ALBERT

Beschreibung: Clouds play an important role in the Arctic surface radiative budget, impacting the seasonal evolution of Arctic sea-ice cover. We explore the large-scale impacts of springtime and early summer (March through July) cloud and radiative fluxes on sea ice by comparing these fluxes to seasonal ice volume losses over the central Arctic basin, calculated for available observational years 2004–2007 (ICESat) and 2011–2017 (CryoSat-2). We also supplement observation data with sea-ice volume computed from the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS) during summer months. We find that the volume of sea ice lost over the melt season is most closely related to observed downwelling longwave radiation in March and early summer (June and July) longwave cloud radiative forcing, which together explain a large fraction of interannual variability in seasonal sea-ice volume loss (R2 = 0.71, p = 0.007). We show that downwelling longwave fluxes likely impact the timing of melt onset near the sea-ice edge, and can limit the magnitude of ice thickening from March to April. Radiative fluxes in June and July are likely critical to seasonal volume loss because modeled data show the greatest ice volume reductions occur during these months.

Beschreibung: Two satellite datasets are used to characterize winter landfast first-year sea-ice (FYI), deformed FYI (DFYI) and multiyear sea-ice (MYI) roughness in the Canadian Arctic Archipelago (CAA): (1) optical Multi-angle Imaging SpectroRadiometer (MISR) and (2) synthetic aperture radar Sentinel-1. The Normalized Difference Angular Index (NDAI) roughness proxy derived from MISR, and backscatter from Sentinel-1 are intercompared. NDAI and backscatter are also compared to surface roughness derived from an airborne LiDAR track covering a subset of FYI and MYI (no DFYI). Overall, NDAI and backscatter are significantly positively correlated when all ice type samples are considered. When individual ice types are evaluated, NDAI and backscatter are only significantly correlated for DFYI. Both NDAI and backscatter are correlated with LiDAR-derived roughness (r = 0.71 and r = 0.74, respectively). The relationship between NDAI and roughness is greater for MYI than FYI, whereas for backscatter and ice roughness, the relationship is greater for FYI than MYI. Linear regression models are created for the estimation of FYI and MYI roughness from NDAI, and FYI roughness from backscatter. Results suggest that using a combination of Sentinel-1 backscatter for FYI and MISR NDAI for MYI may be optimal for mapping winter sea-ice roughness in the CAA.

Beschreibung: A Fast Ice Prediction System (FIPS) was constructed and is the first regional land-fast sea-ice forecasting system for the Antarctic. FIPS had two components: (1) near-real-time information on the ice-covered area from MODIS and SAR imagery that revealed, tidal cracks, ridged and rafted ice regions; (2) a high-resolution 1-D thermodynamic snow and ice model (HIGHTSI) that was extended to perform a 2-D simulation on snow and ice evolution using atmospheric forcing from ECMWF: either using ERA-Interim reanalysis (in hindcast mode) or HERS operational 10-day predictions (in forecast mode). A hindcast experiment for the 2015 season was in good agreement with field observations, with a mean bias of 0.14 ± 0.07 m and a correlation coefficient of 0.98 for modeled ice thickness. The errors are largely caused by a cold bias in the atmospheric forcing. The thick snow cover during the 2015 season led to modeled formation of extensive snow ice and superimposed ice. The first FIPS operational service was performed during the 2017/18 season. The system predicted a realistic ice thickness and onset of snow surface melt as well as the area of internal ice melt. The model results on the snow and ice properties were considered by the captain of R/V Xuelong when optimizing a low-risk route for on-ice transportation through fast ice to the coastal Zhongshan Station.

Beschreibung: The evolution of melt ponds on Arctic sea ice in summer is one of the main factors that affect sea-ice albedo and hence the polar climate system. Due to the different spectral properties of open water, melt pond and sea ice, the melt pond fraction (MPF) can be retrieved using a fully constrained least-squares algorithm, which shows a high accuracy with root mean square error ~0.06 based on the validation experiment using WorldView-2 image. In this study, the evolution of ponds on first-year and multiyear ice in the Canadian Arctic Archipelago was compared based on Sentinel-2 and Landsat 8 images. The relationships of pond coverage with air temperature and albedo were analysed. The results show that the pond coverage on first-year ice changed dramatically with seasonal maximum of 54%, whereas that on multiyear ice changed relatively flat with only 30% during the entire melting period. During the stage of pond formation, the ponds expanded rapidly when the temperature increased to over 0°C for three consecutive days. Sea-ice albedo shows a significantly negative correlation (R = −1) with the MPF in melt season and increases gradually with the refreezing of ponds and sea ice.

Beschreibung: Quantifying the rate of wave attenuation in sea ice is key to understanding trends in the Antarctic marginal ice zone extent. However, a paucity of observations of waves in sea ice limits progress on this front. We deployed 14 waves-in-ice observation systems (WIIOS) on Antarctic sea ice during the Polynyas, Ice Production, and seasonal Evolution in the Ross Sea expedition (PIPERS) in 2017. The WIIOS provide in situ measurement of surface wave characteristics. Two experiments were conducted, one while the ship was inbound and one outbound. The sea ice throughout the experiments generally consisted of pancake and young ice

Beschreibung: Research Articles Lan Duong, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 444-462 Abstract

Beschreibung: Research Articles John Ingleson, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 205-226 Abstract

