The Kwakshua Watersheds Observatory,central coast of British Columbia,Canada

The Kwakshua Watersheds Observatory (KWO) is an integrative watersheds observatory on the coastal margin of a rain-dominated bog-forest landscape in British Columbia (BC), Canada. Established in 2013, the goal of the KWO is to understand and model the flux of terrestrial materials from land to sea – the origins, pathways, processes and ecosystem consequences – in the context of long-term environmental change. The KWO consists of seven gauged watersheds and a network of observation sites spanning from land to sea and along drainage gradients within catchments. Time-series datasets include year-round measurements of weather, soil hydrology, streamflow, aquatic biogeochemistry, microbial ecology and nearshore oceanographic conditions. Sensor measurements are recorded every 5 min and water samples are collected approximately monthly. Additional observations are made during high-flow conditions. We used remote sensing to map watershed terrain, drainage networks, soils and terrestrial ecosystems. The watersheds range in size from 3.2 to 12.8 km², with varying catchment characteristics that influence hydrological and biogeochemical responses. Despite local variation, the overall study area is a global hotspot for yields of dissolved organic carbon, dissolved organic nitrogen and dissolved iron at the coastal margin. This observatory helps fill an important gap in the global network of observatories, in terms of spatial location (central coast of BC), climate (temperate oceanic), hydrology (very high runoff, pluvial regime), geology (igneous intrusive, glacially scoured), vegetation (bog rainforest) and soils (large stores of organic carbon).     

Assessing characteristics of Mediterranean explosive cyclones for different data resolution

A comparison of two objective climatologies of explosive cyclones in the Mediterranean region is performed. The results are derived from two different mean sea-level pressure reanalysis data resolutions, but from the same assimilation model, in order to quantify the pure impact of higher resolution on the identification and characteristics of explosive cyclones, when the assimilation model is the same. The explosive cyclones were identified with the aid of the Melbourne University automatic cyclone finding and tracking scheme over a 40-year period, using the 6-hourly analyses of ERA-40 mean sea-level pressure (MSLP) on: (a) 2.5?×?2.5 and (b) 1?×?1 latitude–longitude grid. The comparison of the two datasets revealed the significant role of the increase in spatial resolution of MSLP data on the identification and tracking process, and the number of the explosive cyclones in the high-resolution dataset is almost four times greater than the respective one in the lower resolution dataset. However, the comparison of explosive cyclone characteristics, including spatial and temporal variations of explosive deepening, revealed differences in the geographical distribution of the location of the maximum explosive deepening and average explosive cyclone Laplacian of the central pressure. These differences are due to the identification in the higher resolution set of smaller scale and secondary explosives along the strongly baroclinic northern Mediterranean boundaries, south of the Alps and the Pyrenees. Explosive deepening appears a bias to the daytime period from 12 to 18 Coordinated Universal Time (UTC) for both datasets, which is more prominent in the LR dataset. Statistically significant difference of pressure tendency between the two datasets appear for the daytime period from 06 to 12 UTC, accounting for better representation of orographic forcing in the HR dataset.     

Pacific Atmospheric Sulfur Experiment (PASE): dynamics and chemistry of the south Pacific tropical trade wind regime

The Pacific Atmospheric Sulfur Experiment (PASE) was a comprehensive airborne study of the chemistry and dynamics of the tropical trade wind regime (TWR) east of the island of Kiritibati (Christmas Island, 157º, 20?? W, 2º 52?? N). Christmas Island is located due south of Hawaii. Geographically it is in the northern hemisphere yet it is 6?C12º south of the intertropical convergence zone (ITCZ) which places it in the southern hemisphere meteorologically. Christmas Island trade winds in August and September are from east south east at 3?C15 ms^?1. Clouds, if present, are fair weather cumulus located in the middle layer of the TWR which is frequently labeled the buffer layer (BuL). PASE provided clear support for the idea that small particles (80 nm) were subsiding into the tropical trade wind regime (TWR) where sulfur chemistry transformed them to larger particles. Sulfur chemistry promoted the growth of some of these particles until they were large enough to activate to cloud drops. This process, promoted by sulfur chemistry, can produce a cooling effect due to the increase in cloud droplet density and changes in cloud droplet size. These increases in particle size observed in PASE promote additional cooling due to direct scattering from the aerosol. These potential impacts on the radiation balance in the TWR are enhanced by the high solar irradiance and ocean albedo of the TWR. Finally because of the large area involved there is a large factional impact on earth??s radiation budget. The TWR region near Christmas Island appears to be similar to the TWR that persists in August and September, from southwest of the Galapagos to at least Christmas Island. Transport in the TWR between the Galapagos and Christmas involves very little precipitation which could have removed the aerosol thus explaining at least in part the high concentrations of CCN (??300 at 0.5% supersaturation) observed in PASE. As expected the chemistry of sulfur in the trade winds was found to be initiated by the emission of DMS into the convective boundary layer (BL, the lowest of three layers). However, the efficiency with which this DMS is converted to SO₂ has been brought into further question by this study. This unusual result has come about as result of our using two totally different approaches for addressing this long standing question. In the first approach, based on accepted kinetic rate constants and detailed steps for the oxidation of DMS reflecting detailed laboratory studies, a DMS to SO₂ conversion efficiency of 60?C73% was determined. This range of values lies well within the uncertainties of previous studies. However, using a completely different approach, involving a budget analysis, a conversion value of 100% was estimated. The latter value, to be consistent with all other sulfur studies, requires the existence of a completely independent sulfur source which would emit into the atmosphere at a source strength approximately half that measured for DMS under tropical Pacific conditions. At this time, however, there is no credible scientific observation that identifies what this source might be. Thus, the current study has opened for future scientific investigation the major question: is there yet another major tropical marine source of sulfur? Of equal importance, then, is the related question, is our global sulfur budget significantly in error due to the existence of an unknown marine source of sulfur? Pivotal to both questions may be gaining greater insight about the intermediate DMS oxidation species, DMSO, for which rather unusual measurements have been reported in previous marine sulfur studies. The 3 pptv bromine deficit observed in PASE must be lost over the lifetime of the aerosol which is a few days. This observation suggests that the primary BrO production rate is very small. However, considering the uncertainties in these observations and the possible importance of secondary production of bromine radicals through aerosol surface reactions, to completely rule out the importance of bromine chemistry under tropical conditions at this time cannot be justified. This point has been brought into focus from prior work that even at levels of 1 pptv, the effect of BrO oxidation on DMS can still be quite significant. Thus, as in the case of DMS conversion to SO₂, future studies will be needed. In the latter case there will need to be a specific focus on halogen chemistry. Such studies clearly must involve specific measurements of radical species such as BrO.     

