Cyprus and the emergence of Cypriot Standard Greek. Mediterranean Language Review 17, 15–45. Benmamoun, Elabbas, Silvina Montrul & Maria Polinsky. 2013. Heritage languages and their speakers: opportunities and challenges for linguists. Theoretical Linguistics 39(3/4), 129–181. Christodoulou-Pipis, Irina. 1991. Greek Outside Greece: Language Use by Greek-Cypriots in Britain. Nicosia: Diaspora Books. Ferguson, Charles A. 1959. Diglossia. Word 15(2), 325–340. Katsoyannou, Marianna, Andreas Papapavlou, Pavlos Pavlou & Stavroula Tsiplakou. 2006. Didialektikes koinotites kai glossiko syneches: i periptosi tis kypriakis [Bidialectal communities and linguistic continuum: the case of Cypriot Greek]. In Mark Janse, Brian D. Joseph & Angela Ralli (eds.), Proceedings of the 2nd International Conference of Modern Greek Dialects and Linguistic Theory, Mytilene, Greece, 30 September – 3 October 2004, 156–171. Patras: University of Patras. Montrul, Silvina A. 2008. Incomplete Acquisition in Bilingualism: Re-examining the Age Factor. Amsterdam/Philadelphia: John Benjamins. Montrul, Silvina. 2015. The Acquisition of Heritage Languages. Cambridge: Cambridge University Press. Moschonas, Spiros. 1996. I glossiki dimorfia stin Kypro [Diglossia in Cyprus]. In “Ischyres” – “Astheneis” Glosses stin Evropaiki Enosi: Opseis tou glossikou igemonismou [“Strong” – “Weak” Languages in the European Union: Aspects of Linguistic Imperialism], 121–128. Thessaloniki: Kentro Ellinikis Glossas. Polinsky, Maria & Olga Kagan. 2007. Heritage languages: in the ‘wild’ and in the classroom. Languages and Linguistics Compass 1(5), 368–395. Tsiplakou, Stavroula, Andreas Papapavlou, Pavlos Pavlou & Marianna Katsoyannou. 2006. Levelling, koineization and their implications for bidialectism. In Frans L. Hinskens (Eds.), Language Variation – European Perspectives: Selected Papers from the Third International Conference on Language Variation in Europe (ICLaVE 3), Amsterdam, June 2005, 265–279. Amsterdam/Philadelphia: John Benjamins.
Resumo:
International migration sets in motion a range of significant transnational processes that connect countries and people. How migration interacts with development and how policies might promote and enhance such interactions have, since the turn of the millennium, gained attention on the international agenda. The recognition that transnational practices connect migrants and their families across sending and receiving societies forms part of this debate. The ways in which policy debate employs and understands transnational family ties nevertheless remain underexplored. This article sets out to discern the understandings of the family in two (often intermingled) debates concerned with transnational interactions: The largely state and policydriven discourse on the potential benefits of migration on economic development, and the largely academic transnational family literature focusing on issues of care and the micro-politics of gender and generation. Emphasizing the relation between diverse migration-development dynamics and specific family positions, we ask whether an analytical point of departure in respective transnational motherhood, fatherhood or childhood is linked to emphasizing certain outcomes. We conclude by sketching important strands of inclusions and exclusions of family matters in policy discourse and suggest ways to better integrate a transnational family perspective in global migration-development policy.