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉We argue in this article that the social and economic conditions in the Angkorian society of the tenth century or earlier contributed to the decline in status of some middle-level officials, as is evident from the mid-eleventh century. Many Angkorian inscriptions written between the late ninth and late twelfth centuries record purchases and donations of lands acquired for religious foundations. The texts often contain details of transactions and disputes seeking to validate title to these holdings. The buyers include middle-ranking 〈span〉loñ〈/span〉 and 〈span〉vāp〈/span〉, and increasingly, higher-ranking officials. An analysis of the roles and activities of the officials reveals something of their relative status and helps explain the disappearance of 〈span〉vāp〈/span〉 from the inscriptions in the eleventh century, and the relegation of 〈span〉loñ〈/span〉 to temple roles by the twelfth century. The transfer of communal lands and lands owned by these officials to elites is attributed to hierarchical restrictions on land purchases, a reduction in fiscal immunities, and the need for taxes to be paid to the centre with high-value goods in Angkor's moneyless economy.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Lord Reid played a vital role as chairman in a Commonwealth commission in framing the Malayan Independence constitution between 1956 and 1957. The Scottish Lord of Appeal sought to ensure the commission's impartiality and to achieve a fair balance between the demands of the various interest groups. The Federation of Malaya was a complex emerging nation-state with a diverse population and the framers had to manage competing interests and demands. This article, through a close examination of the primary constitutional documents, considers Reid's influence on the framing of the Malayan (and hence, Malaysian) federal constitution. The article begins with a brief discussion of Lord Reid's appointment to head the commission and then considers in some depth areas where his influence on the framing of the draft constitution is evident. The article argues that Reid was the main playmaker and moderator during the constitution-framing process and played a critical role in ensuring a balance was achieved between the competing demands of the federal government and the states, safeguarding the fundamental rights of the citizens against the state, and in moderating the various communal demands.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Successive wars and the establishment of a border between the kingdom of Burma and British India in the nineteenth century challenged Burmese conceptions of sovereignty and political space. This essay investigates how European, and more specifically Anglo-American, notions of race, nation, and consular protection to nationals, progressively informed the Burmese concepts of ‘categories of people’ 〈span〉(lumyo)〈/span〉 and ‘subject’ 〈span〉(kyun)〈/span〉. First, I present the semantic evolution of these concepts in the 1820s–1830s, following the annexation of the western Burmese province of Arakan by British India in 1824. Then, I argue that the Burmese concept of 〈span〉lumyo〈/span〉 was progressively associated with the European concept of ‘nations’ in the 1850s–1860s, following the annexation of Lower Burma in 1852. Finally, I uncover developments in the 1870s, when British consular protection extended to several freshly categorised ‘nations’, such as Shan, Karenni, and Kachin.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉This volume contains an introduction and eight papers presented at an international symposium ‘Let's Talk about Trees’, which was organised by Ritsuko Kikusawa and hosted by the National Museum of Ethnology of Osaka, Japan, in February 2013. The stated purpose of the meeting was to evaluate the pros and cons of the classic tree model of historical linguistics in describing the order of splits within a language family. Because the problem of modelling relationships of descent is common to other disciplines, contributors were invited from a range of academic disciplines, including not only linguistics, but also what is described on page one as ‘cladistics’, ‘biology’ and ‘genetics’, although cladistics is clearly a part of biological taxonomy, and not an independent discipline.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉We recorded the ice motion and icequakes on the floating part of Langhovde Glacier in East Antarctica to better understand the dynamic behavior of ice shelves and floating tongues. Diurnal and semi-diurnal variations in ice motion and seismicity were simultaneously observed at all four global navigation satellite system and three seismic stations over 2 weeks. The short-term along-flow ice motion is explained by the elastic response of the glacier to ocean tide-induced hydrostatic stress variations, which decayed at a rate of 0.8 km〈span〉−1〈/span〉 toward the grounding line. We observed a large number of icequakes during mid-rising and high tides that covered a broad frequency range and formed two major groups of events centered at 10 and 120 Hz, respectively. The hourly occurrence rates were ~500 events h〈span〉−1〈/span〉, with the observed seismicity consistent with fracture due to floating tongue bending. We also observed minor secondary peaks at high ice speeds, which could reflect surface cracking due to stretching or basal friction. Our observation demonstrates that tidal-modulation was the main factor to fracture the floating tongue of Langhovde Glacier.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Changing rates of water input can affect both the flow of glaciers and ice sheets and their propensity to crevasse. Here we examine geodetic and seismic observations during two substantial (10–18-times background velocity) rain-induced glacier accelerations at Haupapa/Tasman Glacier, New Zealand. Changes in rain rate result in glacier acceleration and associated uplift, which propagate down-glacier. This pattern of acceleration results in a change to the strain rate field, which correlates with an order of magnitude increase in the apparent seismicity rate and an overall down-glacier migration in located seismicity. After each acceleration event the apparent seismicity rate decreases to below the pre-acceleration rate for 3 days. This suggests that seismic events associated with surface crevasse growth occur early during phases of glacier acceleration due to elevated extensional stresses, and then do not occur again until stresses recover.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉We compared elastic moduli in polar firn derived from diving wave refraction seismic velocity analysis, firn-core density measurements and microstructure modelling based on firn-core data. The seismic data were obtained with a small electrodynamic vibrator source near Kohnen Station, East Antarctica. The analysis of diving waves resulted in velocity–depth profiles for different wave types (P-, SH- and SV-waves). Dynamic elastic moduli of firn were derived by combining P- and S-wave velocities and densities obtained from firn-core measurements. The structural finite-element method (FEM) was used to calculate the components of the elastic tensor from firn microstructure derived from X-ray tomography of firn-core samples at depths of 10, 42, 71 and 99 m, providing static elastic moduli. Shear and bulk moduli range from 0.39 to 2.42 GPa and 0.68 to 2.42 GPa, respectively. The elastic moduli from seismic observations and the structural FEM agree within 8.5% for the deepest achieved values at a depth of 71 m, and are within the uncertainty range. Our observations demonstrate that the elastic moduli of the firn can be consistently obtained from two independent methods which are based on dynamic (seismic) and static (tomography and FEM) observations, respectively, for deeper layers in the firn below ~10 m depth.