Calibration of GA1550 biotite standard for K/Ar and 40Ar/39Ar dating

The mineral separate GA1550 biotite has become an international standard for K/Ar and ⁴⁰Ar/³⁹Ar dating studies, although it was prepared as an intralaboratory standard at ANU to monitor tracer depletion from a gas pipette. It is one of a small number of samples that has been calibrated against ³⁸Ar tracers, some of which had been mixed with known amounts of atmospheric argon, so that a so-called primary calibration has been performed. By measuring GA1550 biotite against additional tracers from the same batch we have determined the radiogenic argon content of this sample as 1.342 (± 0.007) × 10^? 9 mol/g, and together with the measured K content of 7.645 (± 0.050) weight percent, we derive a best estimate for the K/Ar age as 98.5 ± 0.5 Ma, where the error is derived from averaging the ages determined relative to the ³⁸Ar tracer.     

The Lower Albian (Lower Cretaceous) Monk's Bay Sandstone Formation (formerly the Carstone) of the Isle of Wight: Its distribution, litho- and biostratigraphy

The Monk's Bay Sandstone Formation (MBSF) is the new name for the Lower Albian ferruginous sandstone that was formerly known as the Carstone of the Isle of Wight. The new term was proposed to remove any confusion with the Carstone, of similar age and lithology, described from the separate Lower Cretaceous sedimentary basin of Eastern England. This paper formalises the nomenclatural change outlined in the Lower Cretaceous Framework Report, ratified by the Geological Society Stratigraphy Commission.The MBSF, representing a major mid-Albian transgressive event, is described from a series of boreholes drilled by the British Geological Survey across the Isle of Wight, and from additional coastal exposures, together with reinterpretations of sections described in earlier works.The age range of the MBSF is determined in relation to recent biostratigraphical schemes supported with new data from the previously unknown presence of foraminifera. Deposits, belonging to the Leymeriella regularis Subzone, were previously considered to be absent from the succession and represent the stratigraphical gap separating the formation from the underlying Sandrock Formation. However a first occurrence of tubular foraminifera resembling Hyperammina/‘Rhizammina cf dichotomata’ suggest that the oldest part of the formation in the northeast of the island may be of regularis Subzone age. This unconformity is correlated with the sequence boundary LG4 of Hesselbo and the presence of the Sonneratia kitchini Subzone at the base of the MBSF on the Isle of Wight suggests that this boundary should be placed at the lower of two candidate horizons within the successions of the Weald.The formation is restricted to the Isle of Wight but is coeval with similar coarse-grained sediments, e.g. the Carstone and ‘JunctionBeds’ to the north. The palaeogeography of the formation and the relationship with these similar deposits and the implications for the timing of mid-Albian structural events is briefly discussed. The identification of older Lower Greensand Group sediments beneath the MBSF in boreholes north of the Isle of Wight structure, together with new survey data indicating north-south orientated faulting affecting the early Cretaceous implies a tectonic element to the distribution the Lower Greensand Group sediments. Taken together these imply a complex interaction of tectonics and transgressive events throughout the Aptian and Albian over this structural high.     

