High resolution regional climate model simulations for Germany: Part II—projected climate changes

The projected climate change signals of a five-member high resolution ensemble, based on two global climate models (GCMs: ECHAM5 and CCCma3) and two regional climate models (RCMs: CLM and WRF) are analysed in this paper (Part II of a two part paper). In Part I the performance of the models for the control period are presented. The RCMs use a two nest procedure over Europe and Germany with a final spatial resolution of 7 km to downscale the GCM simulations for the present (1971–2000) and future A1B scenario (2021–2050) time periods. The ensemble was extended by earlier simulations with the RCM REMO (driven by ECHAM5, two realisations) at a slightly coarser resolution. The climate change signals are evaluated and tested for significance for mean values and the seasonal cycles of temperature and precipitation, as well as for the intensity distribution of precipitation and the numbers of dry days and dry periods. All GCMs project a significant warming over Europe on seasonal and annual scales and the projected warming of the GCMs is retained in both nests of the RCMs, however, with added small variations. The mean warming over Germany of all ensemble members for the fine nest is in the range of 0.8 and 1.3 K with an average of 1.1 K. For mean annual precipitation the climate change signal varies in the range of ?2 to 9 % over Germany within the ensemble. Changes in the number of wet days are projected in the range of ±4 % on the annual scale for the future time period. For the probability distribution of precipitation intensity, a decrease of lower intensities and an increase of moderate and higher intensities is projected by most ensemble members. For the mean values, the results indicate that the projected temperature change signal is caused mainly by the GCM and its initial condition (realisation), with little impact from the RCM. For precipitation, in addition, the RCM affects the climate change signal significantly.     

Testing a spatially distributed tracer‐aided runoff model in a snow‐influenced catchment: Effects of multicriteria calibration on streamwater ages

Integrating stable isotope tracers into rainfall‐runoff models allows investigation of water partitioning and direct estimation of travel times and water ages. Tracer data have valuable information content that can be used to constrain models and, in integration with hydrometric observations, test the conceptualization of catchment processes in model structure and parameterization. There is great potential in using tracer‐aided modelling in snow‐influenced catchments to improve understanding of these catchments' dynamics and sensitivity to environmental change. We used the spatially distributed tracer‐aided rainfall‐runoff (STARR) model to simulate the interactions between water storage, flux, and isotope dynamics in a snow‐influenced, long‐term monitored catchment in Ontario, Canada. Multiple realizations of the model were achieved using a combination of single and multiple objectives as calibration targets. Although good simulations of hydrometric targets such as discharge and snow water equivalent could be achieved by local calibration alone, adequate capture of the stream isotope dynamics was predicated on the inclusion of isotope data in the calibration. Parameter sensitivity was highest, and most local, for single calibration targets. With multiple calibration targets, key sensitive parameters were still identifiable in snow and runoff generation routines. Water ages derived from flux tracking subroutines in the model indicated a catchment where runoff is dominated by younger waters, particularly during spring snowmelt. However, resulting water ages were most sensitive to the partitioning of runoff sources from soil and groundwater sources, which was most realistically achieved when isotopes were included in the calibration. Given the paucity of studies where hydrological models explicitly incorporate tracers in snow‐influenced regions, this study using STARR is an important contribution to satisfactorily simulating snowpack dynamics and runoff generation processes, while simultaneously capturing stable isotope variability in snow‐influenced catchments.     

Observations of Lunar Transient Phenomena (LTP) in 1972 and 1973

A list of reports of Lunar Transient Phenomena (LTP) which have been observed in 1972 and 1973 by an international group of amateur astronomers is given. From 907 monitoring observations (1972: 526, 1973: 381) 92 LTP (74 reliable, 18 possible individual sightings) have been reported (1972: 52, 1973: 40) including parallel observations of the same event. The LTP were brightenings, shadings, flashes, colours, moving clouds and brightness diminutions of stars before occultations. 45 LTP events may be expected to be real in a catalogue of criteria for the reliability of observations. Sixteen events have been reported by several independent observers. A short examination of the temporal distributions of monitoring observations and recorded LTP is given.     