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉This article provides an outline of the historical construction of Timorese (East Timorese and Indonesian West Timorese) geo-bodies and communal identities from the mid-nineteenth century to the present time, thereby reconstructing the origins of many national imaginings amongst the Timorese people. Since the controversial annexation of Portuguese Timor by Indonesia in 1976, (East) Timor has been constructed as a place of two territorial identities: Timor as a part of Indonesia and East Timor as a homogeneous nation distinct from Indonesia. However, representations of Timor had been much more fluid and inconsistent in preceding ages. This article studies various communities’ representations of Timor to reveal dialectic relations between diverse colonial and post-colonial representations of the Timorese spaces and their senses of belonging. Thereby, it problematises the political role of global and regional place-making in a contested Southeast Asian locale.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉This article examines 〈span〉gotong royong〈/span〉 as social citizenship in the second half of the twentieth century in Indonesia. 〈span〉Gotong royong〈/span〉 was traditionally understood as a collective spirit among neighbours to strengthen economic and social resilience. However, the institutionalisation of the system through massive development programmes since the 1940s has influenced the common people's perception and practice of it. This article argues that the co-option of 〈span〉gotong royong〈/span〉 as part of the discourse of nation-state building transformed the popular view of labour and capital mobilisation from an openly critical stance to apparent submission. 〈span〉Gotong royong〈/span〉 became a means of social engineering and an ingenious linguistic strategy by which state elites orchestrated control over the making of citizens. Still, Indonesians have remained vigilant of their participation in 〈span〉gotong royong〈/span〉, and about the potential for its misuse by corrupt officials.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉The evolution of glaciers and ice sheets depends on processes in the subglacial environment. Shear seismicity along the ice–bed interface provides a window into these processes. Such seismicity requires a rapid loss of strength that is typically ascribed to rate-weakening friction, i.e., decreasing friction with sliding or sliding rate. Many friction experiments have investigated glacial materials at the temperate conditions typical of fast flowing glacier beds. To our knowledge, however, these studies have all found rate-strengthening friction. Here, we investigate the possibility that rate-weakening rock-on-rock friction between sediments frozen to the bottom of the glacier and the underlying water-saturated sediments or bedrock may be responsible for subglacial shear seismicity along temperate glacier beds. We test this ‘entrainment-seismicity hypothesis’ using targeted laboratory experiments and simple models of glacier sliding, seismicity and sediment entrainment. These models suggest that sediment entrainment may be a necessary but not sufficient condition for the occurrence of basal shear seismicity. We propose that stagnation at the Whillans Ice Stream, West Antarctica may be caused by the growth of a frozen fringe of entrained sediment in the ice stream margins. Our results suggest that basal shear seismicity may indicate geomorphic activity.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Geophysicists that deploy seismic sensors in ablation zones of glaciers and ice sheets to record glaciogenic signatures can confront recording challenges caused by instrument melt-out or tilt. These challenges often require installing sensors in boreholes to delay melt-out, or securing sensors to structures that improve coupling. We show that some of these structures that were buried near a moulin at a snow-free site in the ablation zone of the Western Greenland Ice Sheet resonated as they became exposed, and caused their geophones to record temporally evolving, narrowband signals that mimic features of glaciogenic sources like moulin tremor. We quantify these artifacts with a mechanical model that shows instruments undergo structural resonance as they melt-out, at exposure rates that we predict from an ablation model (RACMO). These models reproduce general spectral features in our data, and enable us to estimate what instrument exposure reduces ice-to-sensor coupling enough to prevent icequake detection. Last, we use our resonance data to quantitatively measure how narrowband signals that originate from either artificial or glaciogenic sources will reduce the ability of certain waveform detectors (correlators) to capture transient seismic events, even if sensors remain coupled.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉GPS measurements of tidal modulation of ice flow and seismicity within the grounding zone of Beardmore Glacier show that tidally induced fluctuations of horizontal flow are largest near the grounding line and decrease downstream. Seismic activity is continuous, but peaks occur on falling and rising tides. Beamforming methods reveal that most seismic events originate from two distinct locations, one on the grid-north side of the grounding zone, and one on the grid-south side. The broad pattern of deformation generated as Beardmore Glacier merges with the Ross Ice Shelf results in net extension along the grid-north side of the grounding zone and net compression along the grid-south side. During falling tides, seismic activity peaks on both sides because of increased vertical flexure across the grounding line. During rising tides, seismic activity in the region of extension on the grid-north side is relatively low because the tidal influence on both horizontal strain rate and vertical flexure is small. On the grid-south side during rising tides, however, tidally induced horizontal strain rates promote increased seismicity in regions of long-term compressional flow paths. Our study highlights how concurrent geodetic and seismic measurements provide insight into grounding-zone mechanics and their influence on ice-shelf buttressing.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Englacial hydrology plays an important role in routing surface water to the glacier's bed and it consequently affects the glacier's dynamics. However, it is often difficult to observe englacial conduit conditions on temperate glaciers because of their short-lived nature. We acquired repeated active surface seismic data over the Rhone Glacier, Switzerland to monitor and characterise englacial conduit conditions. Amplitude-versus-angle analysis suggested that the englacial conduit is water filled and between 0.5 and 4 m thick. A grid of GPR profiles, acquired during the 2018 melt season, showed the englacial conduit network persisting and covering ~ 14,000 m〈span〉2〈/span〉. In late summer 2018, several boreholes were drilled into the conduit network. We observed generally stable water pressure, but there were also short sudden increases. A borehole camera provided images of a fast flowing englacial stream transporting sediment through the conduit. From these observations, we infer that the englacial conduit network is fed by surface meltwater and morainal streams. The surface and morainal streams merge together, enter the glacier subglacially and flow through subglacial channels along the flank. These subglacial channels flow into highly efficient englacial conduits traversing the up-glacier section of the overdeepening before connecting with the subglacial drainage system.