Holocene sedimentation in the Strait of Otranto between the Adriatic and Ionian Seas (Mediterranean)

An extensive radiograph study of 24 undisturbed, up to 206-cm long box and gravity cores from the western part of the Strait of Otranto revealed a great variety of primary bedding structures and secondary burrowing features.     

La depressione dell'orizzonte marino a Genova

Riassunto Vengono discussi i risultati, espressi con le medie mensili corrispondenti, delle numerose osservazioni dell'angolo di depressione dell'orizzonte marino eseguite all'Istituto Geofisico e Geodetico dell'Università di Genova (m 55.334), ricorrendo alla formola diFreiesleben e valorizzando le contemporanee misure della temperatura dell'aria e di quella superficiale del mare, eseguite sulla costa. Si dimostra inoltre che la formola empirica dell'Ammiragliato Giapponese fornisce un buon accordo con le osservazioni di Genova.

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Summary Numerous observations of the dip of the horizon which have been carried out at the Institute for Geophysics and Geodesy of the University of Genoa (55.334 m), are discussed by using the monthly means. Using simultaneous measurements of the temperatures of the air and of the sea water at the coast, the formula ofFreiesleben was applied. Furthermore it was possible to show that the empirical formula set up by the Japanese admiralty is quite in agreement with the observations of Genoa.

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Zusammenfassung Es werden anhand von Monatsmitteln die zahlreichen Beobachtungen der Kimmtiefe diskutiert, die am Geophysikalischen und Geodätischen Institut der Universität von Genua (55.334 m) gemacht worden sind. Unter Benützung von gleichzeitigen Messungen der Lufttemperatur und der Temperatur der Meeresoberfläche an der Küste, wurden die Formeln vonFreiesleben angewandt. Es zeigte sich auch, dass die von der japanischen Admiralität aufgestellte empirische Formel gut mit den Beobachtungen von Genua übereinstimmt.

     

Future seagrass beds: Can increased productivity lead to increased carbon storage?

While carbon capture and storage (CCS) is increasingly recognised as technologically possible, recent evidence from deep-sea CCS activities suggests that leakage from reservoirs may result in highly CO₂ impacted biological communities. In contrast, shallow marine waters have higher primary productivity which may partially mitigate this leakage. We used natural CO₂ seeps in shallow marine waters to assess if increased benthic primary productivity could capture and store CO₂ leakage in areas targeted for CCS. We found that the productivity of seagrass communities (in situ, using natural CO₂ seeps) and two individual species (ex situ, Cymodocea serrulata and Halophila ovalis) increased with CO₂ concentration, but only species with dense belowground biomass increased in abundance (e.g. C. serrulata). Importantly, the ratio of below:above ground biomass of seagrass communities increased fivefold, making seagrass good candidates to partially mitigate CO₂ leakage from sub-seabed reservoirs, since they form carbon sinks that can be buried for millennia.     

Assessing future climatic changes of rainfall extremes at small spatio-temporal scales

Climate change is expected to influence the occurrence and magnitude of rainfall extremes and hence the flood risks in cities. Major impacts of an increased pluvial flood risk are expected to occur at hourly and sub-hourly resolutions. This makes convective storms the dominant rainfall type in relation to urban flooding. The present study focuses on high-resolution regional climate model (RCM) skill in simulating sub-daily rainfall extremes. Temporal and spatial characteristics of output from three different RCM simulations with 25 km resolution are compared to point rainfall extremes estimated from observed data. The applied RCM data sets represent two different models and two different types of forcing. Temporal changes in observed extreme point rainfall are partly reproduced by the RCM RACMO when forced by ERA40 re-analysis data. Two ECHAM forced simulations show similar increases in the occurrence of rainfall extremes of over a 150-year period, but significantly different changes in the magnitudes. The physical processes behind convective rainfall extremes generate a distinctive spatial inter-site correlation structure for extreme events. All analysed RCM rainfall extremes, however, show a clear deviation from this correlation structure for sub-daily rainfalls, partly because RCM output represents areal rainfall intensities and partly due to well-known inadequacies in the convective parameterization of RCMs. The results highlight the problem urban designers are facing when using RCM output. The paper takes the first step towards a methodology by which RCM performance and other downscaling methods can be assessed in relation to the simulation of short-duration rainfall extremes.     

Analysis of stick-slip and earthquake mechanism

A mathematical model of a sliding system that contains a frictional surface embedded in an elastic specimen and machine is proposed to analyze the frictional behavior observed in laboratory and field. It is shown that stick-slip occurs if the slope of the velocity-stress relation on the sliding surface exceeds a critical value at a certain point between static and kinetic frictions. This condition, coupled with Amontons' law and other subsidiary relations, predicts the effects of normal stress, gouge thickness, temperature, and loading rate etc. on the stick-slip instability, consistent with known experimental evidence. The elastic-wave radiation associated with stick-slip is governed by Brune's source time function, in which rise time and effective stress are proportional to fault dimension and stress drop, respectively.     

Reply to Discussion of “Perceptual models of uncertainty for socio-hydrological systems: a flood risk change example”*

ABSTRACT

Ertsen discusses the representation of reality and uncertainty in our paper, raising three critical points. In response to the first, we agree that discussion of different interpretations of the concept of uncertainty is important when developing perceptual models – making different uncertainty interpretations explicit was a key motivation behind our method. Secondly, we do not, as Ertsen suggests, deny anyone who is not a “certified” scientist to have relevant knowledge. The elicitation of diverse views by discussing perceptual models is a basis for open discussion and decision making. Thirdly, Ertsen suggests that it is not useful to treat socio-hydrological systems as if they exist. We argue that we act as “pragmatic realists” in most practical applications by treating socio-hydrological systems as an external reality that can be known. But the uncertainty that arises from our knowledge limitations needs to be recognized, as it may impact on practical decision making and associated costs.     

Future makers or future takers? A scenario analysis of climate change and the Great Barrier Reef

The extent to which nations and regions can actively shape the future or must passively respond to global forces is a topic of relevance to current discourses on climate change. In Australia, climate change has been identified as the greatest threat to the ecological resilience of the Great Barrier Reef, but is exacerbated by regional and local pressures. We undertook a scenario analysis to explore how two key uncertainties may influence these threats and their impact on the Great Barrier Reef and adjacent catchments in 2100: whether (1) global development and (2) Australian development is defined and pursued primarily in terms of economic growth or broader concepts of human well-being and environmental sustainability, and in turn, how climate change is managed and mitigated. We compared the implications of four scenarios for marine and terrestrial ecosystem services and human well-being. The results suggest that while regional actions can partially offset global inaction on climate change until about mid-century, there are probable threshold levels for marine ecosystems, beyond which the Great Barrier Reef will become a fundamentally different system by 2100 if climate change is not curtailed. Management that can respond to pressures at both global and regional scales will be needed to maintain the full range of ecosystem services. Modest improvements in human well-being appear possible even while ecosystem services decline, but only where regional management is strong. The future of the region depends largely on whether national and regional decision-makers choose to be active future ‘makers’ or passive future ‘takers’ in responding to global drivers of change. We conclude by discussing potential avenues for using these scenarios further with the Great Barrier Reef region's stakeholders.     

Barents-Kara sea ice and European winters in EC-Earth

Climate Dynamics - The potential link between decreasing Barents-Kara sea ice and cold winters in Europe is investigated using the enhanced resolution (horizontal atmospheric resolution of $$\sim...