Coupling parameters of the MIT OBS at two nearshore sites

A model representing the coupling of an ocean-bottom seismometer (OBS) to the seafloor as a mass-spring-dashpot system satisfactorily explains the results of transient tests performed on different instruments during the Lopez Island intercomparison test. In this paper, we compare the results obtained for the MIT OBS at Lopez Island to results from similar tests at a dockside site at Woods Hole, Massachusetts. The vertical instrument response at the Lopez Island site shows a highly damped resonance at a frequency of 22 Hz, whereas the response at the Woods Hole site shows a marked resonance at 13 Hz. The difference between the responses at the two sites can be qualitatively attributed to the difference between the surficial sediments.     

Volcanic stratigraphy of DSDP/ODP Hole 395A: An interpretation using well-logging data

Deep Sea Drilling Project/Ocean Drilling Program Hole 395A was drilled approximately 500 m deep into young oceanic crust west of the Mid-Atlantic Ridge. Core recovery is very poor in this hole and therefore continuous downhole measurements are important to understand the drilled lithology. Geophysical downhole measurements were carried out during several cruises. A new set of logs was recorded during Leg 174B in summer 1997. The new logging data show a significant improvement in data quality compared to older measurements from Leg 109. The lithostratigraphy established from cores gives only limited information because of the poor core recovery in this hole. The gaps in the core lithostratigraphy are filled by reconstructing a synthetic lithological profile using the standard well-logging data. Three types of lava morphologies, massive basalts, altered lava flows, and pillow basalts, may be distinguished using the logs because the lava morphologies show differences in their physical properties due to differences in fracturing and alteration. The synthetic lithological profile gives a more detailed and precise vertical definition of single layers than the core profile. The integration of further logging and core data enables a detailed reconstruction of the accretion history at the drill site. Cyclic, upward decreasing trends in the resistivity logs were already observed during earlier cruises and were referred to magmatic cycles. Similar trends occur in the density log and, inversely, in the total gamma ray log. The trends reflect gradual changes in fracturing, porosity, permeability, and alteration and cover depth intervals of several tens of meters. Boundaries between cycles are interpreted to correspond to periods of volcanic quiescence. Two types of boundaries may be identified. Boundaries correlating with reversals in the magnetic field and/or changes in the geochemical composition of the basalts are interpreted as long pauses. Basalts separated by these boundaries were probably fed by separate magma reservoirs. Boundaries identified only by changes in alteration but not in geochemistry are interpreted to represent shorter pauses. They separate basalts that were probably fed by the same magma chamber. This revised version was published online in November 2006 with corrections to the Cover Date.     

Ozone production potential following convective redistribution of biomass burning emissions

The effects of deep convection on the potential for forming ozone (ozone production potential) in the free troposphere have been simulated for regions where the trace gas composition is influenced by biomass burning. Cloud dynamical and photochemical simulations based on observations in 1980 and 1985 Brazilian campaigns form the basis of a sensitivity study of the ozone production potential under differing conditions. The photochemical fate of pollutants actually entrained in a cumulus event of August 1985 during NASA/GTE/ABLE 2A (Case 1) is compared to photochemical ozone production that could have occurred if the same storm had been located closer to regions of savanna burning (Case 2) and forest burning (Case 3). In each case studied, the ozone production potential is calculated for a 24-hour period following convective redistribution of ozone precursors and compared to ozone production in the absence of convection. In all cases there is considerably more ozone formed in the middle and upper troposphere when convection has redistributed NO_x, hydrocarbons and CO compared to the case of no convection.In the August 1985 ABLE 2A event, entrainment of a layer polluted with biomass burning into a convective squall line changes the free tropospheric cloud outflow column (5–13 km) ozone production potential from net destruction to net production. If it is assumed that the same cloud dynamics occur directly over regions of savanna burning, ozone production rates in the middle and upper troposphere are much greater. Diurnally averaged ozone production following convection may reach 7 ppbv/day averaged over the layer from 5–13 km-compared to typical free tropospheric concentrations of 25–30 ppbv O₃ during nonpolluted conditions in ABLE 2A. Convection over a forested region where isoprene as well as hydrocarbons from combustion can be transported into the free troposphere leads to yet higher amounts of ozone production.     

The evolution and orientation of early cycle 22 active regions

The evolution of six major active regions which appeared during the first phase of the present solar cycle (cycle 22) has been studied. It was found that the northern hemisphere regions exhibited a broad range of evolutionary behavior in which the commonly accepted normal pattern (whereby the follower flux moves preferentially polewards ahead of the leader flux) is represented only at one end of the range. At the other end of the range, the leader flux is displaced polewards of the follower flux. In the latter cases equatorward extensions of the polar coronal hole are noted.While it is emphasized that some of the regions in this study follow the more conventional pattern and that all regions in this study emerged during the early phase of cycle 22, the implications for theories of the solar polar field reversals are noted.     