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Icequakes at or near the bed of a glacier have the potential to allow us to investigate the interaction of ice with the underlying till or bedrock. Understanding this interaction is important for studying basal sliding of glaciers and ice streams, a critical process in ice dynamics models used to constrain future sea-level rise projections. However, seismic observations on glaciers can be dominated by seismic energy from surface crevassing. We present a method of automatically detecting basal icequakes and discriminating them from surface crevassing, comparing this method to a commonly used spectrum-based method of detecting icequakes. We use data from Skeidararjökull, an outlet glacier of the Vatnajökull Ice Cap, South-East Iceland, to demonstrate that our method outperforms the commonly used spectrum-based method. Our method detects a higher number of basal icequakes, has a lower rate of incorrectly identifying crevassing as basal icequakes and detects an additional, spatially independent basal icequake cluster. We also show independently that the icequakes do not originate from near the glacier surface. We conclude that the method described here is more effective than currently implemented methods for detecting and discriminating basal icequakes from surface crevassing.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Hydraulic processes within and beneath glacial bodies exert a far-reaching control on ice flow through their influence on basal sliding. Within the subglacial system, rapid changes in these processes may excite resonances whose interpretation requires an understanding of the underlying wave mechanics. Here, we explore these mechanics using observations from a kHz-sampled pressure sensor installed in a borehole directly above the hard granite bedrock of a temperate mountain glacier in Switzerland. We apply a previously established theory of wave propagation along thin, water-filled structures such as water-filled voids, basal water layers, or hydraulic fractures. Within such structures, short-wavelength waves experience restoring forces due to compressibility and are composed of sound waves. Long-wavelength resonances, in contrast, experience restoring forces due to elasticity and are composed of anomalously dispersed crack waves or Krauklis waves. Our borehole observations confirm the occurrence of both sound and crack waves within the basal water layer. Using both the resonance frequencies and attenuation of recorded crack waves we estimate thickness, aperture and length of the resonating basal water layer patch into which we drilled. We demonstrate that high-frequency observations of subglacial hydraulic processes provide new insights into this evolving dynamic system.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Forced ice-shelf vibration modeling is performed using a full 3-D finite-difference elastic model, which also takes into account sub-ice seawater flow. The sea water flow is described by the wave equation. Ice-shelf flexure therefore results from hydrostatic pressure perturbations in the sub-ice seawater layer. Numerical experiments were undertaken for idealized rectangular ice-shelf geometry. The ice-plate vibrations were modeled for harmonic incoming pressure perturbations and for a wide range of incoming wave frequencies. The spectra showed distinct resonant peaks, which demonstrate the ability of the model to simulate a resonant-like motion. The spectra obtained by the full 3-D model are compared with exact solutions for the elastic thin plate with two fixed edges and two free edges. The spectra are also compared with the spectra modeled by the thin-plate Holdsworth and Glynn model (1978).〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉We conducted a 9-d seismic experiment in October 2015 at Laohugou Glacier No. 12. We identified microseismic signals using the short-term/long-term average trigger algorithm at four stations and classified them as long and short-duration events based on waveform, frequency, duration and magnitude characteristics. Both categories show systematical diurnal trends. The long-duration events are low-frequency tremor-like events that mainly occurred during the daytime with only several events per day. These events lasted tens of seconds to tens of minutes and are likely related to resonance of daytime meltwater. The dominant short-duration events mostly occurred during the night time with a peak occurrence frequency of ~360 h〈span〉−1〈/span〉. Their short-duration (〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Passive seismology allows measurement of the structure of glaciers and ice sheets. However, most techniques used so far in this context are based on horizontally homogeneous media where parameters vary only with depth (1-D approximations), which are appropriate only for a subset of glaciers. Here, we analyze seismic noise records from three different types of glaciers (plateau, valley and avalanching glacier) to characterize the influence of the glacier geometry on the seismic wavefield. Using horizontal-to-vertical spectral ratios, polarization analysis and modal analysis, we show that the plateau glacier and the valley glacier can be seen as 1-D, whereas the relatively small avalanching glacier shows 3-D effects due to its bed topography and the deep crevasses. In principle, the techniques proposed here might allow monitoring such crevasses and their depth, and thus to constrain a key parameter of avalanching and calving glacier fronts.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Crevasses and englacial fracture networks route meltwater from a glacier's surface to the subglacial drainage system and thus influence glacial hydraulics. However, rapid fracture growth may also lead to sudden and potentially hazardous structural failure of unstable glaciers and ice dams, rifting of ice shelves, or iceberg calving. Here, we use passive seismic recordings to investigate the englacial fracture network on Glacier de la Plaine Morte, Switzerland. Glacier dynamics and the drainage of an ice-marginal lake give rise to numerous icequakes, the majority of which generate dispersed, high-frequency Rayleigh waves. A wide distribution of events allows us to study azimuthal anisotropy between 10 and 30 Hz in order to extract englacial seismic velocities in regions of preferentially oriented crevasses. Beamforming applied to a 100-m-aperture array reveals azimuthal anisotropy of Rayleigh-wave phase velocities reaching a strength of 8% at high frequencies. In addition, we find that the fast direction of wave propagation coincides with the observed surface strike of the narrow crevasses. Forward modeling and inversion of dispersion curves suggest that the azimuthal anisotropy is induced by a 40-m-thick crevassed layer at the surface of the glacier with 8% anisotropy in shear-wave velocity.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Seismograms acquired on the McMurdo Ice Shelf, Antarctica, during an Austral summer melt season (November 2016–January 2017) reveal a diurnal cycle of seismicity, consisting of hundreds of thousands of small ice quakes limited to a 6–12 hour period during the evening, in an area where there is substantial subsurface melting. This cycle is explained by thermally induced bending and fracture of a frozen surface superimposed on a subsurface slush/water layer that is supported by solar radiation penetration and absorption. A simple, one-dimensional model of heat transfer driven by observed surface air temperature and shortwave absorption reproduces the presence and absence (as daily weather dictated) of the observed diurnal seismicity cycle. Seismic event statistics comparing event occurrence with amplitude suggest that the events are generated in a fractured medium featuring relatively low stresses, as is consistent with a frozen surface superimposed on subsurface slush. Waveforms of the icequakes are consistent with hydroacoustic phases at frequency 〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20190807170601246-0716:S0260305518000290:S0260305518000290_inline1.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉 and flexural-gravity waves at frequency 〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20190807170601246-0716:S0260305518000290:S0260305518000290_inline2.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉. Our results suggest that seismic observation may prove useful in monitoring subsurface melting in a manner that complements other ground-based methods as well as remote sensing.〈/p〉〈/div〉

