Future projections of synoptic weather types over the Arabian Peninsula during the twenty-first century using an ensemble of CMIP5 models

An assessment of future change in synoptic conditions over the Arabian Peninsula throughout the twenty-first century was performed using 20 climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) database. We employed the mean sea level pressure (SLP) data from model output together with NCEP/NCAR reanalysis data and compared the relevant circulation types produced by the Lamb classification scheme for the base period 1975–2000. Overall, model results illustrated good agreement with the reanalysis, albeit with a tendency to underestimate cyclonic (C) and southeasterly (SE) patterns and to overestimate anticyclones and directional flows. We also investigated future projections for each circulation-type during the rainy season (December–May) using three Representative Concentration Pathways (RCPs), comprising RCP2.6, RCP4.5, and RCP8.5. Overall, two scenarios (RCP4.5 and RCP 8.5) revealed a statistically significant increase in weather types favoring above normal rainfall in the region (e.g., C and E-types). In contrast, weather types associated with lower amounts of rainfall (e.g., anticyclones) are projected to decrease in winter but increase in spring. For all scenarios, there was consistent agreement on the sign of change (i.e., positive/negative) for the most frequent patterns (e.g., C, SE, E and A-types), whereas the sign was uncertain for less recurrent types (e.g., N, NW, SE, and W). The projected changes in weather type frequencies in the region can be viewed not only as indicators of change in rainfall response but may also be used to inform impact studies pertinent to water resource planning and management, extreme weather analysis, and agricultural production.     

Effects of climatic change and climatic variability on the Thornthwaite moisture index in the Delaware River basin

The Thornthwaite moisture index is useful as an indicator of the supply of water in an area relative to the demand under prevailing climatic conditions. This study examines the effects of long-term changes in climate (temperature and precipitation) on the Thornthwaite moisture index in the Delaware River basin. Temperature and precipitation estimates for doubled-CO₂ conditions derived from three general circulation models (GCMs) are used to study the response of the moisture index for steady-state doubled-CO₂ conditions and for gradual changes from present to doubled-CO₂ conditions.Results of the study indicate that temperature and precipitation under doubled-CO₂ conditions will cause the Thornthwaite moisture index to decrease, implying significantly drier conditions in the Delaware River basin than currently exist. The amount of decrease depends, however, on the GCM climatic-change scenario used. The results also indicate that future changes in the moisture index will be partly masked by natural year-to-year variability in temperature and precipitation.     

The He i 10 830 Å chromosphere and filament associated structures

Full disk, He I 10 830 Å solar spectroheliograms have been generated using the Haleakala Stokes polarimeter-spectrometer. The spectroheliograms, with spatial resolution of 10 × 16 arc sec and wavelength bandpass of 0.53 Å, were developed for the detection of coronal holes, and have been compared with nearly simultaneous H and Ca K flltergrams.Areas of reduced helium absorption have been noted in the neighborhood of filaments and neutral zones in the longitudinal solar magnetic field. The existence of these helium lanes is discussed in terms of their relationship to H filament channels or to the coronal cavities which surround prominences.     

Uranium-series and AMS C studies of modern phosphatic pellets from Peru shelf muds

Recent sediments and separated phosphate pellets ( 125–500 μm in diameter) from the Peru shelf have been analyzed for uranium decay-series isotopes and ¹⁴C in order to determine age relationships and mineralization rates. Uranium-series ages of pellets separated from one box core are significantly higher than AMS radiocarbon ages determined for the same pellets. These differences appear to be a consequence of mixing of an older generation of pellets with ones which are more recently formed. Postdepositional adsorption of reactive elements such as thorium and protactinium onto pellet surfaces may also contribute to the observed discordancy with radiocarbon ages.

Sediment radiocarbon and ²¹⁰Pb sediment results, as well as some trends in the uranium-series data, suggest that high concentrations of phosphate pellets have accumulated in some Peru shelf sediments without extensive reworking. Individual pellets apparently form very quickly, on time scales of a few years. Estimated authigenic uptake rates of phosphorus into pellets ranges from 0.5 to 9.40 μmol-P cm^{− 2} yr^{− 1}, somewhat higher than rates measured for nodules from the same area. This is consistent with observations that pelletal morphologies predominate over nodular forms within ancient phosphorite deposits.     

