ALBERT

Description: Die Bundesregierung gibt in ihrer Energiestrategie vor, dass die regenerativen Energien massiv ausgebaut werden, so dass sie eine tragende Säule der Energieversorgung darstellen und, um so den Ausstoß von CO2 reduzieren. Zu einer entsprechenden Empfehlung ist auch die Ethik- Kommission „Sichere Energieversorgung“ gekommen und konstatiert, dass saisonale Energiespeicher unter Nutzung von Wasserstoff oder Methan langfristig notwendig werden. Die hier vorgestellte, erweiterte „Power-to-Gas-to-Power“-Technologie (PGP, Abbildung) beruht auf der Erzeugung von Wasserstoff aus regenerativen Energien und daraus produziertem Methan unter Einsatz von im Kreislauf geführtem Kohlenstoffdioxid. Beide Gase werden in zwei beieinander lokalisierten, kombinierten Untergrundspeichern vorgehalten. Bei Energiebedarf wird Methan vor Ort in einem Gas-und Dampfturbinenkraftwerk umgesetzt, Kohlenstoffdioxid abgetrennt und emissionsneutral wieder in den Untergrundspeicher verbracht. Für die Bestimmung des notwendigen Energieeinsatzes beim Betrieb der CO2- und CH4-Untergrundspeicher wurden diese zunächst mit Hilfe numerischer Simulationen untersucht, um die Druckdynamik im Speicher während der Ein- und Ausspeicherung im Jahreszyklus zu bestimmen (Streibel et al. 2013). Die Rechnungen dienten als Grundlage, um den Energieeinsatz bei der Einspeisung der Gase in die jeweiligen Untergrundspeicher unter Berücksichtigung der spezifischen, temperatur- und druckabhängigen Eigenschaften von CH4 und CO2 zu berechnen. Unter Berücksichtigung aller Einzelschritte berechnet sich ein Gesamtwirkungsgrad von 27,7 % (Streibel et al. 2013) und Stromgestehungskosten von insgesamt 20,43 Eurocent/kWh (Kühn et al. 2013). Obwohl der Wirkungsgrad geringer als jener von Pump- und Druckluftspeichern ist, sind die resultierenden Kosten auf gleichem Niveau und damit konkurrenzfähig.

Description: WOR 1 provided a panoptic overview. The following report (WOR 2), the second in the series, focuses on the future of fish and their exploitation. Fish have always been a vital source of life for mankind – not only as a food. Fish continue to be essential to the daily diet of people in most regions of the world. At the same time fisheries provide a livelihood to entire coastal regions and still have great economic clout. All this, however, is in jeopardy and is coming under close scrutiny. Fish stocks are declining worldwide, entire marine regions are overfished and some species are already red-listed.