Beschreibung: Research Articles Robert Dayley, Attachak Sattayanurak, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 42-65 Abstract

Beschreibung: Book Reviews Donna Brunero, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 144-145 Abstract

Beschreibung: Research Articles Anthony Reid, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 88-108 Abstract

Beschreibung: Book Reviews Gareth Curless, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 153-156 Abstract

Beschreibung: Book Reviews Edgar Liao, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 156-157 Abstract

Beschreibung: Book Reviews Carool Kersten, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 322-324 Abstract

Beschreibung: Book Reviews Eve Monique Zucker, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 339-341 Abstract

Beschreibung: Book Reviews Jonathan Rigg, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 336-337 Abstract

Beschreibung: Book Reviews Gerard Sasges, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 337-339 Abstract

Beschreibung: Book Reviews Brian P. Farrell, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 320-322 Abstract

Beschreibung: Book Reviews Catherine Ceniza Choy, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 330-332 Abstract

Beschreibung: Article Commentary James Ockey, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 293-309 Abstract

Beschreibung: Research Articles Nile Green, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 175-204 Abstract

Beschreibung: Book Reviews Nordin Hussin, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 314-316 Abstract

Beschreibung: Book Reviews Ruth de Llobet, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 332-334 Abstract

Beschreibung: Book Reviews Nicolai Volland, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 326-328 Abstract

Beschreibung: Book Reviews Alicia Turner, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 328-330 Abstract

Beschreibung: Book Reviews Erik W. Davis, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 318-320 Abstract

Beschreibung: Research Articles Tam T.T. Ngo, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 274-292 Abstract

Beschreibung: Editorial Maurizio Peleggi, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 173-174 Abstract

Beschreibung: Research Articles Upik Djalins, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 227-245 Abstract

Beschreibung: Book Reviews Murari Jha, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 310-312 Abstract

Beschreibung: Book Reviews Astrid Norén-Nilsson, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 312-314 Abstract

Beschreibung: Book Reviews Garth Pratten, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 316-318 Abstract

Beschreibung: Research Articles Shin’ya Ueda, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 246-273 Abstract

Beschreibung: Book Reviews Boike Rehbein, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 324-326 Abstract

Beschreibung: Book Reviews Robert L. Brown, Journal of Southeast Asian Studies , Volume 46 Issue 02 , pp 334-336 Abstract

Beschreibung: Editorial Maurizio Peleggi, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 343-345 Abstract

Beschreibung: Research Articles Rebecca S. Hall, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 346-367 Abstract

Beschreibung: Research Articles Nathan Porath, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 368-390 Abstract

Beschreibung: Research Articles Sharyn Graham Davies, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 417-443 Abstract

Beschreibung: Research Articles Yvonne Low, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 463-484 Abstract

Beschreibung: Article Commentary Denise Tsui, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 537-545 Abstract

Beschreibung: Research Articles Josh Stenberg, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 391-416 Abstract

Beschreibung: Research Articles Jim Sykes, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 485-513 Abstract

Beschreibung: Research Articles Swati Chemburkar, Journal of Southeast Asian Studies , Volume 46 Issue 03 , pp 514-536 Abstract

Beschreibung: Editorial Maurizio Peleggi, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 1-2 Abstract

Beschreibung: Research Articles Alexandra Kent, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 3-23 Abstract

Beschreibung: Research Articles Lisa Arensen, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 24-41 Abstract

Beschreibung: Research Articles Brendan Luyt, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 66-87 Abstract

Beschreibung: Book Reviews Kania A. Sukotjo, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 148-149 Abstract

Beschreibung: Obituaries Albert Lau, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 141-143 Abstract

Beschreibung: Research Articles Olivier Évrard, Thomas O. Pryce, Guido Sprenger, Chanthaphilith Chiemsisouraj, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 109-140 Abstract

Beschreibung: Book Reviews Rommel A. Curaming, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 145-147 Abstract

Beschreibung: Book Reviews Hiroko Kawanami, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 151-153 Abstract

Beschreibung: Book Reviews Frank Fanselow, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 149-151 Abstract

Beschreibung: Book Reviews Andrea Katalin Molnar, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 161-163 Abstract

Beschreibung: Book Reviews Tamara Loos, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 159-161 Abstract

Beschreibung: Book Reviews Eli Elinoff, Journal of Southeast Asian Studies , Volume 47 Issue 01 , pp 158-159 Abstract

