Multiple Geronimus transformations

We consider multiple Geronimus transformations and show that they lead to discrete (non-diagonal) Sobolev type inner products. Moreover, it is shown that every discrete Sobolev inner product can be obtained as a multiple Geronimus transformation. A connection with Geronimus spectral transformations for matrix orthogonal polynomials is also considered.The work of Francisco Marcellán has been supported by Dirección General de Investigación, Desarrollo e Innovación, Ministerio de Economía y Competitividad of Spain, grant MTM2012-36732-C03-01

Northern Eurasia Future Initiative (NEFI): facing the challenges and pathways of global change in the 21st century

During the past several decades, the Earth system has changed significantly, especially across Northern Eurasia. Changes in the socio-economic conditions of the larger countries in the region have also resulted in a variety of regional environmental changes that can have global consequences. The Northern Eurasia Future Initiative (NEFI) has been designed as an essential continuation of the Northern Eurasia Earth Science Partnership Initiative (NEESPI), which was launched in 2004. NEESPI sought to elucidate all aspects of ongoing environmental change, to inform societies and, thus, to better prepare societies for future developments. A key principle of NEFI is that these developments must now be secured through science-based strategies co-designed with regional decision makers to lead their societies to prosperity in the face of environmental and institutional challenges. NEESPI scientific research, data, and models have created a solid knowledge base to support the NEFI program. This paper presents the NEFI research vision consensus based on that knowledge. It provides the reader with samples of recent accomplishments in regional studies and formulates new NEFI science questions. To address these questions, nine research foci are identified and their selections are briefly justified. These foci include: warming of the Arctic; changing frequency, pattern, and intensity of extreme and inclement environmental conditions; retreat of the cryosphere; changes in terrestrial water cycles; changes in the biosphere; pressures on land-use; changes in infrastructure; societal actions in response to environmental change; and quantification of Northern Eurasia's role in the global Earth system. Powerful feedbacks between the Earth and human systems in Northern Eurasia (e.g., mega-fires, droughts, depletion of the cryosphere essential for water supply, retreat of sea ice) result from past and current human activities (e.g., large scale water withdrawals, land use and governance change) and potentially restrict or provide new opportunities for future human activities. Therefore, we propose that Integrated Assessment Models are needed as the final stage of global change assessment. The overarching goal of this NEFI modeling effort will enable evaluation of economic decisions in response to changing environmental conditions and justification of mitigation and adaptation efforts

Vegetation and climate changes on the northern Taymyr, Russia during the Upper Pleistocene and Holocene reconstructed from pollen records

Pollen data from a Levinson-Lessing Lake sediment core (74°28'N, 98°38'E) and Cape Sabler,Taymyr Lake permafrost sequences (74°33'N, 100°32'E) reveal substantial environmental changeson the northern Taymyr Peninsula during the last c. 32 000 14C years. The continuous recordsconfirm that a scarce steppe-like vegetation with Poaceae, Artemisia, and Cyperaceae dominatedc. 32 000-10 300 14C yr BP, while tundra-like vegetation with Oxyria, Ranunculaceae andCaryophyllaceae grew in wetter areas. The coldest interval occurred c. 18 000 yr BP. Lateglacialpollen data show several warming events followed by a climate deterioration c. 10 500 14C yr BP,which may correspond with the Younger Dryas. The Late Pleistocene/Holocene transition,c. 10 300-10 000 14C yr BP, is characterized by a change from the herb-dominated vegetation toshrubby tundra with Betula sect. Nanae and Salix. Alnus fruticosa arrived locally c. 9000-8500 14Cyr BP and disappeared c. 4000-3500 14C yr BP. Communities of Betula sect. Nanae, broadlydistributed at c. 10,000-3500 14C yr BP, almost disappeared when vegetation became similar tothe modern herb tundra after 3500-3000 14C yr BP. Quantitative climate reconstructions showLast Glacial Maximum summer temperature about 4°C below present and Preboreal (c. 10 00014C yr BP) temperature 2-4°C above present. Maximum summer temperature occurred between10 000 and 5500 14C yr BP; later summers were similar to present or slightly warmer

Late glacial to Holocene environmental dynamics of the terrestrial Arctic new records from thermokarst deposits along the Dmitry Laptev Strait (NE Siberia)

The palaeo-landscape and environmental history during the last glacial-interglacial transition was studied in a broader regional context by comparing permafrost sequences from the northern and the southern coasts of the Dmitry Laptev Strait (East Siberian Sea) on Bolshoy Lyakhovsky Island (73°17′N, 141°20′E) and on the Oyogos Yar coast (72°36'N, 143°36'E).Both coastal exposures show the same general stratigraphy pointing to similar landscape and environmental dynamics which were reconstructed using cryolithological, sedimentological and micro-palaeontological (i.e. pollen, freshwater ostracods) methods as well as stable isotope data from ice wedges.The late Glacial and Holocene permafrost records of both coastal sections are subdivided into three horizons that are of taberal (thawed and refrozen), lacustrine, and boggy origin.In both sections, the lowermost horizons consist of taberal deposits of the former late Pleistocene Ice Complex (dated between 46.6 and 36.6 14C kyr BP) which are composed of sandy silt with peat lenses and thaw signs (whitish laminations). The ice content is generally low and the cryostructures are lens-like reticulated or layered, typical for refrozen sediments. The pollen data from the taberal horizons point to a Middle Weichselian interstadial vegetation. Ostracod shells are rare.The taberal horizon is discordantly covered by a lacustrine horizon of late Glacial age (dated between 14.8 and 12.5 14C kyr BP). Its lowermost part is composed of cryoturbated peaty palaeosols in both sections. The overlying lacustrine facies is structured by alternating beds of clayish silts and plant detritus layers which contain numerous mollusc shells, ostracods, and wood fragments. The cryostructure is lens-like or lens-like layered and epigenetic roots of ice wedges are common within the lacustrine horizons. Pollen records are in good accordance with Allerød to Younger Dryas ages indicating a grass-sedge tundra dominated vegetation. The ostracod records point to stable aquatic conditions during the late Glacial where the high numbers and diverse assemblages were found. Thus, thermokarst development and lake formation started some time before the Holocene. The uppermost horizons accumulated under subaerial conditions in a boggy polygonal tundra environment from about 7.5 to 4.0 14C kyr BP at the Bolshoy Lyakhovsky section and between about 10.0 and 3.3 14C kyr BP at the Oyogos Yar section. However, the late Holocene deposits discordantly cover the underlying early Holocene sediments.Numerous peat inclusions or single peat layers were found in a sandy silt matrix with ice bands and a lens-like cryostructure between single bands which indicate syngenetic freezing of the sediments. Stable isotope signatures of ice wedges syngenetically formed in boggy deposits clearly differ from isotope composition of Weichselian ice wedges, pointing to warmer conditions during the Holocene. However, a notable variability and a clear warming trend occurred during the last millennium. An early Holocene shrubby tundra vegetation is reconstructed from the pollen spectra, whereas the late Holocene pollen spectra indicate a shift to modern wetland tundra vegetation. The early Holocene ostracod assemblages are sparse and low diverse.The multi-proxy palaeoenvironmental record of the last glacial- interglacial transition indicates a general pattern of regional landscape development according to climatic changes. Evidence of the three landscape development stages was obtained, including (1) thermokarst-induced formation of basins, (2) accumulation of lacustrine sequences, and (3) transformation of lake-dominated areas into polygonal tundra. The stages are considered to be of stratigraphical significance