Evidence for Heinrich event 1 in the British Isles

In the north Irish Sea basin (ISB), sedimentary successions constrained by AMS ¹⁴C dates obtained from marine microfaunas record three major palaeoenvironmental shifts during the last deglacial cycle. (i) Marine muds (Cooley Point Interstadial) dated to between 16.7 and 14.7 ¹⁴C kyr BP record a major deglaciation of the ISB following the Late Glacial Maximum (LGM). (ii) Terminal outwash and ice-contact landforms (Killard Point Stadial) were deposited during an extensive ice readvance, which occurred after 14.7 ¹⁴C kyr BP and reached a maximum extent at ca.14 ¹⁴C kyr BP. At this time the lowlands surrounding the north ISB were drumlinised. Coeval flowlines reconstructed from these bedforms end at prominent moraines (Killard Point, Bride, St Bees) and indicate contemporaneity of drumlinisation from separate ice dispersal centres, substrate erosion by fast ice flow, and subglacial sediment transfer to ice-sheet margins. In north central Ireland bed reorganisation associated with this fast ice-flow phase involved overprinting and drumlinisation of earlier transverse ridges (Rogen-type moraines) by headward erosion along ice streams that exited through tidewater ice margins. This is the first direct terrestrial evidence that the British Ice Sheet (BIS) participated in Heinrich event 1 (H1). (iii) Regional mud drapes, directly overlying drumlins, record high relative sea-level (RSL) with stagnation zone retreat after 13.7 ¹⁴C kyr BP (Rough Island Interstadial). Elsewhere in lowland areas of northern Britain ice-marginal sediments and morainic belts record millennial-scale oscillations of the BIS, which post-date the LGM advance on to the continental shelf, and pre-date the Loch Lomond Stadial (Younger Dryas) advance in the highlands of western Scotland (ca. 11–10 ¹⁴C kyr BP). In western, northwestern and northern Ireland, Killard Point Stadial (H1) ice limits are reconstructed from ice-flow lines that are coeval with those in the north ISB and end at prominent moraines. On the Scottish continental shelf possible H1-age ice limits are reconstructed from dated marine muds and associated ice marginal moraines. It is argued that the last major offshore ice expansion from the Scottish mountains post-dated ca. 15 ¹⁴C kyr BP and is therefore part of the H1 event. In eastern England the stratigraphic significance of the Dimlington silts is re-evaluated because evidence shows that there was only one major ice oscillation post-dating ca.18 ¹⁴C kyr BP in these lowlands. In a wider context the sequence of deglacial events in the ISB (widespread deglaciation of southern part of the BIS → major readvance during H1 → ice sheet collapse) is similar to records of ice sheet variability from the southern margins of the Laurentide Ice Sheet (LIS). Well-dated ice-marginal records, however, show that during the Killard Point readvance the BIS was at its maximum position when retreat of the LIS was well underway. This phasing relationship supports the idea that the BIS readvance was a response to North Atlantic cooling induced by collapse of the LIS. © 1998 John Wiley & Sons, Ltd.     

Pb-isotopic compositions of volcanic rocks in the West and East Philippine island arcs: presence of the Dupal isotopic anomaly