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉This article explores how the islands of Bali and Lombok were racialised through the work of Dutch racial scientist J.P. Kleiweg de Zwaan in the 1930s. An examination of both Kleiweg's published works and his local practices draws attention to the fact that racialisation occurred at different moments of anthropological work, producing different outcomes. The article concludes that anthropologists communicated different versions of racial ideas to international academics and to local communities. The Bali-Aga and Sasak, who were measured, described and photographed by anthropologists, appropriated racial categories which they found meaningful.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉The United States’ occupation of the Philippines began with proclamations of a new era of development and the prospect of local political representation. In coming to grips with what they saw as America's civilising mission, colonial scholars and officials sought information about the peoples of the Philippines by conducting a census and various population studies, using an array of methodologies drawn from criminology and physical anthropology. This article traces and critiques representations of the Philippine population in the 1903 Philippine Census as well as in several related studies published in the early American period, which served to reduce the Filipinos to a state of ‘otherness’ which served to justify colonial projects. Several of these racialised studies used the inmates of Bilibid Prison, both alive and dead, as experimental and documentary subjects to create a record of Filipino ‘sample types’ for various administrative and other purposes, such as the exhibition at the St Louis World's Fair of 1904. Bilibid prisoners’ body size, brain weight, skin colour, facial features and other physical attributes were selectively correlated with other colonial constructions of Filipino individuals and groups, such as ‘wildness’ and political maturity.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉In the 1920s and 1930s, the Mestizos of Kisar, a dry, almost barren island in the Dutch East Indies off the coast of East Timor, were a model for the study of race mixing or human hybridity. Discovered in the late nineteenth century, these ‘anomalous blondes’ of Dutch and Kisarese ancestry became subjects of intense scrutiny by physical anthropologists. As a German specialist in tropical medicine in search of a convenient empire after 1918, Ernst Rodenwaldt favourably evaluated the physique and mentality of the isolated, fair Mestizos in the Dutch East Indies (now Indonesia). Back in Germany in the 1930s, as professor of hygiene at Heidelberg, his views on race hardened to accord with Nazi doctrine. Yet after the war, Rodenwaldt successfully cited his earlier appreciation of mixed-race peoples in the eastern Malay Archipelago as grounds for rehabilitation. Once a celebrated case study in human hybridity, the Mestizos of Kisar were erased from anthropological discussion in the 1950s, when race mixing ceased to be a biological issue and became instead a sociological interest. Still, Rodenwaldt's work continues to exert some limited influence in the eastern parts of the archipelago and among the Kisarese diaspora, indicating the penetrance and resilience of colonial racialisation projects.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉The response of the atmospheric boundary layer (ABL) to subgrid-scale variations of sea ice properties and fracturing is poorly understood and not taken into account in mesoscale Numerical Weather Prediction (NWP) model parametrizations. In this paper we analyze three-dimensional air circulation within the ABL over fragmented sea ice. A series of idealized high-resolution simulations with the Weather Research and Forecasting (WRF) model is performed for several spatial distributions of ice floes and leads for two values of sea ice concentration (0.5 and 0.9) and several ambient wind speed profiles. The results show that the convective circulation within the ABL is sensitive to the subgrid-scale spatial distribution of sea ice. Considerable variability of several domain-averaged quantities – cloud liquid water content, surface turbulent heat flux (THF) – is found for different arrangements of floes. Moreover, the organized structure of air circulation leads to spatial covariance of variables characterizing the ABL. Based on the example of THF, it is demonstrated that this covariance may lead to substantial errors when THF values are estimated from area-averaged quantities, as it is done in mesoscale NWP models. This suggests the need for developing suitable parametrizations of ABL effects related to subgrid-scale sea ice features for these models.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Significant salinity anomalies have been observed in the Arctic Ocean surface layer during the last decade. Our study is based on an extensive gridded dataset of winter salinity in the upper 50 m layer of the Arctic Ocean for the periods 1950–1993 and 2007–2012, obtained from ~20 000 profiles. We investigate the interannual variability of the salinity fields, identify predominant patterns of anomalous behavior and leading modes of variability, and develop a statistical model for the prediction of surface-layer salinity. The statistical model is based on linear regression equations linking the principal components of surface-layer salinity obtained through empirical orthogonal function decomposition with environmental factors, such as atmospheric circulation, river runoff, ice processes and water exchange with neighboring oceans. Using this model, we obtain prognostic fields of the surface-layer salinity for the winter period 2013–2014. The prognostic fields generated by the model show tendencies of surface-layer salinification, which were also observed in previous years. Although the used data are proprietary and have gaps, they provide the most spatiotemporally detailed observational resource for studying multidecadal variations in basin-wide Arctic salinity. Thus, there is community value in the identification, dissemination and modeling of the principal modes of variability in this salinity record.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉In this paper an algorithm for ice/water classification of C- and L-band dual polarization synthetic aperture radar data is presented. A comparison of the two different frequencies is made in order to investigate the potential to improve classification results with multi-frequency data. The algorithm is based on backscatter intensities in co- and cross-polarization and autocorrelation as a texture feature. The mapping between image features and ice/water classification is made with a neural network. Accurate ice/water maps for both frequencies are produced by the algorithm and the results of two frequencies generally agree very well. Differences are found in the marginal ice zone, where the time difference between acquisitions causes motion of the ice pack. C-band reliably reproduces the outline of the ice edge, while L-band has its strengths for thin ice/calm water areas within the icepack. The classification shows good agreement with ice/water maps derived from met.no ice-charts and radiometer data from AMSR-2. Variations are found in the marginal ice zone where the generalization of the ice charts and lower accuracy of ice concentration from radiometer data introduce deviations. Usage of high-resolution dual frequency data could be beneficial for improving ice cover information for navigation and modelling.