A Portable Matched-Field Processing System Using Passive Acoustic Time Synchronization

A portable matched-field processing (MFP) system for tracking marine mammals is presented, constructed by attaching a set of autonomous flash-memory acoustic recorders to a rope to form a four-element vertical array, or "insta-array." The acoustic data are initially time-synchronized by performing a matched-field global inversion using acoustic data from an opportunistic source, and then by exploiting the spatial coherence of the ocean ambient noise background to measure and correct for the relative clock drift between the autonomous recorders. The technique is illustrated by using humpback whale song collected off the eastern Australian coast to synchronize the array, which is then used to track the dive profile of the whale using MFP methods. The ability to deploy autonomous instruments into arbitrary "insta-array" geometries with conventional fishing gear may permit nonintrusive array measurements in regions currently too isolated, expensive, or environmentally hostile for standard acoustic equipment     

The Infrared Spectral Energy Distribution of Normal Star-Forming Galaxies

We have developed a new phenomenological model for the spectral energy distribution of normal star-forming galaxies between 3 and 1100 μm. These model spectra allow us to determine the infrared energy budget for normal galaxies, and in particular to translate far-infrared fluxes into total (bolometric) infrared fluxes. The 20 to 42 m range appears to show the most significant growth in relative terms as the activity level increases, suggesting that the 20–42 m continuum may be the best dust emission tracer of current star formation in galaxies.     

Geothermobarometry, P–T paths and metamorphic field gradients of high-pressure rocks from the Adula Nappe, Central Alps

Metabasic rocks from the Adula Nappe in the Central Alps record a regional high‐pressure metamorphic event during the Eocene, and display a regional variation in high‐pressure mineral assemblages from barroisite, or glaucophane, bearing garnet amphibolites in the north to kyanite eclogites in the central part of the nappe. High‐pressure rocks from all parts of the nappe show the same metamorphic evolution of assemblages consistent with prograde blueschist, high‐pressure amphibolite or eclogite facies conditions followed by peak‐pressure eclogite facies conditions and decompression to the greenschist or amphibolite facies. Average PT calculations (using thermocalc ) quantitatively establish nested, clockwise P–T paths for different parts of the Adula Nappe that are displaced to higher pressure and temperature from north to south. Metamorphic conditions at peak pressure increase from about 17 kbar, 640 °C in the north to 22 kbar, 750 °C in the centre and 25 kbar, 750 °C in the south. The northern and central Adula Nappe behaved as a coherent tectonic unit at peak pressures and during decompression, and thermobarometric results are interpreted in terms of a metamorphic field gradient of 9.6 ± 2.0 °C km^?1 and 0.20 ± 0.05 kbar km^?1. These results constrain the peak‐pressure position and orientation of the nappe to a depth of 55–75 km, dipping at an angle of approximately 45° towards the south. Results from the southern Adula Nappe are not consistent with the metamorphic field gradient determined for the northern and central parts, which suggests that the southern Adula Nappe may have been separated from central and northern parts at peak pressure.     

Surface composition and radius of hyperion

New spectrophotometric data for Hyperion in the region 1.5–2.6 um obtained in 1981 confirm the presence of water ice bands reported by D.P. Cruikshank (1980, Icarus 41, 246–258). The bands are now shown with sufficient clarity to permit improved comparisons with other ice-bearing satellites of Jupiter and Saturn and with laboratory samples. Comparisons with Ganymede and Rhea are shown, and Hyperion is found to differ from both satellites in terms of depth and width of the water ice bands. The sense of the difference is the same as noted earlier from broadband infrared photometry, but the physical cause is not fully understood. The effective radius of Hyperion (considered circular in cross section) derived from a 20-um flux measurement and a revised value of V(1,0) = 4.62 is r = 140 ± 19 km. This result is in better accord with both preliminary and refined values of the radius derived from Voyager images; the Voyager result supercedes that deduced from infrared observations.     

TWO STATISTICS FOR THE ANALYSIS OF ORIENTATION DATA IN GEOGRAPHY*

Two versions of the A_n statistic of Ajne and Stephens are introduced, explained, interpreted and evaluated. These statistics possess important advantages over those currently used by geographers for the analysis of orientation data. They are invariant with respect to the point of origin of measurements, do not assume a circular-normal distribution and are not limited by sample size. Used in conjunction, they allow the significance of direction as well as orientation to be determined.     