The Philippine islands are situated between two oppositely dipping zones of seismicity. With the exception of a few areas, such as in the west central Philippines where the North Palawan continental terrane (NPCT) has collided with the archipelago, these seismic zones are well defined to depths of 200 km. Active volcanic chains overlay segments in each of these zones, suggesting that subduction is presently taking place both east and west of the islands. Lavas we have studied are thus divided between what has been termed the West Philippine arc and the East Philippine arc.West Philippine arc volcanic rocks which were extruded before the Philippine archipelago collided with the NPCT, or which are younger than the collision but crop out hundreds of kilometers from the collision zone, and all but one of the rocks from the East Philippine arc fall in the MORB field on²⁰⁷Pb/²⁰⁴Pb versus²⁰⁶Pb/²⁰⁴Pb covariation diagrams. This is surprising considering the frequency with which arc materials have²⁰⁷Pb/²⁰⁴Pb ratios higher than those of MORB, the highBa/REE and Sr/REE ratios in the lavas and the possibility of sediment subduction given the small accretionary prisms. All of these rocks have high²⁰⁸Pb/²⁰⁴Pb ratios with respect to Pacific and Atlantic Ocean MORB, but are similar to Indian Ocean MORB and IOB. Thus the Philippines consist of island arcs with the peculiar Dupal isotopic anomaly documented between 0° and 60°S in the southern hemisphere and particularly in the Indian Ocean region. This demonstrates that the Dupal isotopic anomaly is not restricted to the southern hemisphere, or to MORB and OIB.Post-collision rocks cropping out near the NPCT, in the West Philippine arc, have elevated²⁰⁸Pb/²⁰⁴Pb and ²⁰⁷Pb/²⁰⁴Pb ratios that could be attributed to assimilation of the newly introduced continental crust (NPCT) by mantle-derived magmas or to the addition of a sedimentary component to mantle-derived magmas.     

A commentary on climate change, stone decay dynamics and the ‘greening’ of natural stone buildings: new perspectives on ‘deep wetting’

Environmental controls on stone decay processes are rapidly changing as a result of changing climate. UKCP09 projections for the 2020s (2010–2039) indicate that over much of the UK seasonality of precipitation will increase. Summer dryness and winter wetness are both set to increase, the latter linked to projected precipitation increases in autumn and spring months. If so, this could increase the time that stone structures remain wet and possibly the depth of moisture penetration, and it appears that building stone in Northern Ireland has already responded through an increased incidence of algal ‘greening’. This paper highlights the need for understanding the effects of climate change through a series of studies of largely sandstone structures. Current and projected climatic trends are therefore considered to have aesthetic, physical and chemical implications that are not currently built into our models of sandstone decay, especially with respect to the role played by deep-seated wetness on sandstone deterioration and decay progression and the feedbacks associated with, for example surface algal growth. In particular, it is proposed that algal biofilms will aid moisture retention and further facilitate moisture and dissolved salt penetration to depth. Thus, whilst the outer surface of stone may continue to experience frequent wetting and drying associated with individual precipitation events, the latter is less likely to be complete, and the interiors of building blocks may only experience wetting/drying in response to seasonal cycling. A possible consequence of deeper salt penetration could be a delay in the onset of surface deterioration, but more rapid and effective retreat once it commences as decay mechanisms ‘tap into a reservoir of deep salt’.     

STEREOMICROSCOPE PHOTOGRAMMETRY FOR THE MEASUREMENT OF SMALL OBJECTS

A stereoscopic microscope has been used in combination with the body of a 35 mm camera to obtain stereophotographs, at scales up to 6:1, of objects only a few millimetres in size. Subsequent stereocomparator observations have been used to deduce height differences on the objects 10 a precision, for the mean of five sets of readings, of ±0.01 mm for closely spaced points. Using more widely separated points, the precision was estimated to be ± 0.05 mm. Depths were computed using × parallaxes after a number of parameters were fixed by calibration. The large convergence angle of the microscope axes was a crucial parameter; rotations about the camera axis were found to be significant variables.     

Paleomagnetism of the Upper Silurian and Lower Devonian carbonates of New York State: evidence for secondary magnetizations residing in magnetite

Paleomagnetic directions for the Upper Silurian and Lower Devonian carbonates of the Helderberg escarpment (New York State) differ from expected Late Silurian and Early Devonian directions for cratonic North America. The mean direction (D = 165°, I = −10°; paleopole at 50°N 129°E) is similar to Late Carboniferous and Early Permian results. Negative fold tests, and a lack of reversals, suggest that the magnetization is secondary. However, low coercivities, low blocking temperatures, the thermomagnetic curves (T_C near 570°C) and the acquisition of isothermal remanent magnetizations all suggest that the remanence is carried by magnetite. If a detrital origin of these magnetites is assumed, the secondary nature of the remanence would argue for thermal resetting as a result of deep burial of the rocks. However, no evidence for such thermal resetting is seen in the alteration of conodonts. More likely perhaps is a chemical or thermochemical origin of the remanence; this would require the magnetites to be authigenic.