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Sea-ice thickness in the Sea of Okhotsk is estimated for 2004–2008 from ICESat derived freeboard under the assumption of hydrostatic balance. Total ice thickness including snow depth (〈span〉h〈/span〉〈span〉〈span〉t〈/span〉〈span〉o〈/span〉〈span〉t〈/span〉〈/span〉) averaged over 2004–2008 is 95 cm. The interannual variability of 〈span〉h〈/span〉〈span〉〈span〉t〈/span〉〈span〉o〈/span〉〈span〉t〈/span〉〈/span〉 is large; from 77.5 cm (2008) to 110.4 cm (2005). The mode of 〈span〉h〈/span〉〈span〉〈span〉t〈/span〉〈span〉o〈/span〉〈span〉t〈/span〉〈/span〉 varies from 50–60 cm (2007 and 2008) to 70–80 cm (2005). Ice thickness derived from ICESat data is validated from a comparison with that observed by Electromagnetic Induction Instrument (EM) aboard the icebreaker 〈span〉Soya〈/span〉 near Hokkaido, Japan. Annual maps of 〈span〉h〈/span〉〈span〉〈span〉t〈/span〉〈span〉o〈/span〉〈span〉t〈/span〉〈/span〉 reveal that the spatial distribution of 〈span〉h〈/span〉〈span〉〈span〉t〈/span〉〈span〉o〈/span〉〈span〉t〈/span〉〈/span〉 is similar every year. Ice volume of 6.3 × 10〈span〉11〈/span〉 m〈span〉3〈/span〉 is estimated from the ICESat derived 〈span〉h〈/span〉〈span〉〈span〉t〈/span〉〈span〉o〈/span〉〈span〉t〈/span〉〈/span〉 and AMSR-E derived ice concentration. A comparison with ice area demonstrates that the ice volume cannot always be represented by the area solely, despite the fact that the area has been used as a proxy of the volume in the Sea of Okhotsk. The ice volume roughly corresponds to that of annual ice production in the major coastal polynyas estimated based on heat budget calculations. This also supports the validity of the estimation of sea-ice thickness and volume using ICESat data.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉The presence of leads with open water or thin ice is an important feature of the Arctic sea ice cover. Leads regulate the heat, gas and moisture fluxes between the ocean and atmosphere and are areas of high ice growth rates during periods of freezing conditions. Here, an algorithm providing an automatic lead detection based on synthetic aperture radar images is described that can be applied to a wide range of Sentinel-1 scenes. By using both the HH and the HV channels instead of single co-polarised observations the algorithm is able to classify more leads correctly. The lead classification algorithm is based on polarimetric features and textural features derived from the grey-level co-occurrence matrix. The Random Forest classifier is used to investigate the importance of the individual features for lead detection. The precision–recall curve representing the quality of the classification is used to define threshold for a binary lead/sea ice classification. The algorithm is able to produce a lead classification with more that 90% precision with 60% of all leads classified. The precision can be increased by the cost of the amount of leads detected. Results are evaluated based on comparisons with Sentinel-2 optical satellite data.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Pressure ridges impact the mass, energy and momentum budgets of the sea-ice cover and present an obstacle to transportation through ice-infested waters. Quantifying ridge characteristics is important for understanding total sea-ice mass and for improving the representation of sea-ice dynamics in high-resolution models. Multi-sensor measurements collected during annual Operation IceBridge (OIB) airborne surveys of the Arctic provide new opportunities to assess the sea ice at the end of winter. We present a new methodology to derive ridge sail height from high-resolution OIB Digital Mapping System (DMS) visible imagery. We assess the efficacy of the methodology by mapping the full sail height distribution along 12 pressure ridges in the western and central Arctic. Comparisons against coincident Airborne Topographic Mapper (ATM) elevation anomalies are used to demonstrate the methodology and evaluate DMS-derived sail heights. Sail heights and elevation anomalies were correlated at 0.81 or above. On average mean and maximum sail height agreed with ATM elevation to within 0.11 and 0.49 m, respectively. Of the ridges mapped, mean sail height ranged from 0.99 to 2.16 m, while maximum sail height ranged from 2.1 to 4.8 m. DMS also delivered higher sampling along ridge crests than coincident ATM data.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Large discrepancies have been observed between satellite-derived sea-ice concentrations(IC) from passive microwave remote sensing and those derived from optical images at several locations in the East Antarctic, between February and April 2014. These artefacts, that resemble polynyas in the IC maps, appear in areas where optical satellite data show that there is landfast sea ice. The IC datasets and the corresponding retrieval algorithms are investigated together with microwave brightness temperature, air temperature, snowfall and bathymetry to understand the failure of the IC retrieval. The artefacts are the result of the application of weather filters in retrieval algorithms. These filters use the 37 and 19 GHz channels to correct for atmospheric effects on the retrieval. These channels show significant departures from typical ranges when the artefacts occur. A melt–refreeze cycle with associated snow metamorphism is proposed as the most likely cause. Together, the areas of the artefacts account for up to 0.5% of the Antarctic sea-ice area and thus cause a bias in sea-IC time series. In addition, erroneous sea ICs can adversely affect shipping operations.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Knowledge of Arctic sea-ice conditions is of great interest for Arctic residents, as well as for commercial usage, and to study the effects of climate change. Information gained from analysis of satellite data contributes to this understanding. In the course of using in situ data in combination with remotely sensed data, the question of how representative local scale measurements are of a wider region may arise. We compare in situ total sea-ice thickness measurements from the Norwegian young sea ICE expedition in the area north of Svalbard with airborne-derived total sea-ice thickness from electromagnetic soundings. A segmented and classified synthetic aperture radar (SAR) quad-pol ALOS-2 Palsar-2 satellite scene was grouped into three simplified ice classes. The area fractions of the three classes are: 11.2% ‘thin’, 74.4% ‘level’, and 14.4% ‘deformed’. The area fractions of the simplified classes from ground- and helicopter-based measurements are comparable with those achieved from the SAR data. Thus, this study shows that there is potential for a stepwise upscaling from in situ, to airborne, to satellite data, which allow us to assess whether in situ data collected are representative of a wider region as observed by satellites.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Research on young thin sea ice is essential to understand the changes in the Arctic. But it is also the most challenging to investigate, both in situ and from satellites. If satellite remote-sensing techniques are developing rapidly, fieldwork remains crucial for the mandatory validation of such data. In April 2016, an Arctic fieldwork campaign was conducted at Kongsfjorden, Svalbard. This campaign provided an opportunity to combine various techniques to record the fjord ice properties ranging from local field sampling to broader ground-based and satellite radar remote sensing of the fjord. Tracking the boat used to access the field sites with hand-held GPS devices offered a good opportunity to map fjord ice and assess the limits of radar identification of small icebergs and thin ice. During 1 week, 17 icebergs and the thin ice edges in two different locations were mapped. The GPS tracks present a good agreement with the Radarsat-2 data analysis for one of the two ice edges. The second ice edge track only partly corresponds to the radar scene. Ice movement, recorded by a ground-based radar, is likely to explain this result. Grounded icebergs could be identified in both Radarsat-2 and ground-based radar.