Unpacking multilevel adaptation to climate change in the Great Barrier Reef,Australia

Multilevel governance is regarded as a promising approach to deal with the multidimensional nature of climate change adaptation. However, the policy context in which it is implemented is very often complex and fragmented, characterised by interacting climate and non-climate strategies. An understanding of multilevel decision-making and governance is particularly important, if desired adaptation outcomes are to be achieved. This paper examines how climate change adaptation takes place in a complex multilevel system of governance, in the context of Australia's Great Barrier Reef (GBR) region. It examines over one hundred adaptation strategies at federal, state, regional and local levels in terms of type, manifestation, purposefulness, drivers and triggers, and geographic and temporal scope. Interactions between strategies are investigated both at the same level of governance and across governance levels. This study demonstrates that multilevel approach is a necessary, but not a sufficient condition in responding to complex multiscale and multisector issues, such as climate change adaptation. Short-term adaptation measures; a predominant incremental, sectoral, top-down approach to adaptation; and the lack of a framework for managing interactions are major threats to effective climate adaptation in the GBR region. Coping with such threats will require long-term transformative action, establishing enabling conditions to support local adaptation, and, most important, creating and maintaining strategic interactions among adaptation strategies. Coordinating and integrating climate and non-climate strategies across jurisdictions and policy sectors are the most significant and challenging tasks for multilevel governance in the GBR region and elsewhere.     

Stellar populations in barred spirals

OASIS observations obtained at the Canada–France–Hawaii Telescope for the spiral galaxies NGC 4900 and NGC 5430 produce one spectrum for each 0.41″ element of the 11″ × 15″ field of view. This allows for the spatial characterisation of the different stellar populations. From these observations we study the young (10 Myr) and older stellar populations using evolutionary synthesis codes. Based on the gas emission lines, we find that the young populations are located in relatively small regions and dominate the integrated flux. In NGC 4900, the young populations are distributed in a bar-like structure featuring a hole near the position of the galaxy’s centre. The young stellar populations of NGC 5430 form a nuclear ring and two patches at the base of the spiral arms. Based on Mg₂ and FeI absorption lines, we find that in both galaxies, the young stars are superimposed on a relatively homogenous population of a few Gyr.     

Fusing pollen-stratigraphic and dendroclimatic proxy data to reconstruct summer temperature variability during the past 7.5?ka in subarctic Fennoscandia

A new palaeoclimatic reconstruction of mid-summer (July) temperatures for the last 7.5?ka in northern Fennoscandia is presented. It is based on two botanical proxies: spectra of fossil pollen and tree rings of Scots pine logs recovered from lacustrine sediments in the Arctic tree-line region. A newly developed method of proxy fusion is used to integrate the proxy-specific reconstructions of past summer temperature variability based on the pollen-stratigraphic and dendroclimatic data. The rationale behind the method is that the two proxies are likely to be connected to climate variability in a timescale-dependent fashion and, accordingly, the new reconstruction makes use of the low- and high-frequencies from pollen-stratigraphic and tree-ring data, respectively. The most prominent features of the new reconstruction are: (1) the long-term decline of temperatures by 2.0?°C over the past 7.5?ka, (2) the mid-Holocene warmth culminating between 5 and 4?ka as a deviation from the cooling trend, (3) the Little Ice Age cool phase between 0.7 and 0.1?ka, and (4) the subsequent warming during the past century. These periods are superimposed on year-to-year variations in climate as dated to calendar-year accuracy by dendrochronology. Within the modern period, the years 1934 and 1937 are among the warmest, and the years 1903 and 1910 are among the coldest summers in the context of the past 7.5?ka. On average, the reconstructed Holocene climate was approximately 0.85?°C warmer than the twentieth century.     

Using helicopter electromagnetic data to predict groundwater quality in fractured crystalline bedrock in a semi-arid region, Northeast Brazil

Geostatistical modeling, using airborne and borehole electromagnetic data, was used to estimate electrical conductivity in groundwater within fractured paragneisses and migmatites in a semi-arid climate in northeastern Brazil. Despite the geologic heterogeneity of crystalline aquifers, the use of high resolution helicopter electromagnetic (HEM) data enabled the characterization of groundwater electrical conductivity where data from drilled wells were insufficient. The tacit assumption is that HEM measurements can be used to relate rock electrical conductivity to groundwater electrical conductivity. In this study, the HEM data were used as an external drift variable in non-stationary estimation and stochastic simulation to identify the variability of groundwater electrical conductivity. Validation tests, comparing predicted values for groundwater conductivity with measurements in new wells, confirmed the success of these models in locating fresh groundwater sources in crystalline bedrock.     

TSDS: high-performance merge, subset, and filter software for time series-like data

Time Series Data Server (TSDS) is a software package for implementing a server that provides fast super-setting, sub-setting, filtering, and uniform gridding of time series-like data. TSDS was developed to respond quickly to requests for long time spans of data. Data may be served from a fast database, typically created by aggregating granules (e.g., data files) from a remote data source and storing them in a local cache that is optimized for serving time series. The system was designed specifically for time series data, and is optimized for requests where the longest dimension of the requested data structure is time. Scalar, vector, and spectrogram time series types are supported. The user can interact with the server by requesting a time series, a date range, and an optional filter to apply to the data. Available filters include strides, block average/minimum/maximum, exclude, and inequality. Constraint expressions are supported, which allow such operations as a request for data from one time series when a different time series satisfied a specified relationship. TSDS builds upon DAP (Data Access Protocol), NcML (netCDF Mark-up language) and related software libraries. In this work, we describe the current design of this server, as well as planned features and potential implementation strategies.