The stratigraphical distribution of mid-Cretaceous Foraminifera near Ventnor, Isle of Wight

Ventnor No. 2 Borehole, located near Ventnor, Isle of Wight, penetrated the basal part of the Chalk Group and the Selborne Group before terminating in the upper part of the Lower Greensand Group (Sandrock Formation). The borehole was examined for Foraminifera, and although they were not seen in the Sandrock Formation and Monks Bay Sandstone Formation, the remainder of the borehole yielded moderately low diversity assemblages dominated by agglutinated species. Foraminiferal zones 3-6 (H dentatus to M. fallax/M. rostratum macrofaunal zones) were identified in the Gault Formation and zones 6 (lower) to 6a (M. fallax/M. rostratum to A. briacensis macrofaunal zones) were identified in the Upper Greensand Formation. Assemblages from the overlying West Melbury Marly Chalk Formation were used to identify foraminiferal zones BGS1-BGS3 (M. mantelli and M. dixoni macrofaunal zones).     

Size, speciation and lability of NOM-metal complexes in hyperalkaline cave dripwater

Transport of trace metals by natural organic matter (NOM) is potentially an important vector for trace metal incorporation in secondary cave precipitates [speleothems], yet little is known about the size distribution, speciation and metal binding properties of NOM in cave dripwaters. A hyperalkaline cave environment (ca. pH 11) was selected to provide information on colloid-metal interactions in cave waters, and to address the lack of high-pH data in natural systems in general. Colloidal (1 nm-1 μm) NOM in hyperalkaline cave dripwater from Poole’s Cavern, UK, was characterised by flow field-flow fractionation (FlFFF) coupled to UV and fluorescence detectors and transmission electron microscopy (TEM) coupled to X-ray energy-dispersive spectroscopy (X-EDS); trace-metal lability was examined by diffusive gradients in thin films (DGT). Colloidal aggregates and small particulates (>1 μm) imaged by TEM were morphologically heterogeneous with qualitative elemental compositions (X-EDS spectra; n = 41) consistent with NOM aggregates containing aluminosilicates, and iron and titanium oxides. Globular organic colloids, with diameters between ca. 1 and 10 nm were the most numerous colloidal class and exhibited high UV-absorbance (254 nm) and fluorescence intensity (320:400 nm excitation: emission) in optical regions characteristic of humic-like compounds. Metal binding with humic substances was modelled using the WHAM 6.1 (model VI) and visual MINTEQ 3.0 (NICA-Donnan) speciation codes. At pH 11, both models predicted dominant humic binding of Cu (ca. 100%) and minimal binding of Ni and Co (ca. <1-7%). A DGT depletion experiment (7 days duration) with the hyperalkaline dripwater showed that the available proportion of each metal was much lower than its total concentration. Metal availability for DGT in the initial stages (24 h) was consistent with weaker binding of alkaline earth metals by humic substances (Ba > Sr > V > Cu > Ni > Co), compared to the transition metals. Integrated over the entire experiment, the DGT-available proportion of transition metals (Ni > Cu & V >> Co) differed greatly from the expected hierarchy from WHAM and MINTEQ, indicating unusually strong complexation of Co. Total metal concentrations of Cu, Ni, and Co in raw and filtered PE1 dripwater samples (n = 53) were well correlated (Cu vs. Ni, R² = 0.8; Cu vs. Co, R² = 0.5) and were strongly reduced (> ca. 50%) by filtration at ca. 100 and 1 nm, indicating a common colloidal association. Our results demonstrate that soil-derived colloids reach speleothems, despite transport through a karst zone with potential for adsorption, and that NOM is a dominant complexant of trace metals in high pH speleothem-forming groundwaters.     

Observations of fluid‐dependent shear‐wave splitting in synthetic porous rocks with aligned penny‐shaped fractures‡

P‐ and S‐wave velocity and attenuation coefficients (accurate to ±0.3% and ±0.2 dB/cm, respectively) were measured in synthetic porous rocks with aligned, penny‐shaped fractures using the laboratory ultrasonic pulse‐echo method. Shear‐wave splitting was observed by rotating the S‐wave transducer and noting the maximum and minimum velocities relative to the fracture direction. A block of synthetic porous rock of fracture density 0.0201 ± 0.0068 and fracture size 3.6 ± 0.38 mm (measured from image analysis of X‐ray CT scans) was sub‐sampled into three 20–30 mm long, 50 mm diameter core plugs oriented at 0°, 45° and 90° to the fracture normal (transversely isotropic symmetry axis). Full waveform data were collected over the frequency range 500–1000 kHz for both water and glycerin saturated cores to observe the effect of pore fluid viscosity at 1 cP and 100 cP, respectively. The shear‐wave splitting observed in the 90° core was 2.15 ± 0.02% for water saturated and 2.39 ± 0.02% for glycerin saturated, in agreement with the theory that suggests that the percentage splitting should be 100 times the fracture density and independent of the saturating fluid. In the 45° core, by contrast, splitting was 0.00 ± 0.02% for water saturation and ?0.77 ± 0.02% for glycerin saturation. This dependence on fracture orientation and pore fluid viscosity is consistent with the poro‐visco‐elastic theory for aligned, meso‐scale fractures in porous rocks. The results suggest the possible use of shear‐ or converted‐wave data to discriminate between fluids on the basis of viscosity variations.