A parameter study of the mixed instability of idealized ocean currents

We investigate the nature of linear instabilities that can arise on eastward-flowing baroclinic currents similar to those found to serve as sites of strong eddy-mean flow interaction in certain mesoscale-resolution ocean circulation studies. The intent is to deduce the dependence of the linear instability mechanism — thought to be operative in some form in these simulations — on the internal parameters characterizing them. Following conventional practice, we adopt as our physical model the two-level quasigeostrophic potential vorticity equations which, in their linearized form, are solved numerically to yield the properties of the most unstable linear waves under a variety of mean flow and environmental conditions. The kinematic and dynamic features of the growing perturbations — preferred wavelength, growth rate and frequency, eddy-mean field energy transfers and vertical distribution of wave amplitude — are shown to be sensitive functions of our nondimensional parameters: $\text{(}\text{i}\text{) α = (}\text{U}{}_3\text{U}{}_1\text{)}$, the ratio of lower to upper level velocity scale amplitude; $\text{(}\text{ii}\text{) X = (}\text{R}{}_{\mathrm{<mtext>d</mtext>}}\text{L}\text{)}$, the ratio of the first baroclinic deformation radius to the meridional width of the jet; $\text{(}\text{iii}\text{) δ = (}\text{H}{}_1\text{H}{}_3\text{)}$, the resting layer depth ratio; and $\text{(}\text{iv}\text{) ? = (}\text{βL}{}^2\text{U}\text{)}$, an (inverse) Rossby number based on the northward gradient of the planetary vorticity (β). Viscous effects, although included in the analysis, are shown to be unimportant for values of frictional coefficients typical of recent eddy-resolving ocean model studies. Despite a strong dependence of the details of the linear instability mechanism on environmental factors, the associated unstable eigenmodes do have important structural similarities which are intimately connected with their ability to extract energy from the mean flow.     

The Uranian satellites: Surface compositions and opposition brightness surges

High-precision spectrophotometry at 5% resolution has been obtained for the Uranian satellites Ariel, Umbriel, Titania, and Oberon. These spectra cover the wavelength region 1.43–2.57 μm and represent a substantial improvement in precision or wavelength coverage over previous studies. The presence of a spectrally dominant water-ice component in the surface of Ariel, Umbriel, Titania, and Oberon is confirmed. The 1.5- and 2.0-μm water absorption band depths and the continuum reflectance (as defined by the reflectance at 1.78 and 2.25 μm) indicate significant differences among the surface compositional properties of the four satellites. Comparisons of the new spectra to those of other solar system bodies, and to laboratory spectra of water ice of various degrees of purity, indicate that these satellites have a significant non-water-ice component on/in their surfaces. The lack of spectral absorptions at 5% resolution attributable to anything other than water ice suggests that the non-water-ice component is a roughly neutral reflector in the 1.5- to 2.5- μm region. The nature of the non-water-ice component cannot be uniquely determined from these data, but it is relatively dark and has spectral similarities to substances such as carbon black, the dark substance covering one face of Iapetus, or other neutral-color, low-reflectance materials. Finally, preliminary measurements of the near-infrared opposition brightness surges of Ariel, Titania, and Oberon show them to be among the largest in the solar system.     

Introduction to “Historical and Recent Catastrophic Tsunamis in the World: Volume II. Tsunamis from 1755 to 2010”

Eighteen papers on past and recent destructive tsunamis are included in Volume II of the PAGEOPH topical issue “Historical and Recent Catastrophic Tsunamis in the World.” Three papers discuss deep-sea (DART) and coastal tsunami observations, warning systems and risk management in the Pacific Ocean. Four papers examine the 1755 Lisbon, 1964 Alaska, 2003 Algeria, and 2011 Haiti tsunamis. Four more papers, as well as some papers in Volume I, report on various aspects of the 2010 Chile tsunami. Two papers present some results of field survey and modelling investigation of the 2010 Mentawai, Indonesia, tsunami. Three papers report on modelling efforts of tsunami generation by earthquake and landslide, and of tsunami propagation. Finally, two papers discuss hazard assessment using a probabilistic approach.