West African palaeosynoptic patterns at the last glacial maximum

Summary The composite method and an atmospheric moisture budget is applied to study the present synoptic summer situation in the West African Sahel. This allows the information of the synoptic scale flow systems at the last glacial maximum to be obtained. Relying on the results of general circulation models and of local geological findings the palaeosynoptic situation was found to consist of the same constituents as today's given pattern. In both time slices the strength of the midtropospheric African Easterly Jet determines the intensity and frequency of the Sahelian synoptic disturbances: the Easterly Waves and the Squall Lines. The glacial rainfall intensity of the Squall Lines, the most effective rain-bearing system of the Sahel, is calculated to be 2/3 of the modern one. Additionally, only half the number of Squall Lines propagated across the West African continent per summer month. Thus the glacial rainfall amount of the Sahel was roughly 30% of the value observed today.With 6 Figures     

Polymetallic Nodule Mining, Waste Disposal, and Species Extinction at the Abyssal Seafloor

The size of individual mining blocks for polymetallic nodule extraction seems to be rather small, not more than 100 km² in the French mining claim. Even when adding an additional resedimentation zone to the directly impacted area, the size of the affected seabed would remain below 200 km². We assume that even rare species in the abyss inhabit larger areas and propose discussions of the International Seabed Authority and other stakeholders for the different subregions on mining strategies from the perspective of exploitation versus species extinction and conservation. Although impacts of waste disposal at the abyssal seafloor are different from those of nodule mining, the 200 km² concept may also be applied.     

Spatial organization of groundwater dynamics and streamflow response from different hydropedological units in a montane catchment

Groundwater dynamics play an important role in runoff generation and hydrologic connectivity between hillslopes and streams. We monitored a network of 14 shallow groundwater (GW) wells in a 3.2 km² experimental catchment in the Scottish Highlands. Wells were placed in three contrasting landscape units with different hydropedological characteristics and different topographic positions relative to the stream network, encompassing a catena sequence from freely draining podzols on steeper hillslopes to increasingly thick peats (histosols) in the valley bottom riparian zone. GW dynamics were characterized by statistical analyses of water table fluctuations, estimation of variabilities in lag times and hysteresis response in relation to streamflow. The three landscape units had distinct storage–discharge relationships and threshold responses with a certain GW level above which lateral flow dominates. Steeper hillslopes with freely draining podzols were characterized by GW fluctuations of around 150 cm in the underlying drift. GW usually showed peak response up to several hours after stream flow. During persistent wet periods the water table remained in the soil profile for short spells and connected shallow flow paths in the near surface horizons to the lower hillslopes. In the peaty gleys in the lower foot slopes, GW was characterized by a water table generally within 20 cm of the soil surface, though at some locations this could fall to 50 cm in extreme dry periods. GW responses were usually a few hours prior to the stream responses. In riparian peats, the water table was also usually less than 20 cm deep and responded several hours before the stream. These riparian peat soils remain at, or very near saturation with near‐continuous GW–surface water connectivity. In contrast, the steeper slopes remain disconnected for prolonged periods and need large recharge events to overcome storage thresholds. GW responses vary seasonally, and landscape controls on the spatial organization of GW dynamics are strongest at low flows and in small events. During wettest periods, limited storage and extensive saturation weaken such controls. This study demonstrated that montane catchments can have highly dynamic GW stores, which are important in generating both storm flows and baseflows. Copyright © 2016 John Wiley & Sons, Ltd.     

Groundwater isoscapes in a montane headwater catchment show dominance of well‐mixed storage

We conducted an integrated groundwater–surface water monitoring programme in a 3.2‐km² experimental catchment in the Scottish Highlands by sampling all springs, seepages, and wells in six, spatially extensive synoptic surveys over a 2‐year period. The catchment has been glaciated, with steep hillslopes and a flat valley bottom. There is around 70% glacial drift cover in lower areas. The solid geology, which outcrops at higher elevations, is granite and metamorphic schist. The springs and seepages generally occur at the contact between the solid geology and drift or at breaks of slopes in the valley bottom. Samples were analysed for stable isotopes, Gran alkalinity and electrical conductivity. Despite the surveys encompassing markedly different antecedent conditions, the isotopic composition of groundwater at each location exhibited limited temporal variability, resulting in a remarkable persistence of spatial patterns indicating well‐mixed shallow, groundwater stores. Moreover, line‐conditioned excess values derived from the isotope data indicated no evidence of fractionation affecting the groundwater, which suggests that most recharge occurs in winter. The alkalinity and electrical conductivity of groundwater reflected geological differences in the catchment, being highest where more weatherable calcareous rocks outcrop at higher altitudes in the catchment. Springs draining these areas also had the most variable isotope composition, which indicated that they have shorter residence times than the drift covered part of the catchment. The study showed that even in geologically heterogeneous upland catchments, groundwater can be characterized by a consistent isotopic composition, reflecting rapid mixing in the recharge zone. Our work, thus, emphasizes the critical role of groundwater in upland catchments and provides tracer data that can help constrain quantitative groundwater models.