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Changing Arctic sea-ice extent and melt season duration, and increasing economic interest in the Arctic have prompted the need for enhanced marine ecosystem studies and improvements to dynamical and forecast models. Sea-ice melt pond fraction 〈span〉f〈/span〉〈span〉p〈/span〉 has been shown to be correlated with the September minimum ice extent due to its impact on ice albedo and heat uptake. Ice forecasts should benefit from knowledge of 〈span〉f〈/span〉〈span〉p〈/span〉 as melt ponds form several months in advance of ice retreat. This study goes further back by examining the potential to predict 〈span〉f〈/span〉〈span〉p〈/span〉 during winter using backscatter data from the commonly available Sentinel-1 synthetic aperture radar. An object-based image analysis links the winter and spring thermodynamic states of first-year and multiyear sea-ice types. Strong correlations between winter backscatter and spring 〈span〉f〈/span〉〈span〉p〈/span〉, detected from high-resolution visible to near infrared imagery, are observed, and models for the retrieval of 〈span〉f〈/span〉〈span〉p〈/span〉 from Sentinel-1 data are provided (〈span〉r〈/span〉〈span〉2〈/span〉 ≥ 0.72). The models utilize HH polarization channel backscatter that is routinely acquired over the Arctic from the two-satellite Sentinel-1 constellation mission, as well as other past, current and future SAR missions operating in the same C-band frequency. Predicted 〈span〉f〈/span〉〈span〉p〈/span〉 is generally representative of major ice types first-year ice and multiyear ice during the stage in seasonal melt pond evolution where 〈span〉f〈/span〉〈span〉p〈/span〉 is closely related to spatial variations in ice topography.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉The Arctic marine environment is undergoing a transition from thick multi-year to first-year sea-ice cover with coincident lengthening of the melt season. Such changes are evident in the Baffin Bay-Davis Strait-Labrador Sea (BDL) region where melt onset has occurred ~8 days decade〈span〉−1〈/span〉 earlier from 1979 to 2015. A series of anomalously early events has occurred since the mid-1990s, overlapping a period of increased upper-air ridging across Greenland and the northwestern North Atlantic. We investigate an extreme early melt event observed in spring 2013. (~6〈span〉σ〈/span〉 below the 1981–2010 melt climatology), with respect to preceding sub-seasonal mid-tropospheric circulation conditions as described by a daily Greenland Blocking Index (GBI). The 40-days prior to the 2013 BDL melt onset are characterized by a persistent, strong 500 hPa anticyclone over the region (GBI 〉+1 on 〉75% of days). This circulation pattern advected warm air from northeastern Canada and the northwestern Atlantic poleward onto the thin, first-year sea ice and caused melt ~50 days earlier than normal. The episodic increase in the ridging atmospheric pattern near western Greenland as in 2013, exemplified by large positive GBI values, is an important recent process impacting the atmospheric circulation over a North Atlantic cryosphere undergoing accelerated regional climate change.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉This article analyses the changing significance of racial theories in the writings of Spanish emigrants in the late nineteenth century Philippines. Works by Antonio Cañamaque, Pablo Feced (Quioquiap), and Antonio Barrantes show how racialised understandings of colonial society in the Philippines evolved, from an initial dismissal of hybridism and rejection of mestizos to assertions of the innate superiority of the ‘white race’ and advocation of a rigid separation between local communities. These developments are considered in the context of the rising popularity of biological determinism alongside an influx of Spanish emigrants into the Philippines. The Spanish settlers used biological determinism to proclaim their role as the sole purveyors of both ‘progress’ and of a kind of egalitarianism. This article describes these debates and arguments, analyses their inconsistencies, and addresses the Filipino elite's responses to the settlers’ racial theories. These responses are read not simply as part of the development of Filipino nationalism, but as reflective of rivalries within the Spanish colonial community in the Philippines, where the locally born found additional reasons to support anticolonialism.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉With rapid and accelerated Arctic sea-ice loss, it is beneficial to update and baseline historical change on the regional scales from a consistent, intercalibrated, long-term time series of sea-ice data for understanding regional vulnerability and monitoring ice state for climate adaptation and risk mitigation. In this paper, monthly sea-ice extents (SIEs) derived from a passive microwave sea-ice concentration climate data record for the period of 1979–2015, are used to examine Arctic-wide and regional temporal variability of sea-ice cover and their decadal trends for 15 regions of the Arctic. Three unique types of SIE annual cycles are described. Regions of vulnerability within each of three types to further warming are identified. For the Arctic as a whole, the analysis has found significant changes in both annual SIE maximum and minimum, with −2.41 ± 0.56% per decade and −13.5 ± 2.93% per decade change relative to the 1979–2015 climate average, respectively. On the regional scale, the calculated trends for the annual SIE maximum range from +2.48 to −10.8% decade〈span〉−1〈/span〉, while the trends for the annual SIE minimum range from 0 to up to −42% decade〈span〉−1〈/span〉.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉We present a highly detailed study of calving dynamics at Tunabreen, a tidewater glacier in Svalbard. A time-lapse camera was trained on the terminus and programmed to capture images every 3 seconds over a 28-hour period in August 2015, producing a highly detailed record of 34 117 images from which 358 individual calving events were distinguished. Calving activity is characterised by frequent events (12.8 events h〈span〉−1〈/span〉) that are small relative to the spectrum of calving events observed, demonstrating the prevalence of small-scale calving mechanisms. Five calving styles were observed, with a high proportion of calving events (82%) originating at, or above, the waterline. The tidal cycle plays a key role in the timing of calving events, with 68% occurring on the falling limb of the tide. Calving activity is concentrated where meltwater plumes surface at the glacier front, and a ~ 5 m undercut at the base of the glacier suggests that meltwater plumes encourage melt-under-cutting. We conclude that frontal ablation at Tunabreen may be paced by submarine melt rates, as suggested from similar observations at glaciers in Svalbard and Alaska. Using submarine melt rate to calculate frontal ablation would greatly simplify estimations of tidewater glacier losses in prognostic models.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Ice shelves regulate the rate of ice-sheet discharge along much of the Antarctic coastline. Pinning points, sites of localised grounding within floating ice, can in turn, regulate the flow and thickness of an ice shelf. While the net resistive effect of ice shelves has been quantified in a systematic way, few extant pinning points have been examined in detail. Here, complete force budgets are calculated and examined for ice rises and rumples in the Ross Ice Shelf, West Antarctica. The diverse features have different effects on ice shelf mechanics that do not depend simply on their size but may, we conclude, depend on the properties of seafloor materials.〈/p〉〈/div〉

Beschreibung: 〈div data-abstract-type="normal"〉〈p〉Measurements of a sample from ~580 m depth in the WAIS Divide (WDC06A) ice core reveal that bubbles are preferentially elongated in the basal plane of their parent grain, as expected if bubble shape preserves the record of dominant basal glide. This suggests that a method using bubbles as strain gauges could provide insights to grain-scale ice deformation. We introduce a technique using fabric and image analyses of paired thin and thick sections. Comparison of the crystallographic orientations of 148 grains and the shape orientations of 2377 intragrain bubbles reveals a strongly preferred elongation of bubbles in the grain basal planes (〈span〉R〈/span〉〈span〉2〈/span〉 = 0.96). Elongation magnitudes are consistent with a balance between ice flow deformation and diffusive restoration, with larger bubbles more elongated. Assuming bubbles record ice strain, grains with greater resolved stress on their basal planes from the far-field ice flow stresses show greater deformation, but with large variability suggesting that heterogeneity of the local stress field causes deformation even in unfavorably oriented grains. A correlation is also observed among bubble elongation, grain size, and bubble size, explaining a small but significant fraction of the variance ( 〈span〉P〈/span〉〈/p〉〈/div〉