Assessing potential output growth of the Maltese economy using a production function approach

After outlining the various methods used to estimate potential output, this article presents estim- ates for Malta, the smallest member of the euro area, de- rived from one of the most commonly used methods, the production function approach. Given the uncertainty surrounding these kinds of estimates, these estimates are compared with those made for Malta by other in- stitutions using di erent methods. Based on this ana- lysis and on a cross-country comparison with other euro area economies, a number of observations are made that would enable potential growth to accelerate and result in a faster economic convergence.peer-reviewe

A topographic signature of a hydrodynamic origin for submarine gullies

Submarine gullies - small scale, straight, shallow channels formed in relatively high seafloor-slope settings - are ubiquitous features that play an important role in the general evolution of continental margin morphology. The mechanisms associated with the origin and evolution of submarine gullies are, however, still poorly defined. In this paper we present evidence of a topographic signature of gully erosion in the Cook Strait sector of the Hikurangi subduction margin, New Zealand. This signature indicates that submarine gully initiation is a threshold process driven by unconfined, directionally-stable, fluid or sediment gravity flows accelerating downslope. We propose cascading dense water, a type of current that is driven by seawater density contrast, as the source of these flows. The sensitivity of such ephemeral hydrodynamic events to climate change raises questions regarding implications for future variation of the distribution and magnitude of a significant seafloor erosion process.peer-reviewe

Proposal for the nomination of Lower Globigerina Limestone of the Maltese Islands as a "Global Heritage Stone Resource"

The Lower Globigerina Limestone of the Maltese Islands is here being proposed for nomination as a “Global Heritage Stone Resource”. This stone, continuously used for building and sculpture for 6000 years, is well suited to fit this global designation as it is not only of great local cultural, historic and economic importance, but it is also the building stone used in construction of the UNESCO, and hence internationally recognized, World Heritage city of Valletta, as well as the UNESCO-listed Prehistoric Megalithic Temples of the Maltese Islands. The stone was also exported to several European and North African countries especially in the early 20 th century. The entire range of archaeological remains and historic architecture which cover the Maltese Islands have been built in this stone, and encompass innumerable palaces and churches, including the fortified cities of Valletta, Mdina (the old capital of Malta), the Three Cities on the Grand Harbour and the Citadel of Gozo, as well as the vernacular architecture ubiquitous within the village cores all over the Islands. The soft limestone has also been widely used over the millennia for elaborate and extensive sculptural motifs. Practically the only natural resource of the Islands, it continues to be quarried today, and is used not only for new construction, but also for the regular restoration of Malta’s great and imposing architectural heritage, remaining thus an important pillar of the Maltese economy.peer-reviewe

Holocene canyon activity under a combination of tidal and tectonic forcing

The majority of submarine canyon systems that are active during sea level highstands are coupled to terrestrial or littoral sediment transport systems (e.g. high sediment-yield rivers, wave-base sediment disturbance). However, non-coupled canyon systems can also exhibit sedimentary activity. Characterising the nature, origin, and spatial and temporal influence of the processes responsible for this sedimentary activity is important to understand the extent of sediment and carbon transfer to the deep sea, the impact of sedimentary flows on biological colonisation and diversity, and the control of recent seafloor processes on canyon morphology.peer-reviewe

Seismic Reflection Methods in Offshore Groundwater Research

There is growing evidence that passive margin sediments in offshore settings host large volumes of fresh and brackish water of meteoric origin in submarine sub-surface reservoirs. Marine geophysical methods, in particular seismic reflection data, can help characterize offshore hydrogeological systems and yet the existing global database of industrial basin wide surveys remains untapped in this context. In this paper we highlight the importance of these data in groundwater exploration, by reviewing existing studies that apply physical stratigraphy and morpho-structural interpretation techniques to provide important information on—reservoir (aquifer) properties and architecture, permeability barriers, paleo-continental environments, sea-level changes and shift of coastal facies through time and conduits for water flow. We then evaluate the scientific and applied relevance of such methodology within a holistic workflow for offshore groundwater research

Impact of sea level fluctuations on the sedimentation patterns of the SE African margin:Implications for slope instability

The sheared-passive margin offshore Durban (South Africa) is characterised by a narrow continental shelf and steep slope hosting numerous submarine canyons. Supply of sediment to the margin is predominantly terrigenous, dominated by discharge from several short but fast-flowing rivers. IODP Expedition 361 provides a unique opportunity to investigate the role of sea level fluctuations on the sedimentation patterns and slope instability along the South African margin. We analysed >300 sediment samples and downcore variations in P-wave, magnetic susceptibility, bioturbation intensity, and bulk density from site U1474, as well as regional seismic reflection profiles to: (i) document an increase in sand input since the mid-Pliocene; (ii) associate this change to a drop in sea level and extension of subaerial drainage systems towards the shelf-edge; (iii) demonstrate that slope instability has played a key role in the evolution of the South Africa margin facing the Natal Valley. Furthermore, we highlight how the widespread occurrence of failure events reflects the tectonic control on the morphology of the shelf and slope, as well as bottom current scour and instability of fan complexes. This information in important to improve hazard assessment in a populated coastal region with growing offshore hydrocarbon activities

Influence of erosive fluidization on the morphology of fluid flow and escape structures

Mechanisms of fluid flow localization and pockmark formation remain an open question. Many conceptual models have been proposed, but very few predictive models exist. We propose a model based on erosive fluidization where seepage induced erosion, fluidization, and transport of granular material leads the formation of fluid escape structures (FES) like pipes, chimneys and pockmarks. The model predicts: 1) formation of conical focused flow conduits with brecciated core and annular gas channels encased within a halo of low permeability sediment, 2) pockmarks of diverse shapes and sizes, including W-, U-, and ring-shapes, and 3) pulsed gas release. Results show that the morphology of FES depends on properties related to sediment-fluid interactions (like erodibility and flow anisotropy), not on intrinsic sediment properties (like permeability). Although the study is theoretical, we show that our predicted FES have many real world analogs, highlighting the broad scope of the predictive capability of our model.peer-reviewe

Characterising the ocean frontier : a review of marine geomorphometry

Geomorphometry, the science that quantitatively describes terrains, has traditionally focused on the investigation of terrestrial landscapes. However, the dramatic increase in the availability of digital bathymetric data and the increasing ease by which geomorphometry can be investigated using Geographic Information Systems (GIS) has prompted interest in employing geomorphometric techniques to investigate the marine environment. Over the last decade, a suite of geomorphometric techniques have been applied (e.g. terrain attributes, feature extraction, automated classification) to investigate the characterisation of seabed terrain from the coastal zone to the deep sea. Geomorphometric techniques are, however, not as varied, nor as extensively applied, in marine as they are in terrestrial environments. This is at least partly due to difficulties associated with capturing, classifying, and validating terrain characteristics underwater. There is nevertheless much common ground between terrestrial and marine geomorphology applications and it is important that, in developing the science and application of marine geomorphometry, we build on the lessons learned from terrestrial studies. We note, however, that not all terrestrial solutions can be adopted by marine geomorphometric studies since the dynamic, four- dimensional nature of the marine environment causes its own issues, boosting the need for a dedicated scientific effort in marine geomorphometry. This contribution offers the first comprehensive review of marine geomorphometry to date. It addresses all the five main steps of geomorphometry, from data collection to the application of terrain attributes and features. We focus on how these steps are relevant to marine geomorphometry and also highlight differences from terrestrial geomorphometry. We conclude with recommendations and reflections on the future of marine geomorphometry.peer-reviewe