Description: Circumpolar permafrost soils store about half of the global soil organic carbon pool. These huge amounts of organic matter (OM) could accumulate due to low temperatures and water saturated soil conditions over the course of millennia. Currently most of this OM remains frozen and therefore does not take part in the active carbon cycle, making permafrost soils a globally important carbon sink. Over the last decades mean annual air temperatures in the Arctic increased stronger than the global mean and this trend is projected to continue. As a result the permafrost carbon pool is under climate pressure possibly creating a positive climate feedback due to the thaw-induced release of greenhouse gases to the atmosphere. Arctic warming will lead to increased annual permafrost thaw depths and Arctic river runoff likely resulting in enhanced mobilization and export of old, previously frozen soil-derived OM. Consequently, the great arctic rivers play an important role in global biogeochemical cycles by connecting the large permafrost carbon pool of their hinterlands with the arctic shelf seas and the Arctic Ocean. The first part of this thesis deals with particulate organic matter (POM) from the Lena Delta and adjacent Buor Khaya Bay. The Lena River in central Siberia is one of the major pathways translocating terrestrial OM from its southernmost reaches near Lake Baikal to the coastal zone of the Laptev Sea. The permafrost soils from the Lena catchment area store huge amounts of pre-aged OM, which is expected to be remobilized due to climate warming. To characterize the composition and vegetation sources of OM discharged by the Lena River, the lignin phenol and carbon isotopic composition (δ13C and Δ14C) in total suspended matter (TSM) from surface waters, surface sediments from the Buor Khaya Bay along with soils from the Lena Delta’s first (Holocene) and third terraces (Pleistocene ice complex) were analyzed. The lignin compositions of these samples are consistent with inputs of OM from non-woody angiosperm sources mixed with organic matter derived from woody gymnosperm sources. A simple linear mixing model based on the lignin phenol distributions indicates organic matter in TSM samples from the delta and Buor Khaya Bay surface sediments contain comparable contributions from gymnosperm sources, which are primarily from the taiga forests south of the delta, and angiosperm material typical for tundra vegetation. Considering the small area covered by tundra (~12% of total catchment), the input of tundra-derived OM input is substantial and likely to increase in a warming Arctic. Radiocarbon compositions (Δ14C) of bulk OM in Lena River TSM samples varied from –55 to –391‰, translating into 14C ages of 395 to 3920 years BP. Using δ13C compositions to estimate the fraction of phytoplankton-derived OM and assuming that this material has a modern 14C signature, we inferred the Δ14C compositions of terrigenous OM in TSM exported by the Lena River to range between –190 and –700‰. Such variability in the ages of terrigenous OM (i.e. 1640 to 9720 14C years BP) reflects the heterogeneous composition and residence time of OM in the Lena River catchment soils (Holocene to Pleistocene ages). Lignin phenol and Δ14C compositions of surface sediments from the adjacent Buor Khaya Bay suggest that terrestrial OM deposited there is older and more degraded than materials present in river particles and catchment soils. Stronger diagenetic alteration in Lena Delta TSM and marine sediments relative to soils may reflect degradation of more labile components during permafrost thawing and transport. Despite the high natural heterogeneity in catchment soils, the lignin biomarker compositions and radiocarbon ages of terrestrial OM exported by the Lena River reflect catchment characteristics such as vegetation and soil type. Climate warming related changes in the Lena River catchment may be detectable in changing lignin biomarker composition, diagenetic alteration, and radiocarbon age. The second part of this thesis investigates past permafrost dynamics and the possible permafrost/wetland climate feedback during the last deglaciation and Early Holocene. The Amur hinterland in East Siberia was most likely characterized by extensive permafrost during the last glacial maximum and is today permafrost-free with the exception of small areas in the northern reaches of the catchment. The organic matter flux of the Amur River into its receiving basin, the Okhotsk Sea, was reconstructed for the last 16,000 years in a high-resolution AMS 14C-dated sediment core from the Sakhalin continental margin, based on organic geochemical multi-proxy data and compound-specific radiocarbon dating of n-alkanoic acids. Within the deglacial discharge maximum of organic matter to the Okhotsk Sea, two peaks of organic matter release episodes; the first occurring during the Bølling-Allerød warm phase, and the second, larger one after Termination Ib in the earliest Preboreal could be identified. The results highlight the sensitivity of the Amur drainage basin’s carbon reservoir to rapid deglacial temperature and precipitation changes. It is hypothesized that large amounts of carbon were activated upon deglacial permafrost thawing within this southernmost Siberian large catchment and quickly transferred to the oceanic carbon reservoir via riverine freshwater transport into the Okhotsk Sea and the North Pacific.

Description: Heavy rainfall and flooding associated with tropical cyclones (TCs) are responsible for a large number of fatalities and economic damage worldwide. Despite their large socio-economic impacts, research into heavy rainfall and flooding associated with TCs has received limited attention to date, and still represents a major challenge. Our capability to adapt to future changesin heavy rainfall and flooding associated with TCs is inextricably linked to and informed by ourunderstanding of the sensitivity of TC rainfall to likely future forcing mechanisms. Here we use a set of idealized high-resolution atmospheric model experiments produced as part of the U.S. CLIVAR Hurricane Working Group activity to examine TC response to idealized global-scale perturbations: the doubling of CO2, uniform 2K increases in global sea surface temperature(SST), and their combined impact. As a preliminary but key step, daily rainfall patterns ofcomposite TCs within climate model outputs are first compared and contrasted to the observational records. To assess similarities and differences across different regions in response to the warming scenarios, analyses are performed at the global and hemispheric scales and in six global TC ocean basins. The results indicate a reduction in TC daily precipitation rates in the doubling CO2 scenario (on the order of 5% globally), and an increase in TC rainfall rates associated with a uniform increase of 2K in SST (both alone and in combination with CO2 doubling; on the order of 10-20% globally).

Description: Published

Description: 4622–4641

Description: 4A. Clima e Oceani

Description: JCR Journal

Description: open